WO2015106061A1

WO2015106061A1 - Optoelectronic devices and applications thereof

Info

Publication number: WO2015106061A1
Application number: PCT/US2015/010758
Authority: WO
Inventors: Carl RYDEN
Original assignee: Purelux Inc.
Priority date: 2014-01-09
Filing date: 2015-01-09
Publication date: 2015-07-16

Abstract

In one aspect, methods of making electroluminescent devices are described herein. A method described herein comprises providing an electroluminescent phase between a first electrode and second electrode, the electroluminescent phase comprising a layer of first polycrystalline matrix and migrating an atomic species in the first polycrystalline matrix by application of an electric field to the first polycrystalline matrix. The migrating atomic species form semiconducting regions in the first polycrystalline matrix, the semiconducting regions constituents of p-n junctions of the electroluminescent phase.

Description

OPTOELECTRONIC DEVICES AND APPLICATIONS THEREOF

RELATED APPLICATION DATA

The present application claims priority to United States Provisional Patent Application Serial Number 61/925,497 filed January 9, 2014 which is incorporated herein by reference in its entirety.

FIELD

The present invention relates to optoelectronic devices and, in particular, to

electroluminescent lighting devices. Photovoltaic devices are also described herein.

BACKGROUND

Currently available lighting systems include incandescent, fluorescent, halogen, and high intensity discharge sources of light. Disadvantages exist within lighting systems based on these illumination sources, many related to efficiency. Presently, only about 30% of the electrical energy consumed in lighting applications results in the production of light. The remainder of the electrical energy is dissipated by non-radiative processes such as heat generation. Incandescent light sources, for example, consume 45% of all lighting energy but only produce 14% of the total light generated. Moreover, fluorescent lamps are only about four times as efficient as incandescent sources and still suffer from inherent energy loss.

New lighting technologies are being developed in attempts to overcome the

disadvantages of current lighting systems. One such technology is based on light emitting diodes (LEDs). In general, light emitting diodes are constructed from semiconductor materials and, when forward biased, emit radiation. Depending on the semiconductor material used, the emitted radiation can fall within the ultraviolet, visible or infrared region of the electromagnetic spectrum. Light emitting diodes offer the advantages of enhanced lifetimes, reduced heat production, and rapid illumination times.

However, light emitting diodes require a direct current source for operation, which is fundamentally inconsistent with the alternating current provided by residential and commercial electrical outlets. As a result, various rectifier constructions are necessary to adapt present light emitting diodes to the alternating current sources found in residential and commercial lighting applications. The necessity of a rectifier increases production time and cost for lighting systems incorporating light emitting diodes, thereby limiting widespread application of such lighting systems.

Electroluminescent devices compatible with alternating current sources have also been developed. These devices generally employ powder phosphor for light generation under an applied alternating electric field. While cost effective to produce, AC powder electroluminescent devices suffer dimming effects stemming from phosphor degradation. Additionally, phosphors can demonstrate widely heterogeneous micro structure further contributing to reduced light output. SUMMARY

In one aspect, methods of making electroluminescent devices are described herein which, in some embodiments, mitigate disadvantages of prior AC powder electroluminescent devices. A method described herein comprises providing an electroluminescent phase between a first electrode and second electrode, the electroluminescent phase comprising a layer of first polycrystalline matrix and migrating an atomic species in the first polycrystalline matrix by application of an electric field to the first polycrystalline matrix. The migrating atomic species form semiconducting regions in the first polycrystalline matrix, the semiconducting regions constituents of p-n junctions of the electroluminescent phase. For example, in some

embodiments, the migrating atomic species aggregate in one or more regions of the first polycrystalline matrix, such as in grain boundaries and/or at sites of crystalline defects.

Aggregation of the migrating atomic species renders these regions of the first polycrystalline matrix p-type or n-type semiconductor, wherein these semiconducting regions are constituents of p-n junctions of the electroluminescent phase.

