WO1995028008A1 - Solid-state solar cell - Google Patents

Solid-state solar cell Download PDF

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Publication number
WO1995028008A1
WO1995028008A1 PCT/DE1995/000485 DE9500485W WO9528008A1 WO 1995028008 A1 WO1995028008 A1 WO 1995028008A1 DE 9500485 W DE9500485 W DE 9500485W WO 9528008 A1 WO9528008 A1 WO 9528008A1
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Prior art keywords
layer
solid
solar cell
state solar
cell according
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PCT/DE1995/000485
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German (de)
French (fr)
Inventor
Manfred Brauer
Manfred Schmidt
Klaus Ellmer
Frank Fenske
Hans Flietner
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Hahn-Meitner-Institut Berlin Gmbh
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Priority to AU22536/95A priority Critical patent/AU2253695A/en
Publication of WO1995028008A1 publication Critical patent/WO1995028008A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
    • H01L31/06—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by potential barriers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
    • H01L31/06—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by potential barriers
    • H01L31/062—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by potential barriers the potential barriers being only of the metal-insulator-semiconductor type
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy

Definitions

  • the invention relates to a solid-state solar cell.
  • a defined arrangement of layers causes the generation and transport of charge carriers in a semiconducting layer for the purpose of energy conversion from optical to electrical energy.
  • the energy conversion from optical to electrical energy can be carried out both with photoelectrochemical solar cells and with solid-state solar cells, in these e.g. using p / n transition, Schottky contact or inversion edge layer.
  • a photoelectrochemical solar cell (DE-Al 42 07 659), which represents a semiconductor / electrolyte contact and in which a chromophore is arranged on the light-incident side of this layer on a thin semiconductor layer
  • electrons are caused by the incident light in the dye generated, given to the semiconducting material, charge carriers subsequently supplied and drawn off over a glass provided with a conductive layer.
  • this photoelectrochemical cell uses less incident light than conventional silicon cells.
  • the same photoelectrochemical titanium dioxide cell uses the photon range twice as well as a conventional photo cell.
  • a Schottky contact or an inversion edge layer on the side of the corresponding layer system facing the incident light there are one or more antireflection layers in such a thickness that as much as possible more than 95% of the incident light get into the area of the solar cell, namely in the Semiconductor layer in which free charge carriers are then generated and separated by the electrical field and by diffusion. All arrangements of this type have in common that the optical excitation and the transport of the charge carriers take place in the same solid body and thus an independent optimization of absorption and transport properties is not possible.
  • the light can only be used up to photon energies that correspond to the gap energy of the semiconductor used (typically: 1 eV to 1.5 eV).
  • the invention is based on the technical problem of creating a solar cell which both uses their respective advantages and avoids their respective disadvantages of photoelectrochemical and solid-state solar cells.
  • a solid-state solar cell is designed as a photo-injection cell and is made up of a layer sequence in which a low-resistance collector layer with a thickness of 100 nm to 1000 nm and a work function of 2 eV to 4 eV has a 50 nm to above it 1000 nm thick and an energy gap of 2 eV to 4 eV having a quasi-insulating charge transfer layer and a superabsorbent, a thickness of 5 nm to 100 nm, preferably 5 nm to 50 nm, and a work function of 3 eV to 5 eV having a work function.
  • the optical excitation and the transport of the charge carriers take place separately in the different solid layers.
  • the work function differences between the photoemitter and collector layers, the quantum yield of photoinjection from the photoemitter layer, the energy gap of the charge transfer layer and the thicknesses of these three layers are decisive for the functions which run separately in the solid-state solar cell according to the invention.
  • the isotropic quasi-oriental scattering rates in the photoemitter layer are greater than that Scattering rates of the inelastic scattering processes and the thickness of the photoemitter layer have the same order of magnitude as that of the free path length of the inelastic scattering processes.
  • the charge carriers are transported through the impressed field, caused by the work function difference of the two layers adjacent to them ⁇ 2.5 eV, or / and by diffusion to the collector layer.
  • the photoinjection cell according to the invention supplies an open circuit voltage which is less than or equal to the work function difference of the photoemitter and collector layers and is not limited by the energy gap of the charge transfer layer.
  • the open circuit voltage can be greater than the diffusion voltage of a conventional Si solar cell.
  • the short-circuit current is essentially determined by the quantum efficiency of the photoemitter layer.
