WO2015080250A1 - 有機el素子の寿命推定方法、寿命推定装置及び製造方法、並びに発光装置 - Google Patents
有機el素子の寿命推定方法、寿命推定装置及び製造方法、並びに発光装置 Download PDFInfo
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- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
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- G01R31/2642—Testing semiconductor operation lifetime or reliability, e.g. by accelerated life tests
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- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
- G09G3/006—Electronic inspection or testing of displays and display drivers, e.g. of LED or LCD displays
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- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
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- G01R31/26—Testing of individual semiconductor devices
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- G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
- G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
- G09G3/22—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources
- G09G3/30—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels
- G09G3/32—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED]
- G09G3/3208—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED]
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- H—ELECTRICITY
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- H10K71/70—Testing, e.g. accelerated lifetime tests
Definitions
- the present invention relates to a lifetime estimation method, lifetime estimation apparatus and manufacturing method of an organic EL element, and a light emitting device.
- an organic EL element when used as a light source for illumination, it is required to have a life of about 40000 hours or more under standard conditions (for example, luminance of 3000 to 5000 cd / m 2 ).
- luminance 3000 to 5000 cd / m 2
- it is not practical to measure for a long time such as 40000 hours, which is not practical.
- acceleration that accelerates deterioration of the organic EL element such as significantly increasing luminance. It is common to measure life under conditions.
- Non-Patent Document 1 a method of fitting a deterioration curve of the organic EL element with a function that uses a power of an applied current density (see, for example, Non-Patent Documents 2 and 3), driving the organic EL element
- a method of fitting with a function of the ambient temperature see, for example, Non-Patent Document 1 is used.
- the organic EL element is required to suppress deterioration of the organic EL element due to use, particularly in light source applications such as illumination and display. Since it is considered that the deterioration of the organic EL element has a correlation with the temperature of the organic layer constituting the organic EL element, in order to suppress the deterioration of the organic EL element, the temperature of the organic layer can be measured accurately. It becomes important.
- Patent Document 1 previously measures the current-voltage-temperature characteristics of an organic EL element by applying a voltage signal or current signal having a pulse waveform to the organic EL element at a plurality of different ambient temperatures. A method for calculating the internal temperature of the organic EL element based on the current-voltage-temperature characteristics is disclosed.
- Non-Patent Document 1 the voltage-temperature characteristics of an organic EL element are measured in advance by applying a current signal to the organic EL element at a plurality of different ambient temperatures using a constant low current signal.
- a method for calculating the internal temperature of an organic EL element based on voltage-temperature characteristics is disclosed.
- An object of the present invention is to provide an organic EL element lifetime estimation method, a lifetime estimation apparatus and manufacturing method, and a light emitting apparatus that can accurately estimate the lifetime of the organic EL element.
- the organic EL element measured in advance as in the method disclosed in Patent Document 1 is used.
- the temperature of the deteriorated organic EL element was calculated based on the current-voltage-temperature characteristics, it was found that the accuracy of the calculated temperature was not necessarily high.
- Another object of the present invention is to provide a method for obtaining the temperature of the organic layer in the organic EL element capable of measuring the temperature of the organic layer of the organic EL element with high accuracy.
- the organic EL element lifetime estimation method is a method for estimating the lifetime of an organic EL element comprising a pair of electrodes and an organic layer disposed between the pair of electrodes.
- the organic EL element lifetime estimation method of the present invention a time-varying parameter is extracted from a fitting function of data of a time-varying element characteristic of the organic EL element, and the temperature of the time-varying parameter is calculated using a temperature rise value at the time of light emission of the organic layer.
- the lifetime estimation formula of the organic EL element is set. That is, in this method for estimating the lifetime of the organic EL element, the lifetime estimation formula is an expression that takes into account the temperature rise value during light emission of the organic layer.
- the lifetime of the organic EL element is estimated in consideration of heat generation. Therefore, according to the organic EL element lifetime estimation method of the present invention, it is possible to estimate the lifetime of the organic EL element more accurately than the conventional lifetime estimation method. Furthermore, even when the current density applied to the organic EL element is large (that is, the self-heating of the organic layer is large), this is an excellent lifetime estimation method that can accurately estimate the lifetime of the organic EL element.
- the time-varying parameters are the luminance of the organic EL element in the fitting function, the luminous intensity that is the luminous flux, the radiant flux or the number of photons, the luminous efficiency that indicates the luminous flux per unit input power, and the external that indicates the number of photons that are taken out per unit current It is preferably a coefficient of a function that characterizes the change in the quantum efficiency or the threshold voltage or the driving voltage that becomes a constant current with time. In this case, the lifetime of the organic EL element can be estimated based on characteristics that can be easily measured.
- the time-dependent parameter is corrected based on the temperature dependency, and the dependency due to other factors is derived by deriving the dependency due to other factors over time. It is preferable to set a life estimation formula including a product with a term. In this case, since the lifetime estimation formula is a formula that takes into account other factors in addition to the temperature rise value of the organic layer, the lifetime of the organic EL element can be estimated more accurately.
- the lifetime estimation formula is a formula that takes into account factors that have a large influence on the lifetime of the organic EL element, the lifetime of the organic EL element can be estimated more accurately.
- the temperature rise value is preferably a temperature rise value obtained by measuring the current-voltage characteristics of the organic EL element, measuring the transient characteristics of the light emission intensity, or measuring the Raman spectroscopy of the organic layer. In this case, since the more accurate temperature rise value of the organic layer can be used, the lifetime of the organic EL element can be estimated more accurately.
- the temperature rise value is determined by measuring the voltage between the electrodes when the organic EL element is held at each ambient temperature for a predetermined time at a plurality of ambient temperatures and a pulse current is applied to the organic EL element.
- a first step for obtaining initial information on the correlation between the voltage and the voltage a second step for driving and stopping the organic EL element, and after the second step, the organic EL element is moved under a predetermined ambient temperature T 1.
- a temperature T 1 obtained in the third step and a third step of measuring the voltage V 1 when the same pulse current as that in the first step is applied to the organic EL element.
- the fourth step of correcting the initial information based on the voltage V 1 and acquiring the correction information related to the correlation between the temperature and the voltage of the organic layer, and the same as the pulse current in the first step Measuring the voltage V 2 between the electrodes upon application of one pulse current, and a fifth step of obtaining a temperature T 2 corresponding to the voltage V 2 based on the correction information, obtained by the method comprising a temperature An increase value is preferred.
- the voltage between the electrodes when a pulse current is applied to the driven organic EL element is measured, and in the fourth step, the temperature and voltage of the organic layer measured in advance are measured. Correction information is obtained by correcting the initial information related to the correlation with the temperature and voltage of the organic layer measured in the third step. Therefore, in this method, the temperature of the organic EL element is measured based on the correlation between the temperature of the organic layer in the organic EL element after deterioration and the voltage between the electrodes. Therefore, the temperature of the organic layer can be measured with high accuracy even for an organic EL element that has deteriorated with driving.