In another aspect, methods of making photovoltaic devices are described herein. A method of making a photovoltaic device comprises providing a photosensitive phase between a first electrode and second electrode, the photosensitive phase comprising a layer of first polycrystalline matrix and migrating an atomic species in the first polycrystalline matrix by application of an electric field to the first polycrystalline matrix. The migrating atomic species form semiconducting regions in the first polycrystalline matrix, the semiconducting regions constituents of p-n junctions of the photosensitive phase. Further, the semiconducting regions can also function as light absorption regions of the photosensitive phase. These and other embodiments are described in greater detail in the detailed description which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 illustrates light emission from p-n junctions of an electroluminescent device formed according to a method described herein.

DETAILED DESCRIPTION

Embodiments described herein can be understood more readily by reference to the following detailed description and examples and their previous and following descriptions. Elements, apparatus and methods described herein, however, are not limited to the specific embodiments presented in the detailed description and examples. It should be recognized that these embodiments are merely illustrative of the principles of the present invention. Numerous modifications and adaptations will be readily apparent to those of skill in the art without departing from the spirit and scope of the invention.

I. Methods of Making Electroluminescent Devices

In one aspect, methods of making electroluminescent devices are described herein. A method described herein comprises providing an electroluminescent phase between a first electrode and second electrode, the electroluminescent phase comprising a layer of first polycrystalline matrix and migrating an atomic species in the first polycrystalline matrix by application of an electric field to the first polycrystalline matrix. The migrating atomic species form semiconducting regions in the first polycrystalline matrix, the semiconducting regions constituents of p-n junctions of the electroluminescent phase. For example, in some

embodiments, the migrating atomic species aggregate in one or more regions of the first polycrystalline matrix. Aggregation of the migrating atomic species renders these regions of the first polycrystalline matrix p-type or n-type semiconductor, wherein these semiconducting regions are constituents of p-n junctions of the electroluminescent phase.

The first polycrystalline matrix can be of the formula MiX], wherein Mi is selected from the group consisting of metallic elements including transition metals and Xi is selected from the group consisting of non-metallic elements of Groups IV A, VA and VIA of the Periodic Table. M_\, for example, can be selected from metallic elements of Groups IB, IIB and IIIA of the Periodic Table. Groups of the Periodic Table described herein are identified according to the CAS designation. In some embodiments, Mi is the sole migrating atomic species under the applied electric field. In other embodiments, atomic species in addition to Mi may migrate, such as other cationic metallic atomic species and/or anionic species in the first polycrystalline matrix. Alternatively, migrating atomic species are not of the species forming the lattice of the first polycrystalline matrix. In such embodiments, the migrating atomic species can comprise cationic and/or anionic dopants such as cationic metals, halides or chalcogenides.

The first polycrystalline matrix can have any thickness not inconsistent with the objectives of the present invention. In some embodiments, the first polycrystalline matrix can have thickness selected from Table I.

Table I - Thickness of First Polycrystalline Matrix

< 1 μηι

50 nm - 800 run

100 nm - 500 nm

75 nm - 300 nm

100 m - 200 nm

1 μ^ηι As a non-limiting example, the first polycrystalline matrix can comprise Cu_xS. When the first polycrystalline matrix is formed of Cu_xS, cationic Cu can be the migrating atomic species. Under the applied electric field, cationic Cu can migrate in the polycrystalline matrix forming regions of Cu_xS having stoichiometry of p-type semiconductor. In such embodiments, p-type regions of semiconducting Cu_xS have a stoichiometry wherein x ranges from 1.8-2.