  • the charge transfer layer is formed from a wide-gap semiconductor or an insulator.
  • the highly absorbing photoemitter layer is formed from a semiconductor or a metal.
  • the surface of the side of the charge transfer layer facing the photoemitter is porous or nanocrystalline. This design causes the effective surface to be enlarged many times over compared to the geometric surface, and thus improves efficiency.
  • the photoemitter layer faces the incident light, and the exposure takes place from the front.
  • the substrate faces the incident light, and the solid-state solar cell is exposed from the rear.
  • the collector layer is formed from an optically transparent semiconductor, for example: ITO.
  • the substrate is a glass substrate.
  • an antireflection layer on the layer of the layer sequence facing the incident light.
  • the layer system according to the invention for a solid-state solar cell can advantageously be produced using known thin-film techniques.
  • the technical teaching according to the invention enables the use of the solar spectrum from 0.5 eV with a photo injection cell, consisting of a layer system with photo emitter, charge transfer and collector layers.
  • the functions of the individual layers, especially the photoemitter layer and the charge transfer layer can be optimized separately with regard to absorption and transport properties. This means that new materials can be used that no longer have to meet extreme semiconductor requirements.
  • the layer system can be produced over a large area by means of known thin-layer techniques, so that the cost per watt of electrical power can be drastically reduced.
  • the solid-state solar cell according to the invention enables easier handling during operation than a photoelectrochemical solar cell.
  • Fig. 2 the corresponding band scheme.
  • the photo injection cell shown in Fig. 1 consists of a layer sequence with a 15 nm thick photoemitter layer 1 made of Au, which has effective free path lengths ⁇ 500 ⁇ , a 100 nm thick charge transfer layer 2 made of ZnO and a collector layer 3, which is 100 nm thick and is from Gd.
  • This layer structure is arranged on a glass substrate 4.
  • the band diagram shown in FIG. 2 arises from the different work functions ⁇ M 1) and ⁇ M ⁇ 2 > of the two layers 1 (Au) and 3 (Gd) described in FIG. 1.
  • the light incident on the photoemitter layer 1 causes the generation of charge carriers in this layer.
  • the charge carriers must overcome a barrier, the size of which results from the position of the Fermini level E F of the Au photoemitter layer 1 relative to the conduction band edge E c of the ZnO charge transfer layer 2, and are injected into the charge transfer layer 2.
  • the charge carriers are transported into the Gd collector layer 3 by the electrical field caused by the different work functions ⁇ M ( ' ) and ⁇ M () and by diffusion.

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  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • Electromagnetism (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Power Engineering (AREA)
  • Photovoltaic Devices (AREA)

Abstract

The solid-state solar cell proposed is designed as a photo-injection cell and made up of a series of layers comprising a substrate on which is located a 100 to 1000 nm thick low-impedance collector layer with an electron affinity of 2 to 4 eV, followed by a 50 to 1000 nm thick quasi-insulating charge-transfer layer with anenergy gap of 2 to 4 eV and finally a high-absorbing photo-emitter layer 5 to 100 nm, preferably 5 to 50 nm, thick with an electron affinity of 3 to 5 eV. The photo-injection cell permits separate optimization of the individual layers as regards their functions of optical excitation and charge-carrier transport in the conversion of optical energy into electrical energy.

Description

Beschreibungdescription
FestkörpersolarzelleSolid state solar cell
Die Erfindung bezieht sich auf eine Festkörpersolarzelle. Dort bewirkt eine definierte Anordnung von Schichten die Generation und den Transport von Ladungsträgern in einer halbleitenden Schicht zum Zwecke der Energiekonversion von optischer in elektrische Energie.The invention relates to a solid-state solar cell. There, a defined arrangement of layers causes the generation and transport of charge carriers in a semiconducting layer for the purpose of energy conversion from optical to electrical energy.
Die Energiekonversion von optischer in elektrische Energie läßt sich sowohl mit photoelektrochemischen Solarzellen als auch mit Festkörpersolarzellen, in diesen z.B. mittels p/n-Übergang, Schottky-Kontakt oder Inversionsrandschicht, realisieren.The energy conversion from optical to electrical energy can be carried out both with photoelectrochemical solar cells and with solid-state solar cells, in these e.g. using p / n transition, Schottky contact or inversion edge layer.