- the above method further includes a step of driving the organic EL element with the same applied current value as the applied current value in the second step before the first step.
- the temperature of the organic layer can be measured with high accuracy even for an organic EL element in which the correlation between the temperature and voltage of the organic layer changes due to current application during driving.
- the applied current value is the same as the applied current value in the second step before applying the pulse current to the organic EL element at some or all of the plurality of ambient temperatures. It is preferable to include a step of driving the organic EL element. In this case, the temperature of the organic layer can be measured with high accuracy even for an organic EL element in which the correlation between the temperature and voltage of the organic layer changes depending on the current application during driving and the temperature of the organic layer. It becomes possible.
- the temperature rise value of the organic layer is obtained together with the time change parameter to measure the time change of the temperature rise value, and in the estimation formula setting step, the life estimation formula is calculated using the time change of the temperature rise value. It is preferable to set. In this case, since the lifetime estimation formula is a formula that takes into account the temporal change in the temperature of the organic layer, the lifetime of the organic EL element can be estimated more accurately.
- L (t) represents the emission intensity after t hours from the start of the life test of the organic EL element
- L 0 represents the light emission at the start of the life test of the organic EL element.
- a i , b, c, d, ⁇ i and ⁇ represent time-varying parameters.
- the organic EL element lifetime estimation apparatus is an organic EL element lifetime estimation apparatus that estimates the lifetime of an organic EL element, and uses the organic EL element lifetime estimation method described above to determine the lifetime of an organic EL element.
- a life estimation unit for estimation and a temperature acquisition unit for acquiring a temperature rise value are provided. According to this lifetime estimation apparatus, it becomes possible to estimate the lifetime of an organic EL element more correctly compared with the conventional lifetime estimation apparatus.
- the organic EL device manufacturing method includes a step of obtaining an organic EL device by disposing an organic layer between a pair of electrodes, and a method for estimating the lifetime of the organic EL device as described above. Using the estimation step, and comparing the estimated lifetime with a reference value of the lifetime, and determining whether the organic EL element is good or bad. According to this manufacturing method, it is possible to manufacture a non-defective organic EL element whose lifetime has been estimated more accurately than in the conventional manufacturing method.
- a light-emitting device includes an organic EL element, a lifetime estimation unit that estimates the lifetime of the organic EL element using the lifetime estimation method of the organic EL element, and a temperature acquisition unit that acquires a temperature rise value. I have. According to the present light emitting device, the lifetime of the organic EL element can be estimated and discriminated more accurately than in the conventional light emitting device.
- the temperature acquisition unit in the lifetime estimation device and the light emitting device includes a temperature control unit that controls the ambient temperature of the organic EL element, a pulse current source that applies a pulse current to the organic EL element, and a pulse current that is applied to the organic EL element.
- the temperature acquisition system may include a voltage measurement unit that measures the voltage between the pair of electrodes and an information processing unit that processes information related to the correlation between the temperature and the voltage of the organic layer.
- the light emitting device may further include a life discriminating unit that discriminates the life of the organic EL element by comparing the estimated life and the reference value of the life.
- an organic EL element lifetime estimation method it is possible to provide an organic EL element lifetime estimation method, a lifetime estimation apparatus and a manufacturing method, and a light emitting apparatus that can accurately estimate the lifetime of an organic EL element as compared with a conventional lifetime estimation method. Furthermore, even when the current density applied to the organic EL element is large (that is, the self-heating of the organic layer is large), it is possible to accurately estimate the lifetime of the organic EL element.
- a lifetime estimation device and a manufacturing method, and a light emitting device can be provided.
- the organic EL element lifetime estimation method is a method for estimating the lifetime of an organic EL element including a pair of electrodes and an organic layer disposed between the pair of electrodes.
- FIG. 1 is a diagram showing components of an organic EL element lifetime estimating apparatus according to the present embodiment.
- the lifetime estimation apparatus 1 includes, for example, a lifetime estimation unit 2, a temperature acquisition unit 3, an installation unit 5 that installs the organic EL element 4, and a drive unit 6 that drives the organic EL element 4. It has.
- the configuration of the organic EL element 4 includes a pair of electrodes and an organic layer disposed between the pair of electrodes (has two electrodes and an organic layer sandwiched between the two electrodes, and emits light when a current is applied. If it is a structure, there will be no restriction
- Examples of the configuration of the organic EL element 4 include a configuration of substrate / anode / hole injection layer / hole transport layer / light emitting layer / hole blocking layer / electron transport layer / electron injection layer / cathode.
- the hole injection layer, the hole transport layer, the light emitting layer, the hole blocking layer, the electron transport layer, and the electron injection layer can each be constituted by an organic layer.
- the installation unit 5 is composed of, for example, a thermostatic chamber capable of maintaining the temperature of the atmosphere in which the organic EL element 4 is installed (hereinafter referred to as “atmosphere temperature” or “environment temperature”) at a predetermined temperature.
- the drive unit 6 drives the organic EL element 4 by applying a predetermined direct current to the organic EL element 4.
- the lifetime estimation unit 2 estimates the lifetime of the organic EL element 4 by an organic EL element lifetime estimation method including a data acquisition step, a parameter extraction step, an estimation formula setting step, and a lifetime estimation step.
- FIG. 2 is a flowchart showing an example of the method for estimating the lifetime of the organic EL element according to this embodiment.
- the applied current density to the organic EL element and / or the environmental temperature of the organic EL element is changed, and the change over time of the element characteristics of the organic EL element at each applied current density and / or each environmental temperature is measured. Perform a life test.
- element characteristics mean emission intensity such as luminance, luminous flux, radiant flux, or number of photons.
- a current density J 0 at which the initial luminance of the organic EL element becomes a predetermined value (for example, 1000 to 5000 cd / m 2 ) is applied to the organic EL element, and the emission intensity (for example, luminance) of the organic EL element is set.
- a life test can be performed by measuring.
- data with time change of element characteristics such as light emission intensity of the organic EL element is acquired (S1 in FIG. 2).
- the life estimation unit 2 performs a parameter extraction step. From the result of the life test in the data acquisition step, it can be seen that the emission intensity of the organic EL element attenuates with the passage of time as shown by a deterioration curve C, for example, as shown in FIG.
- the vertical axis (left vertical axis) of the deterioration curve C represents the ratio L (t) / L 0 of the emission intensity L (t) after t hours to the emission intensity L 0 at the start of the life test.
- This deterioration curve C can be fitted by a fitting function represented by the following formula (1), (2) or (3), for example (S2 in FIG. 2).
- L (t) represents the emission intensity after t hours from the start of the life test of the organic EL element
- L 0 represents the light emission at the start of the life test of the organic EL element.