Semiconducting regions of the first polycrystalline matrix can form p-n junctions with a layer of second polycrystalline semiconductor matrix adjacent to the first polycrystalline matrix. The second polycrystalline semiconductor matrix can be formed of compound semiconductor of opposite polarity of the semiconducting regions to form the p-n junctions. In some

embodiments, the second polycrystalline semiconductor matrix is of the formula M₂X₂, wherein M₂ is selected from the group consisting of metallic elements including transition metals and X₂ is selected from the group consisting of non-metallic elements of Groups IVA, VA and VIA of the Periodic Table. M₂, for example, can be selected from metallic elements of Groups IB, IIB and III A of the Periodic Table.

Further, the second polycrystalline semiconductor matrix can comprise one or more dopants and/or luminescent centers for providing radiation recombination of carriers received from the semiconducting regions of the first polycrystalline matrix. Luminescent centers are sites or locations in the second semiconductor matrix where charge carriers are relaxed by one or more radiative pathways. Luminescent centers can include defects or trap states for localizing injected charge carriers for radiative recombination.

Luminescent centers can also include one or more atomic species doped or otherwise incorporated into the lattice and/or interstitial sites of the semiconductor matrix as an activator. Suitable activators include ions of transition metals, rare earth metals or mixtures thereof. In some embodiments, for example, activator of the second semiconductor matrix comprises one or more metal ions selected from Groups IB, IIIB, VIIB, VIIIB and IIIA of the Periodic Table. Activator, in some embodiments, comprises ions of copper, manganese, silver, gadolinium, dysprosium, europium, samarium, terbium or thulium or mixtures thereof.

Additionally, the second semiconductor matrix can further comprise co-activator chemical species. Co-activator chemical species work in conjunction with activator for the relaxation of carriers by one or more radiative pathways. Co-activator can comprise ionic species selected from Groups IIIA and VIIA of the Periodic Table. For example, co-activator can comprise ions of aluminum, indium, chlorine or iodine or mixtures thereof. In some embodiments, co-activator can be present in the second semiconductor matrix in the absence of activator. In such embodiments, the co-activator can assist in self-radiative relaxation processes of the second semiconductor matrix in response to carriers introduced by semiconducting regions of the first polycrystalline matrix.

The specific identity and amount of activator incorporated inter stitially or into the lattice of the second semiconductor matrix for the establishment of luminescent centers can be selected according to several factors, including the chemical identity of the second semiconductor matrix and the desired color of electroluminescence. In some embodiments, for example, manganese activator is provided to a ZnS matrix in an amount up to about 4 atomic percent. Moreover, the specific identity and amount of co-activator incorporated into the second semiconductor matrix can be selected according to several considerations, including the identities of the activator and second semiconductor matrix as well as the desired color and efficiency of electroluminescence.

The second semiconductor matrix having activator and/or co-activator dispersed throughout can be an n-type semiconductor or a p-type semiconductor, depending on the identity of the activator and/or co-activator. For example, manganese doped ZnS can provide an n-type semiconductor matrix.

The second polycrystalline semiconductor matrix can have any thickness not inconsistent with the objectives of the present invention. The second semiconductor matrix, for example, can have a thickness selected from Table II.

Table II - Thickness of Second Polycrystalline Semiconductor Matrix

< 1 μπι

50 nm - 800 nm

100 nm - 500 nm

75 nm - 300 nm

100 nm - 200 nm

1 μπι

The first polycrystalline matrix and second polycrystalline semiconductor matrix can be deposited by any method not inconsistent with the objectives of the present invention. In some embodiments, the first polycrystalline matrix and second polycrystalline semiconductor matrix are deposited by various thin film deposition techniques including atomic layer deposition (ALD), chemical vapor deposition (CVD) or physical vapor deposition (PVD). Suitable PVD methods can include sputtering or thermal evaporation. The first polycrystalline matrix, in some embodiments, is deposited first on a suitable substrate, such as an electrode of the

electroluminescent device. The second polycrystalline semiconductor matrix is subsequently deposited over the first polycrystalline matrix. Alternatively, the second polycrystalline semiconductor matrix is deposited first, followed by deposition of the first polycrystalline matrix.