So werden in einer photoelektrochemischen Solarzelle (DE-Al 42 07 659), die einen Halbleiter/Elektrolyt-Kontakt darstellt und bei der auf einer dünn ausgebildeten Halbleiterschicht auf der lichteinfallenden Seite dieser Schicht ein Chromophor angeordnet ist, durch das einfallende Licht in dem Farbstoff Elektronen erzeugt, an das halbleitende Material abgegeben, Ladungsträger nachgeliefert und über ein mit einer leitfähigen Schicht versehenes Glas abgezogen. In direktem Sonnenlicht verwertet diese photoelektrochemische Zelle weniger einfallendes Licht als konventionelle Siliziumzellen. Doch bei diffusem Licht nutzt eine gleiche photoelektrochemische Titandioxid-Zelle das Photonenangebot doppelt so gut aus wie eine herkömmliche Photozelle. Zwar sollen die Herstellungskosten wesentlich unter denen für herkömmliche Solarzellen liegen, jedoch gibt es noch technologische Schwierigkeiten bei der Herstellung großflächiger photoelektrochemischer Solarzellen.Thus, in a photoelectrochemical solar cell (DE-Al 42 07 659), which represents a semiconductor / electrolyte contact and in which a chromophore is arranged on the light-incident side of this layer on a thin semiconductor layer, electrons are caused by the incident light in the dye generated, given to the semiconducting material, charge carriers subsequently supplied and drawn off over a glass provided with a conductive layer. In direct sunlight, this photoelectrochemical cell uses less incident light than conventional silicon cells. But in diffuse light, the same photoelectrochemical titanium dioxide cell uses the photon range twice as well as a conventional photo cell. Although the production costs are said to be significantly lower than for conventional solar cells, there are still technological difficulties in the production of large-area photoelectrochemical solar cells.
Bei konventionellen Festkörpersolarzellen auf der Grundlage eines p/n-Übergangs, eines Schottky-Kontakts oder einer Inversionsrandschicht befinden sich auf der dem einfallenden Licht zugewandten Seite des entsprechenden Schichtsystems eine oder mehrere Antireflexionsschichten in einer solchen Dicke, daß möglichst mehr als 95% des einfallenden Lichtes in den Bereich der Solarzelle gelangen, nämlich in die Halbleiterschicht, in der dann freie Ladungsträger generiert und durch das elektrische Feld und durch Diffusion getrennt werden. Allen Anordnungen dieser Art ist gemeinsam, daß die optische Anregung und der Transport der Ladungsträger im selben Festkörper stattfinden und damit eine unabhängige Optimierung von Absorption und Transporteigenschaften nicht möglich ist. Außerdem kann das Licht nur bis zu Photonenenergien, die der Gapenergie des verwendeten Halbleiters entsprechen, ausgenutzt werden (typisch: 1 eV bis 1,5 eV).In conventional solid-state solar cells based on a p / n junction, a Schottky contact or an inversion edge layer, on the side of the corresponding layer system facing the incident light there are one or more antireflection layers in such a thickness that as much as possible more than 95% of the incident light get into the area of the solar cell, namely in the Semiconductor layer in which free charge carriers are then generated and separated by the electrical field and by diffusion. All arrangements of this type have in common that the optical excitation and the transport of the charge carriers take place in the same solid body and thus an independent optimization of absorption and transport properties is not possible. In addition, the light can only be used up to photon energies that correspond to the gap energy of the semiconductor used (typically: 1 eV to 1.5 eV).
Der Erfindung liegt das technische Problem zugrunde, eine Solarzelle zu schaffen, die von photoelektrochemischen und von Festkörpersolarzellen sowohl deren jeweilige Vorzüge nutzt als auch deren jeweilige Nachteile vermeidet.The invention is based on the technical problem of creating a solar cell which both uses their respective advantages and avoids their respective disadvantages of photoelectrochemical and solid-state solar cells.