- a i , b, c, d, ⁇ i and ⁇ represent time-varying parameters.
- the aging parameter can be one or more than one.
- Expression (1) can be simplified by adding an initial attenuation term as shown in Expression (4) below.
- L (t) represents the emission intensity after t hours from the start of the life test of the organic EL element
- L 0 represents the emission intensity at the start of the life test of the organic EL element
- ⁇ is 0 or more and 1
- ⁇ 2 represents a time-varying parameter
- f (t) represents a function indicating an initial decay of emission intensity.
- the parameter governing the life can be ⁇ 2 .
- the deterioration curve C is fitted by, for example, a fitting function represented by the following formula (5) that embodies the formula (4).
- ⁇ , ⁇ 1 and ⁇ 2 represent time-varying parameters.
- FIG. 3 shows an example of changes over time of the first term (lower broken line whose intercept value is ⁇ ) and the second term (upper broken line whose intercept value is 1 ⁇ ) in Equation (5).
- the value of the first term is shown on the right vertical axis, and the value of the second term is shown on the left vertical axis.
- the value of the first term becomes almost zero.
- the contribution of the second term in the equation (5) becomes dominant, and ⁇ 2 is a change with time in the element characteristics of the organic EL element. It is clear that it is characterized.
- FIG. 4 shows an example of a deterioration curve of the organic EL element at each current density when the current density applied to the organic EL element is changed at a certain environmental temperature.
- Each fouling curve J 1, J 2 shown in FIG. 4, ... J 7 is a deterioration curve when applied to n times the current density J 0 ⁇ n with respect to the current density J 0 of a predetermined initial brightness is there.
- the fitting function of the temporal change data acquired in the data acquisition step is obtained, and the temporal change parameter characterizing the temporal change in the element characteristics of the organic EL element is extracted from the fitting function.
- the light emission intensity (for example, luminance) of the organic EL element is measured, and the coefficient of the light emission intensity (for example, luminance) in the fitting function is used as the temporal change parameter.
- the luminous efficiency that shows the luminous flux per unit input power the external quantum efficiency that shows the number of photons taken out per unit current, or the driving voltage that becomes the threshold or constant current
- a coefficient of the luminous flux that is the light flux, the radiant flux, or the number of photons in the fitting function, or a driving voltage that becomes a threshold value or a constant current may be used.
- the threshold value is a threshold value set as a value that is a constant multiple of the initial drive voltage, for example.
- the life estimation unit 2 performs an estimation formula setting step.
- the temperature rise value of the organic layer of the organic EL element is measured.
- the “temperature rise value of the organic layer” may be a temperature rise value of the whole organic layer of the organic EL element, for example, a temperature rise value of the light emitting layer.
- the organic layer temperature TEL is estimated from the obtained temperature rise value of the organic layer.
- the measurement of the temperature rise value of the organic layer may be performed only at the start of light emission of the organic EL element (at the start of the life test), or may be performed at a predetermined interval (for example, every 10 hours) during the life test.
- the temperature rise value of the organic layer is measured only at the start of light emission of the organic EL element (at the start of the life test)
- the value of the temperature rise value obtained by the measurement is taken for all periods during the life test. What is necessary is just to use as a temperature rise value of an organic layer.
- the temperature rise value of the organic layer is measured at a predetermined interval during the life test, the value of the temperature rise value obtained by a certain measurement is measured after the measurement.
- the temperature rise value of the organic layer can be obtained from, for example, measurement of current-voltage characteristics (IV characteristics) of the organic EL element. Specifically, the voltage between the electrodes of the organic EL element at the time of applying the current pulse is measured using a current pulse in which the temperature of the organic EL element is maintained at a constant temperature in a thermostat and the temperature rise due to driving is suppressed. By repeating this measurement while changing the temperature of the organic EL element (temperature of the thermostatic chamber), the current-voltage characteristics depending on the temperature can be acquired as a standard curve. Next, the voltage is measured by quickly applying the same current pulse as described above from the state where the organic EL element is actually driven to emit light. By comparing the voltage at the time of driving with the standard curve, the temperature rise value of the organic layer at the time of driving can be estimated.
- IV characteristics current-voltage characteristics
- the temperature rise value of the organic layer can be obtained by Raman spectroscopy measurement of the organic layer. Specifically, Raman scattered light from a specific organic layer constituting the organic EL element can be detected, and the temperature of the organic layer can be estimated using the intensity ratio of Stokes light / anti-Stokes light. In addition, the temperature of the organic EL element is kept constant in the thermostat, the wavelength shift or peak width of the Raman scattered light is measured, and this measurement is repeated while changing the temperature of the organic EL element (temperature of the thermostat). Thus, the wavelength shift or peak width depending on the temperature is acquired as a standard curve, and then the Raman scattered light is detected in a state where the organic EL element is actually driven to emit light, and the wavelength shift or peak at this time is detected. By comparing the width with the standard curve, the temperature rise value of the organic layer during driving can be estimated.
- the temperature rise value of the organic layer can be obtained from transient characteristics measurement of the emission intensity of the organic EL element. Specifically, the temperature of the organic EL element is maintained at a constant temperature in a thermostatic bath, photoluminescence from a specific organic layer constituting the organic EL element is observed using pulsed excitation light, and the time constant of the intensity attenuation is observed. To get. By repeating this measurement while changing the temperature of the organic EL element (temperature of the thermostat), a time constant depending on the temperature can be acquired as a standard curve.
- the time constant of photoluminescence is measured in the state where the organic EL element is actually driven to emit light, and the temperature rise value of the organic layer at the time of driving is compared by comparing the time constant at this time with a standard curve. Can be estimated.
- FIG. 5 also shows a curve (broken line) approximated based on these data.
- FIG. 8 shows the result of plotting the time-varying parameter ⁇ 2 obtained from the life test at each environmental temperature against the current density. Further, in FIG. 8, the relationship between the current density obtained by using Equation (6) and the time-dependent change parameter ⁇ 2 at each environmental temperature is indicated by a solid line, a broken line, or the like. As apparent from FIG. 8, the organic layer temperature T EL relationship between applied current density and aging parameter tau 2 obtained using equation (6) including the aging parameter tau 2 of the current obtained from the life test It can be seen that the density dependence is well reproduced.
- the fitting function of the temporal change data of the organic EL element in the present embodiment can be expressed by the following formula (5) that embodies the following formula (4) (S6 in FIG. 2).
- ⁇ 2 in the equations (4) and (5) can be expressed by the following equation (6).
- the lifetime estimation formula of the organic EL element is set by obtaining the temperature dependence of the time-varying parameter using the temperature rise value during light emission of the organic layer.
- the aging parameter tau 2 is set the life estimation equation based depend on the current density applied to the organic EL element to another organic layer temperature, aging parameter tau 2
- the life estimation formula may be set based on depending on the voltage applied to the organic EL element or the electric power input to the organic EL element.