In some embodiments, the deposited first polycrystalline matrix and second

polycrystalline semiconductor matrix can be in direct contact with one another. In other embodiments, one or more intermediate layer can be positioned between the first polycrystalline matrix and second polycrystalline semiconductor matrix. In such embodiments, the intermediate layer(s) can be intrinsic semiconductor (i) to provide p-i-n architectures in the electroluminescent phase.

As described herein, atomic species are migrated in the first polycrystalline matrix by application of an electric field to the matrix. The migrating atomic species form semiconducting regions in the first polycrystalline matrix, the semiconducting regions constituents of p-n junctions formed with the second polycrystalline semiconductor matrix. The electric field can be applied to the first polycrystalline matrix prior to deposition of the second polycrystalline semiconductor matrix. Alternatively, the electric field can be applied subsequent to deposition of the second polycrystalline semiconductor matrix over the first polycrystalline matrix. The electric field is applied by positioning the electroluminescent phase between first and second electrodes. There is no requirement that the first and second electrodes are commensurate with the front and back surface areas of the electroluminescent phase. The first and second electrodes, for example, may only partially cover surfaces of the electroluminescent phase.

An alternating current (AC) voltage can be provided to the first and second electrodes to apply the electric field to the first polycrystalline matrix. Moreover, a direct current (DC) voltage can be provided to the first and second electrodes to apply the electric field to the first polycrystalline matrix. Any strength of electric field suitable for migrating atomic species in the first polycrystalline matrix for the establishment of semiconducting regions described herein can be employed. For example, electric field strength, in some embodiments, is in the range of 10³ V/m to 10⁷ V/m. Further, the electric field can be applied for any time period sufficient for semiconductor region formation. In some embodiments, the electric field is applied for a time period of 5 minutes to 5 hours. Shorter or longer electric field application times can be realized depending on several considerations including electric field strength and mobility of the migrating species in the first polycrystalline matrix. Additionally, the electric field can be applied to the first polycrystalline matrix at room temperature or elevated temperature.

The electric field, in some embodiments, is applied substantially parallel to the length of the first polycrystalline matrix. Application in a parallel direction permits migrating atomic species to move laterally or substantially laterally through the first polycrystalline matrix.

Further, substantially parallel electric field application inhibits driving migrating atomic species into the adjacent layer of second polycrystalline semiconductor matrix and promotes formation of semiconducting regions at the interface with the second polycrystalline semiconductor matrix, thereby providing p-n junctions of the electroluminescent phase. Once formed, the semiconducting regions of the first polycrystalline matrix, in some embodiments, do not migrate or substantially migrate during operation of the electroluminescent device.

Application of the electric field, in some embodiments, migrates atomic species from the first polycrystalline matrix into the adjacent second polycrystalline matrix. Migration of atomic species into the second polycrystalline semiconductor matrix can result in the formation of carrier injection structures in the second polycrystalline matrix. Migrating atomic species can aggregate or insert into the lattice and/or interstitial sites of the second polycrystalline semiconductor matrix to provide the carrier injection structures. Such carrier injection structures, in some embodiments, can form bulk p-n junctions with the second polycrystalline semiconductor matrix. For example, cationic copper, in some embodiments, can migrate into the second polycrystalline matrix of n-doped ZnS to form p-type carrier injection structures of Cu_xS wherein x is from 1.8-2.0.