Die erfindungsgemäße Lösung sieht vor, daß eine Festkörpersolarzelle als Photoinjektionszelle ausgebildet und aus einer Schichtenfolge aufgebaut ist, bei der auf einem Substrat eine 100 nm bis 1000 nm dicke und eine Austrittsarbeit von 2 eV bis 4 eV aufweisende niederohmige Kollektorschicht, über dieser eine 50 nm bis 1000 nm dicke und eine Energielücke von 2 eV bis 4 eV aufweisende quasiisolierende Ladungstransferschicht und darauf eine hochabsorbierende, eine Dicke von 5 nm bis 100 nm, vorzugsweise 5 nm bis 50 nm, und eine Austrittsarbeit von 3 eV bis 5 eV aufweisende Photoemitterschicht angeordnet sind.The solution according to the invention provides that a solid-state solar cell is designed as a photo-injection cell and is made up of a layer sequence in which a low-resistance collector layer with a thickness of 100 nm to 1000 nm and a work function of 2 eV to 4 eV has a 50 nm to above it 1000 nm thick and an energy gap of 2 eV to 4 eV having a quasi-insulating charge transfer layer and a superabsorbent, a thickness of 5 nm to 100 nm, preferably 5 nm to 50 nm, and a work function of 3 eV to 5 eV having a work function.
In der erfindungsgemäßen Photoinjektionszelle erfolgen die optische Anregung und der Transport der Ladungsträger getrennt in den verschiedenen Festkörperschichten. Bestimmend für die getrennt ablaufenden Funktionen in der erfindungsgemäßen Festkörpersolarzelle sind die Austrittsarbeitsdifferenzen zwischen Photoemitter- und Kollektorschicht, die Quantenausbeute der Photoinjektion aus der Photoemitterschicht, die Energielücke der Ladungstransferschicht und die Dicken dieser drei Schichten.In the photoinjection cell according to the invention, the optical excitation and the transport of the charge carriers take place separately in the different solid layers. The work function differences between the photoemitter and collector layers, the quantum yield of photoinjection from the photoemitter layer, the energy gap of the charge transfer layer and the thicknesses of these three layers are decisive for the functions which run separately in the solid-state solar cell according to the invention.
Mittels Lichtabsorption werden in der Photoemitterschicht Ladungsträger erzeugt, von denen ein Teil, bestimmt durch deren Impulsverteilung, die Barriere zur Ladungstransferschicht < 1 eV überwindet. Die Quantenausbeute erhöht sich entsprechend dem Verhältnis von Photoemitterschichtdicke zu freier Weglänge für die in der Photoemitterschicht ablaufenden quasielastischen isotropen Streuprozesse drastisch.By means of light absorption, charge carriers are generated in the photoemitter layer, a part of which, determined by their momentum distribution, overcomes the barrier to the charge transfer layer <1 eV. The quantum yield increases drastically in accordance with the ratio of the photoemitter layer thickness to the free path length for the quasi-elastic isotropic scattering processes taking place in the photoemitter layer.
Deshalb ist in einer erfindungsgemäßen Ausführungsform vorgesehen, daß in der Photoemitterschicht die isotropen quasieleastischen Streuraten größer sind als die Streuraten der inelastischen Streuprozesse und die Dicke der Photoemitterschicht die gleiche Größenordnung wie die der freien Weglänge der inelastischen Streuprozesse aufweist.It is therefore provided in an embodiment according to the invention that the isotropic quasi-oriental scattering rates in the photoemitter layer are greater than that Scattering rates of the inelastic scattering processes and the thickness of the photoemitter layer have the same order of magnitude as that of the free path length of the inelastic scattering processes.
In der Ladungstransferschicht werden die Ladungsträger durch das eingeprägte Feld, verursacht durch die Austrittsarbeitsdifferenz der beiden ihr benachbarten Schichten < 2,5 eV, oder/und durch Diffusion zur Kollektorschicht transportiert.In the charge transfer layer, the charge carriers are transported through the impressed field, caused by the work function difference of the two layers adjacent to them <2.5 eV, or / and by diffusion to the collector layer.
Die erfindungsgemäße Photoinjektionszelle liefert eine Leerlaufspannung, die kleiner oder gleich der Austrittsarbeitsdifferenz der Photoemitter- und Kollektorschicht ist und nicht durch die Energleiücke der Ladungstransferschicht begrenzt wird. Die Leerlaufspannung kann bei der erfindungsgemäßen Lösung größer als die Diffusionsspannung einer konventionellen Si-Solarzelle sein. Der Kurzschlußstrom wird wesentlich durch die Quantenausbeute der Photoemitterschicht bestimmt.The photoinjection cell according to the invention supplies an open circuit voltage which is less than or equal to the work function difference of the photoemitter and collector layers and is not limited by the energy gap of the charge transfer layer. In the solution according to the invention, the open circuit voltage can be greater than the diffusion voltage of a conventional Si solar cell. The short-circuit current is essentially determined by the quantum efficiency of the photoemitter layer.