- the life under the standard driving condition is estimated from the life under the acceleration condition based on the formula (4) or (5) (S7 in FIG. 2).
- the lifetime estimation unit 2 estimates the lifetime of the organic EL element 4.
- the lifetime estimation part 2 may estimate the lifetime of the organic EL element 4 by performing the flow shown in FIG. 2 once, and repeats the flow shown in FIG. A lifetime of 4 may be estimated.
- the environmental temperature is 55 ° C. or less.
- the lifetime can be evaluated within 1000 hours under the acceleration condition included in the region indicated by R. . That is, according to the method for estimating the lifetime of the organic EL element, it is possible to accurately estimate necessary acceleration conditions.
- the lifetime estimation formula is an equation that takes into consideration the temperature at which the organic layer emits light (organic layer temperature T EL ). Therefore, the lifetime of the organic EL element can be estimated in consideration of self-heating of the organic layer due to current application that affects the lifetime of the organic EL element. Therefore, in this organic EL element lifetime estimation method, it is possible to estimate the lifetime of the organic EL element more accurately than the conventional lifetime estimation method. Furthermore, even when the current density applied to the organic EL element is large (that is, the self-heating of the organic layer is large), it is possible to accurately estimate the lifetime of the organic EL element.
- the life estimation unit 2 fits the deterioration curve by the fitting function represented by the formula (1), (2), or (3) in the parameter extraction step.
- a deterioration curve of the organic EL element as shown in FIG. 10 may be fitted by a fitting function represented by the following formula (7), (8) or (9).
- Expression (7) is obtained by expanding Expression (4) along Expression (1).
- L (t), L 0 , a i , b, c, d, ⁇ i and ⁇ are represented by the formulas (1), (2) and (3).
- L (t), L 0 , a i , b, c, d, ⁇ i and ⁇ are synonymous with each other.
- ⁇ is a time-varying parameter that satisfies 0 ⁇ ⁇ 1.
- FIG. 14 shows the result of plotting the time-varying parameter ⁇ obtained from the life test at each environmental temperature against the current density. Further, in FIG. 14, the relationship between the current density obtained by using Equation (10) and the temporal change parameter ⁇ at each environmental temperature is indicated by a solid line, a broken line, or the like. As apparent from FIG. 14, the relationship between ⁇ applied current density and aging parameter obtained using Equation (10) including an organic layer temperature T EL, the current density dependence of aging parameter ⁇ obtained from life test It can be seen that the sex is well reproduced.
- the life estimation unit 2 in the life estimation apparatus 1 may have a table for deriving a temperature increase value from the applied current density and / or the environmental temperature.
- the table for deriving the temperature increase value from the applied current density and / or the environmental temperature is, for example, a conversion table for converting the applied current density and the environmental temperature into the organic layer temperature (temperature increase value) as shown in FIG. .
- the temperature acquisition part 3 in the lifetime estimation apparatus 1 may be comprised, for example from the temperature acquisition system.
- the temperature increase value obtained by the temperature acquisition system can be used as the temperature increase value.
- a temperature acquisition system is demonstrated.
- FIG. 17 is a diagram showing components of the temperature acquisition system according to the present embodiment.
- the temperature acquisition system 7 includes a temperature control unit 8, a pulse current source 9, a voltage measurement unit 10, an information processing unit 11, an installation unit 5 for installing the organic EL element 4, and an organic And a drive unit 6 for driving the EL element 4.
- the installation unit 5 and the drive unit 6 may be provided as part of the temperature acquisition system as described above, but may be provided outside the temperature acquisition system.
- the temperature control unit 8 controls the atmospheric temperature of the organic EL element 4 (for example, the temperature of the thermostatic chamber (installation unit 5)).
- the pulse current source 9 applies a pulse current to the organic EL element 4.
- the voltage measuring unit 10 is a voltage between a pair of electrodes constituting the organic EL element 4 when the pulse current source 9 applies a pulse current to the organic EL element 4 (hereinafter, also simply referred to as “interelectrode voltage”). taking measurement.
- the information processing unit 11 acquires information related to the correlation between the temperature of the organic layer measured by the voltage measurement unit 10 and the interelectrode voltage.
- the first to fifth steps are performed as follows.
- the temperature controller 8 changes the ambient temperature of the organic EL element 4 at intervals of 5 to 20 ° C., for example, between ⁇ 40 ° C. and 80 ° C.
- the temperature control unit 8 receives, for example, information from the installation unit 5 regarding whether or not the temperature of the organic EL element 4 is stable at each ambient temperature of the organic EL element 4.
- the installation unit 5 measures the temperature of the substrate surface of the organic EL element 4 using, for example, a thermocouple, and indicates that the temperature of the organic EL element 4 is stable when the temperature is held constant for 10 minutes.
- a signal is transmitted to the temperature control unit 8.
- the correlation between the interelectrode voltage and the ambient temperature can be regarded as the correlation between the interelectrode voltage and the temperature of the organic layer.
- the temperature control unit 8 transmits a signal indicating that the temperature of the organic EL element 4 has been stabilized from the installation unit 5 to the pulse current source 9, and sets the temperature of the organic layer of the organic EL element 4 to the information processing unit. 11 to send.
- the pulse current source 9 applies a pulse current to the organic EL element 4 and transmits a signal to that effect to the voltage measuring unit 10.
- the pulse current source 9 From the viewpoint of charging the capacitance of the organic EL element 4 and measuring the voltage between the electrodes with high accuracy, the pulse current source 9 generates a pulse current having a pulse width at which the current value sufficiently rises to a desired value. Apply to.
- the pulse current source 9 is preferably a pulse of 20 milliseconds or less, more preferably 10 milliseconds or less, and even more preferably 5 milliseconds or less from the viewpoint of suppressing the temperature rise of the organic layer of the organic EL element 4 due to the application of the pulse current.
- a pulse current having a width is applied to the organic EL element 4.
- the pulse current source 9 applies a pulse current having a current value set to the organic EL element 4 from the viewpoint of suppressing the temperature rise of the organic layer of the organic EL element 4 due to the application of the pulse current. If the temperature increase of the organic layer of the organic EL element 4 due to the application of the pulse current can be suppressed, the temperature dependency of the voltage between the electrodes can be obtained with high accuracy, and as a result, the temperature of the organic layer of the organic EL element 4 can be increased with higher accuracy. It can be measured.
- the pulse current source 9 supplies the pulse current to the organic EL so that the temperature rise of the organic layer of the organic EL element due to the pulse current application is sufficiently smaller than the temperature rise of the organic layer due to the current applied in the life test or the like.
- the temperature rise value of the organic layer due to the current value of the pulse current is preferably 1 ° C. or less, more preferably 0.1 ° C. or less.