First and second electrodes for application of the electric field can be independently selected from the group consisting of metals, alloys and electrically conducting radiation transmissive materials. Metals suitable for use as a first or second electrode can include aluminum, gold, copper, platinum, silver, nickel, iron or alloys thereof. Electrically conductive radiation transmissive materials, in some embodiments, are radiation transmissive conducting oxides. Radiation transmissive conducting oxides include indium tin oxide (ITO), gallium indium tin oxide (GITO), zinc indium tin oxide (ZITO), indium antimony oxide (IAO) and antimony tin oxide (ATO). First and second electrodes can have any thickness not inconsistent with the objectives of the present invention. In some embodiments, the first and second electrodes have a thickness ranging from 100 nm to 1 μιτι. EXAMPLE

An electroluminescent device was constructed as follows. A quartz substrate was provided and a first electrode was deposited on a portion of the quartz substrate. To construct the first electrode, 10 nm of chromium was initially deposited by thermal evaporation followed by 190 nm of gold by thermal evaporation. An electron beam was employed for the thermal evaporation at a pressure on the order of 10^"5 torr. A first polycrystalline matrix of Cu_xS was deposited over the first electrode and remainder of the quartz substrate by thermal evaporation of Cu₂S powder. The deposited first polycrystalline matrix of Cu_xS demonstrated a thickness of about 200 nm. A second polycrystalline semiconductor matrix of ZnS:Mn,Cl was deposited directly on the Cu_xS polycrystalline matrix by thermal co-evaporation of ZnS:Mn,Cl powder and Mn to a thickness of about 200 nm. Thermal depositions of the Cu_xS, ZnS:Mn,Cl and Mn were administered using resistive heating of the respective powders at a pressure on the order of 10^"6 mbar. The first Cu_xS polycrystalline matrix and second ZnS:Mn,Cl polycrystalline

semiconductor matrix constituted the electroluminescent phase of the device. The

electroluminescent phase was then annealed under vacuum of 10^" torr for 30 minutes at a temperature of 600°C. A gold second electrode was subsequently thermally deposited on a portion of the second ZnS:Mn,Cl polycrystalline semiconductor matrix.

A DC electric field having field strength of about 10⁵ Vm^"1 was applied to the

electroluminescent phase including the first Cu_xS polycrystalline matrix. Application of the electric field migrated cationic copper in the first polycrystalline matrix forming p-type regions of Cu_xS wherein x ranged from 1.8-2.0. The p-type regions formed p-n junctions with the n-type ZnS:Mn,Cl second polycrystalline matrix. These electroformed p-n junctions are evidenced in Figure 1. As illustrated in Figure 1 , light emission was observed from the junctions when forward biased. Current provided to the light the devices was on the order to 100 mA. Dark regions at the interface of the first polycrystalline matrix and second polycrystalline

semiconductor matrix may correspond to regions of the Cu_xS matrix lacking sufficient copper for p-type formation. In some embodiments, these dark regions have experienced copper depletion resulting from copper migration in the applied electric field.

II. Methods of Making Photovoltaic Devices

In another aspect, methods of making photovoltaic devices are described herein. A method of making a photovoltaic device comprises providing a photosensitive phase between a first electrode and second electrode, the photosensitive phase comprising a layer of first polycrystalline matrix and migrating an atomic species in the first polycrystalline matrix by application of an electric field to the first polycrystalline matrix. The migrating atomic species form semiconducting regions in the first polycrystalline matrix, the semiconducting regions constituents of p-n junction of the photosensitive phase. The first polycrystalline matrix of the photosensitive phase can be of the formula M₁X₁, wherein Mi is selected from the group consisting of metallic elements including transition metals and Xi is selected from the group consisting of non-metallic elements of Groups IVA, VA and VIA of the Periodic Table. Mi, for example, can be selected from metallic elements of Groups IB, IIB and IIIA of the Periodic Table. In some embodiments, Mi is the sole migrating atomic species under the applied electric field. In other embodiments, atomic species in addition to Mi may migrate, such as other cationic metallic atomic species and/or anionic species in the first polycrystalline matrix. Alternatively, migrating atomic species are not of the species forming the lattice of the first polycrystalline matrix. In such embodiments, migrating atomic species can comprise cationic and/or anionic dopants such as cationic metals, halides or chalcogenides.

