CN104659137B - Full-solid photon enhanced thermionic emission device - Google Patents
Full-solid photon enhanced thermionic emission device Download PDFInfo
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- CN104659137B CN104659137B CN201410802016.4A CN201410802016A CN104659137B CN 104659137 B CN104659137 B CN 104659137B CN 201410802016 A CN201410802016 A CN 201410802016A CN 104659137 B CN104659137 B CN 104659137B
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Abstract
The invention relates to a novel photo-thermal electric composite device, belongs to the field of solar energy utilization, and discloses a full-solid photon enhanced thermionic emission device. The device comprises a transparent conductive oxide layer, a back surface filed passivation layer, a cathode absorbing layer, a high conductive high insulating semi-conductor material layer and an anode in sequence from top to bottom, wherein the back surface field passivation layer is used for reducing composition of current carriers; the cathode absorbing layer is used for absorbing sunlight; the anode is used for collecting electrons. Compared with a singular photovoltaic cell or a thermionic emission device, the device can acquire relatively high energy transformation efficiency by combining the double functions of photoproduction electrons and thermionic emission; the high conductive and high heat insulating layer is inserted between the cathode and the anode of a full-solid PETE device; compared with regular photon enhanced thermionic emission device based on vacuum clearance layers, the device is low in technological difficulty, eliminates a space charge effect, and can realize promotion of efficiency in larger space through energy level matching.
Description
Technical field
The present invention relates to a kind of photo-thermal electricity multiple device, belong to field of solar energy utilization.
Background technology
At present, in conventional photovoltaic battery device caused by absorbed layer materials band structure and solar spectrum mismatch
Energy loss accounts for the 50% of overall spectrum energy, and this partition losses energy is finally many to dissipate in the form of heat.Spectral photovoltaic
The technology such as battery, multijunction solar cell reduce this damage by the matching degree improving absorbed layer band structure and solar spectrum
Consumption.But spectral photovoltaic cell multiple batteries cost is high and device design and craft difficult it is difficult to spread.In recent years
The hot carrier battery putting forward passes through quick collection hot carrier, suppresses lattice thermal losses, can reach in theory close to many
The high efficiency of junction battery.Its advantage is that two terminal device structure is simple, and without optical electivity, but difficult point is the heat to nonequilibrium state
Carrier is collected.Hot carrier is high with the thermally equilibrated speed of lattice, and the therefore requirement to material is very high, realizes difficulty
Too big.
The sixties in 20th century thermionic energy converter (Thermionic energy converters (TECs), that is, very
Empty thermionic emission device) it is suggested and used in the automatic power supply of deep space aircraft by NASA and the former Soviet Union, its efficiency reaches
10%-15%.Inspired by this thinking, the researcher of Stanford University [Schwede, J.W., I.Bargatin,
D.C.Riley,B.E.Hardin,S.J.Rosenthal,Y.Sun,F.Schmitt,P.Pianetta,R.T.Howe,Z.-
X.Shen and N.A.Melosh, Nat.Mater., 9,762 (2010)] proposed the enhanced thermoelectron of photon in 2010 and send out
Penetrate the concept of (Photon Enhanced Thermionic Emission, PETE).PETE device is based on Vacuum Heat electron emission
Principle, using semi-conducting material as emitter stage, on the one hand passes through on the other hand pass through heat with the energy of transition absorption photon
Electron emission converts heat into electric energy.Compare traditional Vacuum Heat electron emission device, PETE absorbed layer is because absorb light
Sub- energy, light induced electron has higher fermi level, therefore improves thermionic emission probability, effectively reduces thermoelectron and sends out
The temperature penetrated, improves emission current.The quantum to photon for the device can be taken full advantage of with the combination absorbing with thermionic emission
Absorb and heat energy, therefore can reach comprehensive, relatively higher electricity conversion.Simulation calculates and finds, 1000suns's
Under the conditions of optically focused, its efficiency is up to more than 60%, considerably beyond the transformation efficiency of current solaode.Absorb and turn from effective
From the perspective of changing photon energy, PETE device and hot carrier battery [A.L.Bris, J.-F.Guillemoles,
Appl.Phys.Lett., thinking 97,113506 (2010)] is similar to.But also there is important difference between the two, hot carrier electricity
Pond is directed to nonequilibrium state carrier it is desirable to high carrier collection and the speed deriving, and is difficult on material and technology
Realize;And PETE is directed to reach " hot " carrier of thermal equilbrium state with lattice, therefore technical difficulty substantially reduces.