- the temperature rise value of the organic layer of the organic EL element 4 includes, for example, the area where the pulse current is applied in the organic EL element 4, the thickness of the organic layer, the specific heat of the organic layer, the density of the organic layer, the amount of heat generated by the current pulse, the organic EL It can be obtained based on parameters such as the heat capacity of the element 4 (assuming the value of each parameter as necessary).
- the voltage measurement unit 10 measures the interelectrode voltage of the organic EL element 4 in synchronization with the timing when the pulse current source 9 applies the pulse current to the organic EL element 4, and transmits the measured interelectrode voltage to the information processing unit 11. To do.
- the information processing unit 11 stores the temperature of the organic layer of the organic EL element 4 received from the temperature control unit 8 and the interelectrode voltage at the temperature of the organic layer received from the information processing unit 11 in association with each other.
- the temperature control unit 8, the pulse current source 9, the voltage measurement unit 10, and the information processing unit 11 repeat the above operation to measure the interelectrode voltage at each temperature of the organic layer of the organic EL element 4. I will do it. Thereby, the information processing part 11 acquires the initial information regarding the correlation with the voltage between electrodes, and the temperature of an organic layer.
- the history of the organic EL element 4 subjected to the first step is not limited, but it is preferable that the history is aged and stabilized. Alternatively, it may have been driven for a certain period of time.
- the second step corresponds to a step of performing a life test, for example.
- the driving unit 6 drives the organic EL element 4 by applying a predetermined direct current to the organic EL element 4 and then stops driving.
- the driving conditions of the organic EL element 4 are not particularly limited, and even under normal conditions (for example, a condition where an ambient temperature is 25 ° C. and a direct current is applied such that the initial luminance of the organic EL element 4 is 3000 cd / m 2 ).
- the condition for accelerating the deterioration for example, the condition of applying a direct current so that the initial luminance of the organic EL element 4 is 30000 cd / m 2 at an atmospheric temperature of 55 ° C. may be used.
- a third step is performed.
- the temperature of the organic layer is maintained at the predetermined temperature T 1 by maintaining the atmospheric temperature of the organic EL element 4 at the predetermined temperature T 1 .
- the temperature T 1 of the organic layer of the organic EL element 4 is preferably set to 50 ° C. or more from the viewpoint of stabilizing the correlation between the interelectrode voltage and the temperature of the organic layer.
- one or more steps such as irradiating the device with ultraviolet light or applying a reverse bias voltage may be used for this step.
- the pulse current source 9 applies a pulse current to the organic EL element 4 and transmits a signal to that effect to the voltage measuring unit 10.
- the pulse current applied to the organic EL element 4 by the pulse current source 9 is a pulse current having the same pulse width and current value as the pulse current applied in the first step.
- the pulse current source 9 in synchronism with the timing of applying a pulse current to the organic EL device 4 measures the inter-electrode voltage V 1 of the organic EL element 4, the information processing inter-electrode voltages V 1 measured To the unit 11.
- the third step only one inter-electrode voltage at one temperature may be measured, or a plurality of inter-electrode voltages at a plurality of different temperatures may be measured.
- a fourth step is performed.
- the information processing section 11 uses the temperature T 1 of the organic layer of the organic EL element 4 received from the temperature control section 8 and the interelectrode voltage V 1 received from the voltage measurement section 10 as the first step. compared acquired the initial calibration curve L1 in step, the temperature T 1 and the inter-electrode voltage V 1 of the initial calibration curve L1 shift amount corresponding corrected calibration curve shifting the initial calibration curve L1 and from L2 (correction information) To get. More specifically, as shown in FIG. 18, an amount corresponding initial calibration of the shift amount S with respect to the initial calibration curve L1 of the inter-electrode voltage V 1 of the plots in the temperature T 1 of the organic layer (squares in Fig. 18) L1 A corrected calibration curve L2 is obtained by shifting the whole.
- the information processing unit 11 is based on the measured interelectrode voltages V 1 at the temperatures T 1 of the plurality of organic layers.
- the correction calibration curve L2 can be acquired. In this case, the information processing unit 11 can acquire the corrected calibration curve L2 with higher accuracy.
- the pulse current source 9 applies a pulse current to the organic EL element 4, and the voltage V 2 between the electrodes is measured by the voltage measuring unit 10. Measure.
- the pulse current applied to the organic EL element 4 by the pulse current source 9 is a pulse current having the same pulse width and current value as the pulse current applied in the first step.
- the voltage measuring unit 10 transmits the measured interelectrode voltage V 2 to the information processing unit 11.
- the information processing unit 11 acquires the temperature T 2 of the organic layer of the organic EL element 4 corresponding to the inter-electrode voltage V 2 based on the correction calibration curve L2. Specifically, for example, as shown in FIG. 18, the organic layer of the organic EL element 4 corresponding to the interelectrode voltage V 2 (triangle mark in FIG. 18) on the correction calibration curve L2 obtained in the fourth step. temperature T 2 can be obtained. In addition, a 5th step is suitably performed after the 2nd step according to the timing which wants to acquire the temperature of an organic layer.
- the temperature acquisition system 7 measures the voltages V 1 between the electrodes when a voltage measuring unit 10 and applying a pulse current to the organic EL element after driving, the information processing unit 11 is measured in advance
- the correction information is obtained by correcting the initial information regarding the correlation between the temperature and the voltage of the organic layer based on the temperature T 1 and the voltage V 1 of the organic layer. Therefore, the temperature measurement of the organic EL element 4 is performed based on the correlation between the temperature of the organic layer in the organic EL element 4 after deterioration and the voltage between the electrodes. Therefore, the temperature of the organic layer can be measured with high accuracy even for the organic EL element 4 that has deteriorated as a result of driving.
- a step (preliminary drive step) of driving the organic EL element 4 with the same applied current value as the applied current value in the second step may be performed before the first step.
- the drive unit 6 drives the organic EL element 4 with an applied current value that is the same as the applied current value in the second step, for example, for 1 to 60 minutes.
- the correlation between the voltage between the electrodes and the temperature of the organic layer even when the current is applied for a short time regardless of whether or not the current is applied for a long time in a life test or the like. May be shifted to the high voltage side or the low voltage side.
- the shift amount may change depending on the applied current value for a relatively short time. Therefore, for such an organic EL element, it is preferable to obtain an initial calibration curve considering the influence of current application itself. Note that the preliminary drive step can be omitted for an organic EL element in which the shift of the calibration curve due to a short-time current application is small.
- the first step may include a preliminary driving step. That is, the first step is after the organic EL element is held for a predetermined time at a part or all of the plurality of ambient temperatures and before the pulse current is applied to the organic EL element. There may be included a step of driving the organic EL element with the same applied current value as the applied current value in this step.
- the initial calibration considering the applied current value and the organic layer temperature for the organic EL element in which the shift amount of the calibration curve due to the short-time current application described above depends on the organic layer temperature in addition to the applied current value. A line can be acquired.