The first polycrystalline semiconductor matrix can have any thickness not inconsistent with the objectives of the present invention. As described herein, the first polycrystalline matrix can be a light absorber for the photovoltaic device. In such embodiments, the first

polycrystalline semiconductor matrix has a thickness sufficient for the efficient absorption of electromagnetic radiation. The first polycrystalline matrix, for example, can have thickness selected from Table III.

Table III - Thickness of First Polycrystalline Matrix

< 1 μιη

50 nm - 800 nm

100 nm - 500 nm

75 nm - 300 nm

100 nm - 200 nm

> 1 μηι As a non-limiting example, the first polycrystalline matrix of the photovoltaic device can comprise Cu_xS. When the first polycrystalline matrix is formed of Cu_xS, cationic Cu can be the migrating atomic species. Under the applied electric field, cationic Cu can migrate in the polycrystalline matrix forming regions of Cu_xS having stoichiometry of p-type semiconductor. In such embodiments, p-type regions of semiconducting Cu_xS have a stoichiometry wherein x ranges from 1.8-2.

embodiments, the second polycrystalline semiconductor matrix is of the formula M₂X₂, wherein M₂ is selected from the group consisting of metallic elements including transition metals and X₂ is selected from the group consisting of non-metallic elements of Groups IV A, VA and VIA of the Periodic Table. M₂, for example, can be selected from metallic elements of Groups IB, IIB and IIIA of the Periodic Table. The second polycrystalline semiconductor matrix can be formed of transition metal oxides, transition metal chalcogenides or transition metal halides. The second polycrystalline matrix, for example, can be formed of n-type titania (Ti0₂).

The second polycrystalline semiconductor matrix can have any thickness not inconsistent with the objectives of the present invention. The second semiconductor matrix, for example, can have a thickness selected from Table IV.

Table IV - Thickness of Second Polycrystalline Semiconductor Matrix

≤ 1 μηι

50 nm - 800 nm

100 nm - 500 nm

75 nm - 300 nm

100 nm - 200 nm

≥ 1 μηι

The first polycrystalline matrix and second polycrystalline semiconductor matrix of the photovoltaic device can be deposited by any method not inconsistent with the objectives of the present invention. In some embodiments, the first polycrystalline matrix and second

polycrystalline semiconductor matrix are deposited by various thin film deposition techniques including atomic layer deposition (ALD), chemical vapor deposition (CVD) or physical vapor deposition (PVD). Suitable PVD methods can include sputtering or thermal evaporation. The first polycrystalline matrix, in some embodiments, is deposited first on a suitable substrate, such as a first electrode of the electroluminescent device. The second polycrystalline semiconductor matrix is subsequently deposited over the first polycrystalline matrix. Alternatively, the second polycrystalline semiconductor matrix is deposited first, followed by deposition of the first polycrystalline matrix. In some embodiments, the deposited first polycrystalline matrix and second polycrystalline semiconductor matrix can be in direct contact with one another. In other embodiments, one or more intermediate layers can be positioned between the first polycrystalline matrix and second polycrystalline semiconductor matrix. In such embodiments, the intermediate layer(s) can serve as buffer layers between the n-type and p-type materials. Buffer layer(s) for use in the photovoltaic device can be selected according to several considerations, including the chemical identities of the first polycrystalline matrix and second polycrystalline semiconductor matrix. As described herein, the semiconducting regions of the first polycrystalline matrix can comprise Cu_xS wherein x is from 1.8 to 2.0, and the second polycrystalline matrix is n-type Ti0₂. In this embodiment, buffer layer(s) of alumina and/or indium sulfide (In₂S3).

As described herein, atomic species are migrated in the first polycrystalline matrix by application of an electric field to the matrix. The migrating atomic species form semiconducting regions in the first polycrystalline matrix, the semiconducting regions constituents of p-n junctions formed with the second polycrystalline semiconductor matrix. The electric field can be applied to the first polycrystalline matrix prior to deposition of the second polycrystalline semiconductor matrix. Alternatively, the electric field can be applied subsequent to deposition of the second polycrystalline semiconductor matrix over the first polycrystalline matrix. The electric field is applied by positioning the photosensitive phase between first and second electrodes. There is no requirement that the first and second electrodes are commensurate with the front and back surface areas of the photosensitive phase. The first and second electrodes, for example, may only partially cover surfaces of the electroluminescent phase.