In einer erfindungsgemäßen Ausführungsform ist die Ladungstransferschicht aus einem breitlückigen Halbleiter oder einem Isolator gebildet.In one embodiment according to the invention, the charge transfer layer is formed from a wide-gap semiconductor or an insulator.
Eine weitere Ausfuhrungsform sieht vor, daß die hochabsorbierende Photoemitterschicht aus einem Halbleiter oder einem Metall gebildet ist.Another embodiment provides that the highly absorbing photoemitter layer is formed from a semiconductor or a metal.
In einer anderen Ausführungsform ist die Oberfläche der dem Photoemitter zugewandten Seite der Ladungstransferschicht porös bzw. nanokristallin ausgebildet. Diese Ausbildung bewirkt eine Vergrößerung der effektiven Oberfläche im Vergleich zur geometrischen Oberfläche um ein Vielfaches und damit eine Verbesserung der Effizienz.In another embodiment, the surface of the side of the charge transfer layer facing the photoemitter is porous or nanocrystalline. This design causes the effective surface to be enlarged many times over compared to the geometric surface, and thus improves efficiency.
In einer erfindungsgemäßen Ausführungsform ist die Photoemitterschicht dem einfallenden Licht zugewandt, die Belichtung erfolgt von der Vorderseite.In an embodiment according to the invention, the photoemitter layer faces the incident light, and the exposure takes place from the front.
In einer anderen erfindungsgemäßen Ausführungsform ist das Substrat dem einfallenden Licht zugewandt, die Belichtung der Festkörpersolarzelle erfolgt von der Rückseite.In another embodiment according to the invention, the substrate faces the incident light, and the solid-state solar cell is exposed from the rear.
Die getrennt ablaufenden Funktionen der Generation und des Transports der Ladungsträger in der erfindungsgemäßen Festkörpersolarzelle sind unabhängig von der Richtung des einfallenden Lichts. Ist das Substrat dem einfallenden Licht zugewandt, so ist die Kollektorschicht aus einem optisch transparenten Halbleiter, z.B: ITO, gebildet. Das Substrat ist in dieser Ausführungsform ein Glassubstrat.The separate functions of generation and transport of the charge carriers in the solid-state solar cell according to the invention are independent of the direction of the incident light. If the substrate faces the incident light, the collector layer is formed from an optically transparent semiconductor, for example: ITO. In this embodiment, the substrate is a glass substrate.
Als vorteilhaft hat sich zur weiteren Verbesserung der Ausnutzung des einfallenden Lichts ergeben, auf der dem einfallenden Licht zugewandten Schicht der Schichtenfolge eine Antireflexionsschicht anzuordnen.To further improve the utilization of the incident light, it has been found to be advantageous to arrange an antireflection layer on the layer of the layer sequence facing the incident light.
Das erfindungsgemäße Schichtsystem für eine Festkörpersolarzelle ist in einer weiteren Ausfuhrungsform vorteilhaft mit bekannten Dünnschichttechniken herstellbar.In another embodiment, the layer system according to the invention for a solid-state solar cell can advantageously be produced using known thin-film techniques.
Die erfindungsgemäße technische Lehre ermöglicht mit einer Photoinjektionszelle, bestehend aus einem Schichtsystem mit Photoemitter-, Ladungstransfer- und Kollektorschicht, die Ausnutzung des Solarspektrums ab 0,5 eV. Außerdem lassen sich die einzelnen Schichten, vor allem die Photoemitterschicht und die Ladungstransferschicht, in ihren Funktionen bezüglich Absorption und Transporteigenschaften getrennt optimieren. Damit sind neue Materialien einsetzbar, an die keine extremen Halbleiteranforderungen mehr gestellt werden müssen. Das Schichtsystem ist mittels bekannter Dünnschichttechniken großflächig herstellbar, so daß die Kosten je Watt elektrischer Leistung drastisch reduziert werden können. Weiterhin ermöglicht die erfindungsgemäße Festkörpersolarzelle eine einfachere Handhabung beim Betrieb als eine photoelektrochemische Solarzelle.The technical teaching according to the invention enables the use of the solar spectrum from 0.5 eV with a photo injection cell, consisting of a layer system with photo emitter, charge transfer and collector layers. In addition, the functions of the individual layers, especially the photoemitter layer and the charge transfer layer, can be optimized separately with regard to absorption and transport properties. This means that new materials can be used that no longer have to meet extreme semiconductor requirements. The layer system can be produced over a large area by means of known thin-layer techniques, so that the cost per watt of electrical power can be drastically reduced. Furthermore, the solid-state solar cell according to the invention enables easier handling during operation than a photoelectrochemical solar cell.