- the organic EL element is held at each atmospheric temperature for a predetermined time, and the voltage between the electrodes when a pulse current is applied to the organic EL element is measured.
- a step (step 1a) of obtaining initial information regarding the correlation between temperature and the voltage may be performed, (Ii) After holding the organic EL element at each ambient temperature for a predetermined time at all of the plurality of ambient temperatures, driving the organic EL element with the same applied current value as the applied current value in the second step, and then The step (step 1b) of obtaining initial information regarding the correlation between the temperature of the organic layer and the voltage may be performed by measuring the voltage between the electrodes when a pulse current is applied to the organic EL element. (Iii) Step 1a may be performed at a part of the plurality of ambient temperatures, and Step 1b may be performed at the other part of the plurality of ambient temperatures.
- the preliminary driving step may be performed after the second step or the third step, for example, and then the initial information may be acquired again.
- the temperature of the organic layer can be measured with high accuracy even for the organic EL element 4 in which the correlation between the voltage between the electrodes and the temperature of the organic layer changes due to the current application itself.
- the organic EL element manufacturing method includes the steps of obtaining an organic EL element by arranging an organic layer between a pair of electrodes, and the lifetime of the organic EL element described above. A step of estimating using an estimation method, and a step of comparing the estimated lifetime with a reference value of the lifetime and determining the quality of the obtained organic EL element.
- the light emitting device has the same configuration as that of the organic EL element lifetime estimation device shown in FIG. That is, the light-emitting device includes an organic EL element, a lifetime estimation unit that estimates the lifetime of the organic EL element using the above-described organic EL element lifetime estimation method, and a temperature acquisition unit that acquires a temperature rise value. Yes.
- Examples of such a light emitting device include a display device and a lighting device.
- the life estimation unit may have a table for deriving a temperature rise value from the applied current density and / or the environmental temperature.
- the temperature acquisition unit may be configured from the temperature acquisition system shown in FIG.
- the light emitting device may further include a life determining unit that determines the life of the organic EL element by comparing the estimated life with a reference value of the life.
- the light emitting device may further include a control unit that controls the driving condition of the organic EL element based on the temperature of the organic EL element obtained by the temperature acquisition unit or the lifetime of the organic EL element obtained by the lifetime estimation unit. Good. In this case, the driving condition of the organic EL element can be controlled to a suitable condition according to the measured temperature or lifetime of the organic EL element.
- Example 1 First, an organic EL element was produced. Specifically, a hole injection layer and a hole transport layer were formed on a glass substrate on which an ITO pattern was formed by a vacuum evaporation method, and a light emitting layer was further formed by a vacuum evaporation method by co-evaporation. Subsequently, a hole blocking layer, an electron transport layer, and an electron injection layer were similarly formed by a vacuum deposition method, and finally a cathode made of aluminum was formed. The organic EL layer produced in this way was sealed in a glove box held in an inert gas so as not to be exposed to the atmosphere to obtain an organic EL element. Table 1 shows the materials used for each layer and the film thickness of each layer.
- the produced organic EL device was placed in a thermostatic chamber, a constant current was applied to the organic EL device, and a change in luminance of the organic EL device with time was measured to perform a life test.
- Applied current density the initial luminance of the organic EL element is 1,800 cd / m 2 and comprising current density n times the current density with respect to J 0 J 0 ⁇ n (J 1, J 2, ... J 7) was.
- the correspondence between current densities J 1 , J 2 ,... J 7 and n is as follows.
- the change over time in the luminance of the organic EL element when the life test is performed under the conditions of a temperature in a thermostatic chamber: 25 ° C. and an applied current density: J 2 is a deterioration curve C shown in FIG. It was.
- the vertical axis of the deterioration curve C represents the ratio L (t) / L 0 of the luminance L (t) after t hours to the luminance L 0 at the start of the life test.
- This deterioration curve C could be fitted by a fitting function represented by the following formula (5).
- ⁇ 1 and ⁇ 2 represent time-varying parameters.
- FIG. 2 also shows temporal changes of the first term (lower broken line with intercept value ⁇ ) and the second term (upper broken line with intercept value 1 ⁇ ) in equation (5). ing. As is clear from FIG. 2, it was found that the value of the first term becomes almost zero after about 100 hours.
- FIG. 3 shows a deterioration curve of the organic EL element at each applied current density J 1 , J 2 ,... J 7 at an environmental temperature of 25 ° C. In the semi-log plot of FIG. 3, after about 100 hours, it has been found that the deterioration curves J 1 , J 2 ,... J 7 are all straight lines.
- the temperature rise value of the organic layer was measured before lifetime test implementation. Specifically, the temperature rise value of the organic layer was determined by measuring the current-voltage characteristics (IV characteristics) of the following organic EL elements.
- the organic layer temperature T EL was estimated by using the temperature rise value of the organic layer obtained from the IV characteristic is plotted against current density to be applied to the organic EL device was the plot shown in FIG. FIG. 4 also shows a curve (broken line) approximated based on these data.
- (tau) 2 is represented by following formula (6).
- A represents a positive number.
- ⁇ was 1.16 and Ea was 0.42.
- FIG. 7 shows the result of plotting the time-varying parameter ⁇ 2 obtained from the life test at each temperature in the thermostat against the current density. Further, in FIG. 7, the relationship between the current density obtained using the equation (2) and the temporal change parameter ⁇ 2 at each environmental temperature is indicated by a solid line, a broken line, or the like. As apparent from FIG. 7, the relationship between the applied current density and aging parameter tau 2 obtained using equation (6) containing organic layer temperature T EL is the aging parameter tau 2 obtained from the life test It was found that the current density dependency was well reproduced.
- the fitting function of the temporal change data of the organic EL element in this example can be expressed by the following formula (5), and ⁇ 2 in the formula (5) can be expressed by the following formula (6). I understood.
- FIG. 16 shows the relationship of the time-varying parameter ⁇ 2 with respect to the current density obtained by using the conventional method for estimating the lifetime of the organic EL element.
- Example 2 A life test was performed on the organic EL device produced in the same manner as in Example 1 by measuring the change in luminance over time in the same manner as in Example 1.
- Equation (12) b, ⁇ , ⁇ , and ⁇ ′ represent time-varying parameters.
- b was 0.7 ⁇ 0.05.
- (tau) is represented by following formula (10).
- A represents a positive number.
- ⁇ was 1.30 ⁇ 0.10 and Ea was 0.36 ⁇ 0.02.
- FIG. 14 shows the result of plotting the time-varying parameter ⁇ obtained from the life test at each temperature in the thermostat against the current density. Further, in FIG. 14, the relationship between the current density obtained using Equation (12) and the time-varying parameter ⁇ at each environmental temperature is indicated by a solid line, a broken line, or the like. As apparent from FIG. 14, the current density of the relationship between Equation (10) applied current density and aging parameters determined using the ⁇ containing organic layer temperature T EL is aging parameters obtained from the life test ⁇ It turns out that the dependency is well reproduced.