Further, substantially parallel electric field application inhibits driving migrating atomic species into the adjacent layer of second polycrystalline semiconductor matrix and promotes formation of semiconducting regions at the interface with the second polycrystalline semiconductor matrix, thereby providing p-n junctions of the electroluminescent phase. Once formed, the

semiconducting regions of the first polycrystalline matrix do not migrate during operation of the photovoltaic device.

Application of the electric field, in some embodiments, migrates atomic species from the first polycrystalline matrix into the adjacent second polycrystalline matrix. Migration of atomic species into the second polycrystalline semiconductor matrix can result in the formation of exciton pathway structures in the second polycrystalline matrix. Migrating atomic species can aggregate or insert into the lattice and/or interstitial sites of the second polycrystalline semiconductor matrix to provide the exciton pathway structures. Such exciton pathway structures, in some embodiments, can form bulk p-n junctions with the second polycrystalline semiconductor matrix. For example, cationic copper, in some embodiments, can migrate into the second polycrystalline matrix of n-type Ti0₂ to form p-type exciton pathways of Cu_xS wherein x is from 1.8-2.0.

First and second electrodes for application of the electric field can be independently selected from the group consisting of metals, alloys and electrically conducting radiation transmissive materials. Metals suitable for use as a first or second electrode can include aluminum, gold, copper, platinum, silver, nickel, iron or alloys thereof. Electrically conductive radiation transmissive materials, in some embodiments, are radiation transmissive conducting oxides. Radiation transmissive conducting oxides include indium tin oxide (ITO), gallium indium tin oxide (GITO), zinc indium tin oxide (ZITO), indium antimony oxide (IAO) and antimony tin oxide (ATO). First and second electrodes can have any thickness not inconsistent with the objectives of the present invention. In some embodiments, the first and second electrodes have a thickness ranging from 100 nm to 1 μηι. Various embodiments of the invention have been described in fulfillment of the various objectives of the invention. It should be recognized that these embodiments are merely illustrative of the principles of the present invention. Numerous modifications and adaptations thereof will be readily apparent to those skilled in the art without departing from the spirit and scope of the invention.

Claims

1. A method of making an electroluminescent device comprising:

providing an electroluminescent phase between a first electrode and a second electrode, the electroluminescent phase comprising a layer of first polycrystalhne matrix; and

migrating an atomic species in the first polycrystalhne matrix by application of an electric field to the first polycrystalhne matrix, the migrating atomic species forming semiconducting regions in the first polycrystalhne matrix, the semiconducting regions constituents of p-n junctions of the electroluminescent phase.

2. The method of claim 1 , wherein the p-n junctions are formed of the semiconducting regions of the first polycrystalhne matrix and a layer of second polycrystalhne semiconductor matrix adjacent to the first polycrystalhne matrix.

3. The method of claim 2, wherein the first polycrystalhne matrix is of the formula MjXj , and the second polycrystalhne semiconductor matrix is M₂X₂, wherein Mi and M₂ are independently selected from the group consisting of transition metals and Xj and X₂ are independently selected from the group consisting of non-metallic elements of Groups IVA, VA and VIA of the Periodic Table.

4. The method of claim 3, wherein Mi and M₂ are independently selected from metallic elements of Groups IB, IIB and IIIA of the Periodic Table.

5. The method of claim 4, wherein the migrating atomic species is Mi.

6. The method of claim 5, wherein M_\X_\ is Cu_xS, and the semiconducting regions are p- type Cu_xS wherein x ranges from 1.8 to 2.