Eine Ausfiihrungsform der Erfindung und ihre Funktionsweise werden anhand von Zeichnungen näher erläutert. Dabei zeigenAn embodiment of the invention and its mode of operation are explained in more detail with reference to drawings. Show
Fig. 1 : den schematischen Schichtaufbau einer erfindungsgemäßen Festkörpersolarzelle,1: the schematic layer structure of a solid-state solar cell according to the invention,
Fig. 2: das entsprechende Bänderschema.Fig. 2: the corresponding band scheme.
Die in Fig. 1 dargestellte Photoinjektionszelle besteht aus einer Schichtenfolge mit einer 15 nm dicken Photoemitterschicht 1 aus Au, die effektive freie Weglängen < 500 Ä aufweist, einer darauf angeordneten 100 nm dicken Ladungstransferschicht 2 aus ZnO und einer Kollektorschicht 3, die 100 nm dick und aus Gd ist. Diese Schichtstruktur ist auf einem Glassubstrat 4 angeordnet. Das in Fig. 2 dargestellte Bänderschema entsteht durch die unterschiedlichen Austrittsarbeiten ΦM 1) und ΦM <2> der beiden in Fig. 1 beschriebenen Schichten 1 (Au) und 3 (Gd).The photo injection cell shown in Fig. 1 consists of a layer sequence with a 15 nm thick photoemitter layer 1 made of Au, which has effective free path lengths <500 Å, a 100 nm thick charge transfer layer 2 made of ZnO and a collector layer 3, which is 100 nm thick and is from Gd. This layer structure is arranged on a glass substrate 4. The band diagram shown in FIG. 2 arises from the different work functions Φ M 1) and Φ M < 2 > of the two layers 1 (Au) and 3 (Gd) described in FIG. 1.
Das auf die Photoemitterschicht 1 einfallende Licht bewirkt die Generation von Ladungsträgern in dieser Schicht. Die Ladungsträger müssen eine Barriere überwinden, deren Größe sich aus der Lage des Ferminiveaus EF der Au-Photoemitterschicht 1 relativ zur Leitungsbandkante Ec der ZnO-Ladungstransferschicht 2 ergibt, und werden in die Ladungstransferschicht 2 injiziert. Hier werden die Ladungsträger durch das von den unterschiedlichen Austrittsarbeiten ΦM (') und ΦM ( ) bewirkte elektrische Feld und durch Diffusion in die Gd-Kollektorschicht 3 transportiert. The light incident on the photoemitter layer 1 causes the generation of charge carriers in this layer. The charge carriers must overcome a barrier, the size of which results from the position of the Fermini level E F of the Au photoemitter layer 1 relative to the conduction band edge E c of the ZnO charge transfer layer 2, and are injected into the charge transfer layer 2. Here the charge carriers are transported into the Gd collector layer 3 by the electrical field caused by the different work functions Φ M ( ' ) and Φ M () and by diffusion.

Claims

Patentansprüche Claims
1. Festkörpersolarzelle, die als Photoinjektionszelle ausgebildet und aus einer Schichtenfolge aufgebaut ist, bei der auf einem Substrat eine 100 nm bis 1000 nm dicke und eine Austrittsarbeit von 2 eV bis 4 eV aufweisende niederohmige Kollektorschicht, über dieser eine 50 nm bis 1000 nm dicke und eine Energielücke von 2 eV bis 4 eV aufweisende quasiisolierende Ladungstransferschicht und darauf eine hochabsorbierende, eine Dicke von 5 nm bis 100 nm, vorzugsweise 5 nm bis 50 nm, und eine Austrittsarbeit von 3 eV bis 5 eV aufweisende Photoemitterschicht angeordnet sind.1.Solid-state solar cell, which is designed as a photo-injection cell and is constructed from a layer sequence in which a low-resistance collector layer has a thickness of 100 nm to 1000 nm and a work function of 2 eV to 4 eV, a 50 nm to 1000 nm thickness and a quasi-insulating charge transfer layer having an energy gap of 2 eV to 4 eV and a superabsorbent layer having a thickness of 5 nm to 100 nm, preferably 5 nm to 50 nm and a work function of 3 eV to 5 eV having a work function are arranged.