- the lifetime of the organic EL element (time until 70% of the initial luminance is reached) is predicted from the above fitting function, it is 4401 hours, which is in good agreement with the actual measured value of 4750 hours of the organic EL element. It was.
- Example 3 Next, an example of a temperature acquisition method for an organic EL element using the temperature acquisition system shown in FIG. 17 will be described.
- an organic EL element was produced. Specifically, a hole injection layer and a hole transport layer were formed on a glass substrate on which an ITO pattern was formed by a vacuum evaporation method, and a light emitting layer was further formed by a vacuum evaporation method by co-evaporation. Subsequently, a hole blocking layer, an electron transport layer, and an electron injection layer were similarly formed by a vacuum deposition method, and finally a cathode made of aluminum was formed.
- the organic EL layer produced in this way was sealed in a glove box held in an inert gas so as not to be exposed to the atmosphere to obtain an organic EL element.
- the light emitting area of the obtained organic EL element was 2 mm square. Table 3 shows the materials used for each layer and the film thickness of each layer.
- the ambient temperature Ta (the temperature T EL of the organic layer) is changed between ⁇ 35 ° C. and 80 ° C. with respect to the obtained organic EL element, and a pulse current is applied to the organic EL element at each ambient temperature Ta the inter-electrode voltage V F was measured.
- the pulse width of the pulse current was 20 ms, and the current value was 2 ⁇ A.
- the temperature rise of the organic layer of the organic EL element due to the application of the pulse current is estimated to be about 0.7 ° C.
- the organic EL element was driven for 12 hours under the conditions of an atmospheric temperature of 25 ° C. and an applied current of 2 mA.
- a pulse current having a pulse width of 20 ms and a current value of 2 ⁇ A was applied to the organic EL element after driving, and the interelectrode voltage VA was measured to be 5.11 V.
- V F interelectrode voltage
- V F interelectrode voltage
- a corrected calibration curve L4 shown in FIG. 19 was obtained.
- the corrected calibration curve L4 was shifted to the high voltage side by about 0.14 V with respect to the initial calibration curve L3.
- the organic layer temperature at an applied current of 2 mA was estimated using this calibration curve, and found to be 41 ° C.
- FIG. 21 is a diagram showing the relationship between the interelectrode voltage, the applied current value, and the ambient temperature.
- (A), (b), and (c) of FIG. 21 show the interelectrode voltage measured after applying current to the organic EL element at each applied current value at atmospheric temperatures of ⁇ 35 ° C., ⁇ 5 ° C., and 25 ° C., respectively.
- V F is shown.
- the shift amount of the inter-electrode voltage V F according to current application itself has been found to depend on the applied current value and the ambient temperature.
- FIG. 22 is a diagram showing the relationship between the applied current value and the change in the calibration curve.
- FIG. 22B is an enlarged view of FIG.
- L7 when current is not applied
- L8 when current is applied at 0.1 mA
- L9 when current is applied at 1 mA
- L10 A calibration curve for (L10) is shown.
- the temperature measurement error of the organic EL element is about 7 ° C. at the maximum when the element temperature is around 0 ° C. (L7 and L10 Difference).
- the organic layer temperature at an applied current of 1 mA at an ambient temperature of 25 ° C. was estimated to be 36 ° C.
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Abstract
Description
J1:n=0.5、J2:n=1、J3:n=2、J4:n=3、
J5:n=5、J6:n=7、J7:n=10
(i)複数の雰囲気温度の全部において、有機EL素子を各雰囲気温度下で所定時間保持し、有機EL素子にパルス電流を印加したときの前記電極間の電圧を測定することにより、有機層の温度と前記電圧との相関に関する初期情報を取得するステップ(ステップ1a)を行ってもよく、
(ii)複数の雰囲気温度の全部において、有機EL素子を各雰囲気温度下で所定時間保持した後に、第2のステップにおける印加電流値と同一の印加電流値で有機EL素子を駆動し、さらにその後に有機EL素子にパルス電流を印加したときの前記電極間の電圧を測定することにより、有機層の温度と前記電圧との相関に関する初期情報を取得するステップ(ステップ1b)を行ってもよく、
(iii)複数の雰囲気温度のうち一部においてステップ1aを行い、複数の雰囲気温度のうちその他の一部においてステップ1bを行ってもよい。