7. The method of claim 1 , wherein the semiconducting regions are localized to grain boundaries in the first polycrystalhne matrix.

8. The method of claim 1 , wherein an AC voltage is provided to the first and second electrodes to apply the electric field to the first polycrystalline matrix.

9. The method of claim 1 , wherein a DC voltage is provided to the first and second electrodes to apply the electric field to the first polycrystalline matrix.

10. The method of claim 1, wherein strength of the applied electric field ranges from

10³ Vm^ to 10⁷ Vm^"1.

11. The method of claim 1 , wherein the layer of first polycrystalline matrix has a thickness of less than about 1 μιη.

12. The method of claim 1, wherein the electric field is applied to the first polycrystalline matrix at room temperature.

13. The method of claim 1 , wherein the electric field is applied to the first polycrystalline matrix at elevated temperature.

14. The method of claim 1 , wherein the electric field is applied for a time period of 5 minutes to 5 hours to form the semiconducting regions.

15. The method of claim 14, wherein the electric field is applied for a time period of 10 minutes to 1 hour to form the semiconducting regions.

16. The method of claim 1 , wherein the semiconducting regions do not migrate in the first polycrystalline matrix during operation of the electroluminescent device.

17. A method of making an photovoltaic device comprising:

providing an photosensitive phase between a first electrode and a second electrode, the photosensitive phase comprising a layer of first polycrystalline matrix; and migrating an atomic species in the first polycrystalline matrix by application of an electric field to the first polycrystalline matrix, the migrating atomic species forming semiconducting regions in the first polycrystalline matrix, the semiconducting regions constituents of p-n junctions of the photosensitive phase.

18. The method of claim 17, wherein the p-n junctions are formed of the semiconducting regions of the first polycrystalline matrix and a layer of second polycrystalline semiconductor matrix adjacent to the first polycrystalline matrix.

19. The method of claim 18 , wherein the first polycrystalline matrix is of the formula Mi¾, and the second polycrystalline semiconductor matrix is M₂X₂, wherein Mi and M₂ are independently selected from the group consisting of transition metals and Xi and X₂ are independently selected from the group consisting of non-metallic elements of Groups IV A, VA and VIA of the Periodic Table.

20. The method of claim 19, wherein Mi and M₂ are independently selected from metallic elements of Groups IB, IIB and IIIA of the Periodic Table.

21. The method of claim 20, wherein the migrating atomic species is Mi,

22. The method of claim 21 , wherein M_\X_\ is Cu_xS, and the semiconducting regions are p- type Cu_xS wherein x ranges from 1.8 to 2.

23. The method of claim 17, wherein the semiconducting regions are localized to grain boundaries in the first polycrystalline matrix.

24. The method of claim 17, wherein an AC voltage is provided to the first and second electrodes to apply the electric field to the first polycrystalline matrix.

25. The method of claim 17, wherein a DC voltage is provided to the first and second electrodes to apply the electric field to the first polycrystalline matrix.

26. The method of claim 17, wherein strength of the applied electric field ranges from 10³ Vm^"1 to 10⁷ Vm^"1.

27. The method of claim 17, wherein the layer of first poly crystalline matrix has a thickness of less than about 1 μπι.

28. The method of claim 17, wherein the electric field is applied to the first polycrystallme matrix at room temperature.

29. The method of claim 17, wherein the electric field is applied to the first polycrystallme matrix at elevated temperature.

30. The method of claim 17, wherein the electric field is applied for a time period of 5 minutes to 5 hours to form the semiconducting regions.

31. The method of claim 30, wherein the electric field is applied for a time period of 10 minutes to 1 hour to form the semiconducting regions.

32. The method of claim 17, wherein the semiconducting regions do not migrate in the first polycrystallme matrix during operation of the photovoltaic device.

33. The method of claim 17, wherein the semiconducting regions absorb electromagnetic radiation incident on the photosensitive phase.