2. Festkörpersolarzelle nach Anspruch 1, dadurch gekennzeichnet, daß in der Photoemitterschicht die isotropen quasieleastischen Streuraten größer sind als die Streuraten der inelastischen Streuprozesse und die Dicke der Photoemitterschicht die gleiche Größenordnung wie die der freien Weglänge der inelastischen Streuprozesse aufweist.2. Solid-state solar cell according to claim 1, characterized in that in the photoemitter layer the isotropic quasi-oriental scattering rates are greater than the scattering rates of the inelastic scattering processes and the thickness of the photoemitter layer has the same order of magnitude as that of the free path length of the inelastic scattering processes.
3. Festkörpersolarzelle nach Anspruch 1, dadurch gekennzeichnet, daß die Ladungstransferschicht aus einem breitlückigen Halbleiter gebildet ist.3. Solid-state solar cell according to claim 1, characterized in that the charge transfer layer is formed from a wide-gap semiconductor.
4. Festkörpersolarzelle nach Anspruch 1, dadurch gekennzeichnet, daß die Ladungstransferschicht aus einem Isolator gebildet ist.4. Solid-state solar cell according to claim 1, characterized in that the charge transfer layer is formed from an insulator.
5. Festkörpersolarzelle nach Anspruch 1, dadurch gekennzeichnet, daß die Photoemitterschicht aus einem Metall gebildet ist.5. Solid-state solar cell according to claim 1, characterized in that the photoemitter layer is formed from a metal.
6. Festkörpersolarzelle nach Anspruch 1, dadurch gekennzeichnet, daß die Photoemitterschicht aus einem Halbleiter gebildet ist. 6. Solid-state solar cell according to claim 1, characterized in that the photoemitter layer is formed from a semiconductor.
7. Festkörpersolarzelle nach Anspruch 1, dadurch gekennzeichnet, daß die Oberfläche der dem Photoemitter zugewandten Seite der Ladungstransferschicht porös ausgebildet ist.7. Solid-state solar cell according to claim 1, characterized in that the surface of the side of the charge transfer layer facing the photoemitter is porous.
8. Festkörpersolarzelle nach Anspruch 1, dadurch gekennzeichnet, daß die Oberfläche der dem Photoemitter zugewandten Seite der Ladungstransferschicht nanokristallin ausgebildet ist.8. Solid-state solar cell according to claim 1, characterized in that the surface of the side facing the photoemitter of the charge transfer layer is nanocrystalline.
9. Festkörpersolarzelle nach Anspruch 1, dadurch gekennzeichnet, daß die Photoemitterschicht dem einfallenden Licht zugewandt ist.9. Solid-state solar cell according to claim 1, characterized in that the photoemitter layer faces the incident light.
10. Festkörpersolarzelle nach Anspruch 1, dadurch gekennzeichnet, daß das Substrat dem einfallenden Licht zugewandt ist.10. Solid-state solar cell according to claim 1, characterized in that the substrate faces the incident light.
11. Festkörpersolarzelle nach Anspruch 9, dadurch gekennzeichnet, daß die Kollektorschicht aus einem optisch transparenten Halbleiter gebildet ist.11. Solid-state solar cell according to claim 9, characterized in that the collector layer is formed from an optically transparent semiconductor.
12. Festkörpersolarzelle nach Anspruch 9 und 10, dadurch gekennzeichnet, daß das Substrat ein Glassubstrat ist.12. Solid-state solar cell according to claim 9 and 10, characterized in that the substrate is a glass substrate.
13. Festkörpersolarzelle nach Anspruch 1, 8 und 9, dadurch gekennzeichnet, daß auf der dem einfallenden Licht zugewandten Schicht der Schichtenfolge eine Antireflexionsschicht angeordnet ist.13. Solid-state solar cell according to claim 1, 8 and 9, characterized in that an anti-reflection layer is arranged on the layer of the layer sequence facing the incident light.
14. Festkörpersolarzelle nach Anspruch 1, dadurch gekennzeichnet, daß die Schichtenfolge mittels Dünnschichttechniken herstellbar ist. 14. Solid-state solar cell according to claim 1, characterized in that the layer sequence can be produced by means of thin-film techniques.
PCT/DE1995/000485 1994-04-07 1995-04-07 Solid-state solar cell WO1995028008A1 (en)

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Publication number Priority date Publication date Assignee Title
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