まず、有機EL素子を作製した。具体的には、ITOパターンが形成されたガラス基板上に、正孔注入層、正孔輸送層を真空蒸着法によって成膜し、さらに発光層を共蒸着による真空蒸着法によって成膜した。引き続き、正孔阻止層、電子輸送層及び電子注入層を同様に真空蒸着法によって成膜し、最後にアルミニウムからなる陰極を成膜した。このように作製した有機EL層を、大気に晒さないように不活性気体中で保持されたグローブボックス中で封止し、有機EL素子とした。なお、各層に用いた材料及び各層の膜厚を表1に示している。
J1:n=0.5、J2:n=1、J3:n=2、J4:n=3、
J5:n=5、J6:n=7、J7:n=10
また、恒温槽内の温度(有機EL素子の環境温度)は、10℃、25℃、40℃、55℃とした。表2では、恒温槽内の温度の各条件に対して実施した印加電流密度の条件を示している。
有機EL素子の温度を恒温槽中で一定温度に保ち、駆動による温度上昇を抑制した電流パルスを用いて、電流パルス印加時の電圧を測定した。有機EL素子の温度(恒温槽の温度)を変化させながらこの測定を繰り返すことにより、温度に依存する電流-電圧特性を標準曲線として取得した。次に、実際に有機EL素子を駆動し発光させている状態から速やかに上記と同様の電流パルスを印加して電圧を測定した。この駆動時の電圧と標準曲線とを比較することにより、駆動時の有機層の温度上昇値を見積もった。
実施例で実施した有機EL素子の寿命試験の結果に対して、従来の有機EL素子の寿命推定方法を用いて電流密度に対する経時変化パラメータτ2の関係を求めた。具体的には、従来の有機EL素子の寿命推定方法では、加速条件(例えばJ=J7(n=10))における寿命試験の結果に基づいて経時変化パラメータτ2(n=10)を算出した上で、経時変化パラメータτ2が電流密度のベキ乗に比例すると仮定した寿命推定式を用いて、標準条件(J=J2(n=1))における経時変化パラメータτ2(n=1)を求めた。すなわち、従来の有機EL素子の寿命推定方法では、下記式(11)で表される寿命推定式を用いた。
実施例1と同様にして作製した有機EL素子に対して、実施例1と同様に輝度の経時変化を測定することで寿命試験を行った。印加電流密度は、電流密度5mA/cm2に対してn倍の電流密度(n=1,2,3,5,7,10)とした。
続いて、図17に示した温度取得システムを用いた有機EL素子の温度取得方法の実施例を示す。
Claims (17)
- 一対の電極と、該一対の電極間に配置された有機層と、を備える有機EL素子の寿命推定方法であって、
前記有機EL素子への印加電流密度及び/又は前記有機EL素子の雰囲気温度を変化させた際の、前記有機EL素子の素子特性の経時変化データを取得するデータ取得ステップと、
前記経時変化データのフィッティング関数を求め、該フィッティング関数から前記印加電流密度及び/又は前記雰囲気温度における前記素子特性の経時変化を特徴づける経時変化パラメータを抽出するパラメータ抽出ステップと、
前記印加電流密度及び/又は前記雰囲気温度における前記有機層の発光時の温度上昇値を用いて前記経時変化パラメータの温度依存性を算出し、前記有機EL素子の寿命推定式を設定する推定式設定ステップと、
前記寿命推定式を用いて前記有機EL素子の寿命を推定する寿命推定ステップと、
を備える、有機EL素子の寿命推定方法。 - 前記経時変化パラメータが、前記フィッティング関数における、前記有機EL素子の輝度、光束、放射束若しくはフォトン数である発光強度、単位投入電力あたりの光束を示す発光効率、単位電流あたり外部に取り出されるフォトン数を示す外部量子効率、又は、閾値若しくは一定電流となる駆動電圧、の経時変化を特徴づける関数の係数である、請求項1に記載の有機EL素子の寿命推定方法。
- 前記推定式設定ステップにおいて、前記温度依存性に基づいて前記経時変化パラメータを補正し、前記経時変化パラメータの他の因子による依存性を導出することによって、前記温度依存性を表す項と前記他の因子による依存性を表す項との積を含む前記寿命推定式を設定する、請求項1又は2に記載の有機EL素子の寿命推定方法。
- 前記他の因子が、前記有機EL素子に対する前記印加電流密度、印加電圧又は投入電力である、請求項3に記載の有機EL素子の寿命推定方法。
- 前記温度上昇値が、前記有機EL素子の電流-電圧特性測定若しくは発光強度の過渡特性測定、又は、前記有機層のラマン分光測定によって得られた温度上昇値である、請求項1~4のいずれか一項に記載の有機EL素子の寿命推定方法。
- 前記温度上昇値が、
複数の雰囲気温度において、前記有機EL素子を各雰囲気温度下で所定時間保持し、前記有機EL素子にパルス電流を印加したときの前記電極間の電圧を測定することにより、前記有機層の温度と前記電圧との相関に関する初期情報を取得する第1のステップと、
前記有機EL素子の駆動及び停止を行う第2のステップと、
前記第2のステップの後に、前記有機EL素子を所定の雰囲気温度T1下で所定時間保持し、有機EL素子に前記第1のステップにおけるパルス電流と同一のパルス電流を印加したときの電圧V1を測定する第3のステップと、
前記第3のステップで得られた温度T1及び電圧V1に基づいて前記初期情報を補正し、前記有機層の温度と前記電圧との相関に関する補正情報を取得する第4のステップと、
前記有機EL素子に前記第1のステップにおけるパルス電流と同一のパルス電流を印加したときの前記電極間の電圧V2を測定し、前記補正情報に基づいて電圧V2に対応する温度T2を取得する第5のステップと、
を備える方法によって得られた温度上昇値である、請求項1~4のいずれか一項に記載の有機EL素子の寿命推定方法。 - 前記第1のステップの前に、前記第2のステップにおける印加電流値と同一の印加電流値で前記有機EL素子を駆動するステップを更に備える、請求項6に記載の有機EL素子の寿命推定方法。
- 前記第1のステップが、前記複数の雰囲気温度のうち一部又は全部の雰囲気温度において、前記有機EL素子にパルス電流を印加する前に、前記第2のステップにおける印加電流値と同一の印加電流値で前記有機EL素子を駆動するステップを含む、請求項6に記載の有機EL素子の寿命推定方法。
- 前記データ取得ステップにおいて、前記経時変化パラメータと共に前記有機層の温度上昇値を取得することで、前記温度の経時変化を測定し、
前記推定式設定ステップにおいて、前記温度上昇値の経時変化を用いて前記寿命推定式を設定する、請求項1~8のいずれか一項に記載の有機EL素子の寿命推定方法。 - 有機EL素子の寿命を推定する有機EL素子の寿命推定装置であって、
請求項1~11のいずれか一項に記載の有機EL素子の寿命推定方法を用いて前記有機EL素子の寿命を推定する寿命推定部と、
前記温度上昇値を取得する温度取得部と、
を備える、有機EL素子の寿命推定装置。 - 前記温度取得部が、
前記有機EL素子の雰囲気温度を制御する温度制御部と、
前記有機EL素子にパルス電流を印加するパルス電流源と、
前記パルス電流を前記有機EL素子に印加したときの前記一対の電極間の電圧を測定する電圧測定部と、
前記有機層の温度と前記電圧との相関に関する情報を処理する情報処理部と、を備える温度取得システムで構成されている、請求項12に記載の寿命推定装置。 - 一対の電極間に有機層を配置して有機EL素子を得るステップと、
前記有機EL素子の寿命を請求項1~11のいずれか一項に記載の有機EL素子の寿命推定方法を用いて推定するステップと、
推定された前記寿命と寿命の基準値とを比較し、前記有機EL素子の良否を判定するステップと、
を備える、有機EL素子の製造方法。 - 有機EL素子と、
請求項1~11のいずれか一項に記載の有機EL素子の寿命推定方法を用いて前記有機EL素子の寿命を推定する寿命推定部と、
前記温度上昇値を取得する温度取得部と、
を備える、発光装置。 - 前記温度取得部が、
前記有機EL素子の雰囲気温度を制御する温度制御部と、
前記有機EL素子にパルス電流を印加するパルス電流源と、
前記パルス電流を前記有機EL素子に印加したときの前記一対の電極間の電圧を測定する電圧測定部と、
前記有機層の温度と前記電圧との相関に関する情報を処理する情報処理部と、を備える温度取得システムで構成されている、請求項15に記載の発光装置。 - 推定された前記寿命と寿命の基準値とを比較して前記有機EL素子の寿命を判別する寿命判別部を更に備える、請求項15又は16に記載の発光装置。
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US10748497B2 (en) * | 2016-12-27 | 2020-08-18 | Semiconductor Energy Laboratory Co., Ltd. | Light-emitting element, light-emitting device, electronic device, and lighting device |
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US11587503B2 (en) * | 2020-11-11 | 2023-02-21 | Novatek Microelectronics Corp. | Method of and display control device for emulating OLED degradation for OLED display panel |
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