Improve the strategy of energy conversion efficiency in comprehensive solaode and thermionic emission device, can be from reduction negative electrode
The aspect such as work function, suppression surface carrier recombination rate, raising electric conductivity and heat stability, suppression heat loss improves light further
The energy conversion efficiency of thermoelectricity multiple device.PETE device in order to maintain the larger temperature difference between anode and cathode and remain one micro-
The vacuum space gap layer of meter Hou Du, this brings some important negative effects to the practicality of this device.First, this vacuum gap
Layer increased larger difficulty also to the preparation technology of device, needs at present to be realized by means of micro electronmechanical (MEMs) technology.Its
Secondary, vacuum space gap layer can bring space charge effect under high emission current conditions, stops the electronics of emission of cathode from reaching anode,
Reduce thermionic effective transmitting.Simulated calculating [T.Ito and M.A.Cappelli, Appl.Phys.Letts.101,
213901 (2012)] show, even if this space charge effect also can seriously reduce device under larger vacuum gap (100 μm)
The service behaviour of part.In addition, this PETE device is overly dependent upon the work function of negative electrode, anode, its physical essence determines this
Planting device is a kind of low voltage and high current device, can have larger ohmic loss.Have larger net between cathode and anode to be made
It is necessary to reduce the work function of negative electrode, coat reduction work function by cathode surface is to improve having of electron-hit emitting to emission current
One of effect means.But the low work function surface coating having now been found that (common such as alkali metal, is based on alkali-metal chemical combination
Thing) generally not high, the such as conventional Cs of temperature stability2CO3Face coat just becomes unstable at 120 DEG C about.Therefore, base
In vacuum space gap layer PETE device due to depending on the work function of cathode and anode unduly, be limited by negative electrode low work function coating relatively low
Temperature stability it is difficult to really realize the advantage of the thermionic emission under high temperature.
Content of the invention
For the problems referred to above or deficiency, the present invention proposes a kind of all solid state photon and strengthens thermionic emission device, this device
Part includes from top to bottom successively:Transparent conductive oxide (Transparent and conductive oxides, TCO) layer, uses
In back surface field (back surface field, the BSF) passivation layer reducing Carrier recombination, for absorbing the negative electrode of sunlight
Absorbed layer, high connductivity high thermal insulation semiconductor material layer and the anode for collecting emission of cathode electronics;
Described back surface field passivation layer and negative electrode absorbed layer include the height junction structure being made up of different levels of doping;
Described high connductivity high thermal insulation semiconductor material layer is " phonon glasses/electron crystal " (Phonon glass/
Electron crystal, PGEC), there is in such material crystal structure three kinds of different crystallographic site, two of which position
The atom put forms basic crystal structure, and leading band structure, and the third atom is then located at first two atomic building
Caged clearance position, and with neighboring atom weak binding, phonon is produced compared with strong scattering, thus reducing thermal conductivity.
Conduction band band rank between described negative electrode absorbed layer and the high heat insulation layer of high connductivity and the high heat insulation layer of high connductivity and anode with
Corresponding Valence-band Offsets make electronics transmit to anode and stop that hole transports to anode.
Described tco layer is p-type or N-type transparent conductive oxide film.
Described all solid state photon strengthens thermionic emission device and also includes a beam condensing unit being arranged above tco layer,
For increasing the intensity of the incident radiation inciding absorbed layer.
The present invention passes through insertion high connductivity high thermal insulation semi-conducting material " phonon glasses/electron crystal " between cathode and anode
PGEC thermoelectric material, to realize the high temperature difference of cathode and anode and the transmission of electric charge simultaneously, it is to avoid above-mentioned based on vacuum space gap layer
The drawbacks of PETE device, eliminate space charge effect, reduce device technology difficulty and the dependency to material work functions, increase
Big device efficiency room for promotion.
Brief description
Fig. 1 shows that photon strengthens the basic physical thought that thermionic emission technology utilizes photoelectricity and thermo-electric conversion simultaneously;
Fig. 2 is that the photon based on vacuum space gap layer strengthens thermionic emission device principle and band structure schematic diagram;
Fig. 3 is that the photon based on vacuum space gap layer strengthens the space charge effect schematic diagram in thermionic emission device;
Fig. 4 is the cathode construction schematic diagram with back surface field (BSF) passivation layer and low work function coating;
Fig. 5 is the structural representation that all solid state photon strengthens thermionic emission device;
Fig. 6 is a kind of level structure figure that all solid state photon strengthens thermionic emission device;
Reference:201- negative electrode absorbed layer, 202- anode, 203- photon, electronics (205)-hole (204) are right, 401-
Heavily doped BSF layer, 501- transparent conductive oxide tco layer, the high adiabatic semiconductor layer of 502- high connductivity, 601- negative electrode absorbs
Layer and high connductivity high heat insulation layer conduction band band rank, 602- negative electrode absorbed layer and high connductivity high heat insulation layer Valence-band Offsets, 603- high connductivity
High heat insulation layer and anode conduction band band rank, the high heat insulation layer of 604- high connductivity and anode Valence-band Offsets.
Specific embodiment
The present invention is to strengthen thermionic emission (PETE) principle based on photon, overcomes based on vacuum space gap layer simultaneously again
The shortcoming of PETE technology, belongs to all solid state photon and strengthens thermionic emission device, is a kind of new photo-thermal electricity multiple device.
Fig. 5 shows that all solid state photon of the present invention strengthens the structural representation of thermionic emission device.Photon (203) is from upper
Side is incident, and this device includes from top to bottom successively:Transparent conductive oxide tco layer (501), heavily doped BSF layer (401), cloudy
Pole absorbed layer (201), the high adiabatic semiconductor layer (502) of high connductivity and anode (202).Tco layer therein is p-type or N-type
Transparent conductive oxide.Back surface field passivation layer is made up of P+-GaAs/P-GaAs with the height junction structure of negative electrode absorbed layer.High
Conductive high thermal insulation semiconductor material layer had not only enabled electric charge transmission but also can keep the larger temperature difference between cathode and anode.High connductivity is high
Heat insulation layer selects substrate skutterudite (Skutterudite) material of rare earth element filling, and skutterudite is CoAs3、CoSb3Or
IrSb3, rare earth element is La or Ce, and the wherein atom of host material crystallographic site forms basic crystal structure, and leading
Band structure, and fill rare earth atom La or Ce then be located at first two atomic building caged clearance position in, and with surrounding
Atom weak binding, produces scattering to phonon, thus reducing thermal conductivity.This structure does not have vacuum space gap layer, reduces based on vacuum
The manufacturing process difficulty of clearance layer PETE device, eliminates the negative effect to device performance for the space charge effect.
Fig. 6 is a kind of band structure figure that all solid state photon strengthens thermionic emission device.Photon (203) enters negative electrode and inhales
Receive layer (201), through photon energy absorption, produce electronics (205)-hole (204) in negative electrode semi-conducting material right.High connductivity is high
Between heat insulation layer (502) insertion negative electrode absorbed layer (201) and anode (202), because this layer of thermal conductivity is very low, can keep cloudy
The larger temperature difference between pole, anode.The high heat insulation layer of negative electrode, high connductivity and anode are all semi-conducting materials, can be adjusted by doping
Save respective band structure and level-density parameter between them, as shown in FIG., negative electrode absorbed layer (201) and the high heat insulation layer of high connductivity
(502) conduction band band rank (601) is less than corresponding Valence-band Offsets (602) to realize the selectivity transmission to electronics.Made by doping
Conduction band band rank (603) obtaining between the high heat insulation layer of high connductivity and anode makes electronics pass to anode with corresponding Valence-band Offsets (604)
Defeated and stop hole to anode transmit.
Fig. 4 shows the cathode construction of back surface field passivation layer (BSF) and low work function coating.Comprehensive solaode with
Improve the strategy of energy conversion efficiency, the combination of negative electrode BSF and low work function coating can be dropped simultaneously in thermionic emission device
The surface recombination loss of low photo-generated carrier and emission of cathode potential barrier layer height.Incident photon (203) passes through heavily doped P+Layer
(401) absorbed layer (201), wherein P are entered+Layer plays back surface field passivation, is passivated by field and reduces carrier in back of the body table
The recombination losses in face, the face coat (402) of negative electrode absorbed layer in order to reduce cathode material work function, thus strengthening negative electrode thermoelectricity
Sub- emission probability.
Fig. 1 shows that PETE realizes the basic physical thought of photoelectricity and thermo-electric conversion simultaneously.Conventional solaode has
Two big heat loss approach, photon energy h ν is more than solaode band gap EgPart h ν-EgSound can be passed to by relaxation process
Son and dissipate;And energy is less than EgPhoton also by because do not dissipated in the form of heat by absorption.In crystalline silicon electricity
Chi Zhong, both accounts for the 50% of sunlight incidence gross energy.And the thermionic energy conversion dress based on thermionic emission principle
Put (thermionic energy converters, TECs) and the heat that in solaode, this partial loss is fallen can be made full use of
Energy.Richard's-Du Shiman formula[G.N.Hatsopoulos and E.P.Gyftopoulos,
Thermionic Energy Conversion Vol.1 (MIT Press, 1973)] describe heat emission current density, J and temperature
Degree TCAnd cathode material work function φCBetween relation, wherein ACIt is Richard's coefficient of cathode material.PETE device is exactly tied
Close the thermionic emission process of the quantums absorption in conventional solaode and TECs device, so there is higher energy turning
Change efficiency.
Fig. 2 gives principle and the band structure schematic diagram of the PETE device based on vacuum space gap layer.Device cathodes absorb
Layer 201 and anode 202 pass through vacuum insulation, and negative electrode absorbed layer 201 and anode 202 are respectively provided with respect to vacuum level φVery's
Work function φCAnd φA.Cathode material band gap width is Eg, before illumination, fermi level position is in EF, electronics occupies number as curves 206
Shown;After illumination, quasi-Fermi level position is in EF,n, electronics occupy number as shown in curve 207.Incident photon (203) incides the moon
During pole, Electron absorption photon energy, transit to conduction band from valence band, produce electronics (205) hole (204) right.The electricity being excited
Son, in negative electrode conduction band rapid thermalization, reaches new thermal equilibrium state.Electrons spread reaches cathode surface, overcomes surface affinity χ
Occur heat emission to pass through vacuum area (208) to reach anode, form thermal electron stream (209)Compare the situation not having illumination, the potential barrier of electron-hit emitting reduces EF,n-EF, the fall of potential barrier
The low just corresponding difference with illumination quasi-Fermi level and the fermi level of no light.That is, illumination effect is significantly dropped
The threshold temperature of the internal thermionic emission of low quasiconductor.Generally thermionic temperature is in more than 1100K, and PETE can lead to
Cross threshold temperature that photonic absorption occurs thermoelectron and drop to 500K.
Fig. 3 is that the photon based on vacuum space gap layer strengthens the space charge effect schematic diagram in thermionic emission.Incident illumination
It is right, because launching electronics reach from emission of cathode that sub (203) produce electronics (205) hole (204) in negative electrode absorbed layer (201)
Anode (202) needs the regular hour, causes electronics to form 301 vacuum gap Potential Distributing in the accumulation of vacuum layer, electricity
Son is launched it is necessary to overcome the potential barrier between 302 to 303 to get to anode surface (304), 303 are from cathode surface (302)
Vacuum layer potential peak.Therefore the electric charge accumulation effect of vacuum layer can substantially reduce the efficiency of thermionic emission.
Claims (4)
1. a kind of all solid state photon strengthens thermionic emission device, includes successively from top to bottom:Including transparent conducting oxide layer, is used for
Reduce the back surface field passivation layer of Carrier recombination, for absorbing the negative electrode absorbed layer of sunlight, high connductivity high thermal insulation quasiconductor
Material layer and for collect emission of cathode electronics anode it is characterised in that:
Described back surface field passivation layer and negative electrode absorbed layer include the height junction structure being made up of different levels of doping;
Described high connductivity high thermal insulation semiconductor material layer is " phonon glasses/electron crystal ", has in such material crystal structure
Three kinds of different crystallographic site, the atom of two of which position forms basic crystal structure, and leading band structure, and the
Three kinds of atoms are then located at the caged clearance position of first two atomic building, and with neighboring atom weak binding;
Conduction band band rank between described negative electrode absorbed layer heat insulation layer high with high connductivity and the high heat insulation layer of high connductivity and anode with corresponding
Valence-band Offsets make electronics to anode transmit and stop that hole transports to anode;
Described height junction structure is by P+- GaAs/P-GaAs is constituted.
2. as claimed in claim 1 all solid state photon strengthen thermionic emission device it is characterised in that:Described transparent conductive oxide
Nitride layer is p-type or N-type transparent conductive oxide film.
3. described all solid state photon as arbitrary in claim 1-2 strengthen thermionic emission device it is characterised in that:Described high connductivity
High heat insulation layer selects the substrate skutterudite material of rare earth element filling, and rare earth element is at least one in La and Ce, skutterudite
Material is CoAs3、CoSb3Or IrSb3.
4. as claimed in claim 1 all solid state photon strengthen thermionic emission device it is characterised in that:Also include one to be arranged at
Beam condensing unit above including transparent conducting oxide layer.
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ES2584105B2 (en) * | 2016-02-04 | 2017-07-24 | Universidad Politécnica de Madrid | Hybrid thermionic-photovoltaic converter |
JP6311133B2 (en) * | 2016-06-13 | 2018-04-18 | パナソニックIpマネジメント株式会社 | Infrared sensor |
CN106571763A (en) * | 2016-10-25 | 2017-04-19 | 中国电子科技集团公司第十八研究所 | PETE-thermoelectric composite power generation system |
CA3067633A1 (en) * | 2017-06-05 | 2018-12-13 | Florian METZLER | System and method for generating photon emission from atomic nuclei |
CN108615781A (en) * | 2018-03-20 | 2018-10-02 | 南京合智电力科技有限公司 | A kind of novel electron ballistic device |
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