GB2450324A - Semiconducting transition metal oxide photovoltaic devices - Google Patents

Abstract

Junctions between n-type and p-type transition metal oxide semiconductor layers are used to fabricate solar cells on insulating and conductive substrates.

Description

I

PATENT APPLICATION FOR A METHOD OF PRODUCING TRANSITION METAL

OXIDE PHOTOVOLTAIC DIODES CAPABLE OF GENERATING ELECTRICAL

ENERGY WHEN EXPOSED TO DAYLIGHT

APPLICANT: Mr Jeffery Boardman BSc(Eng)

32 Burfield Drive

Appleton Nr Wamngton Cheshire WA4 5DA REFERENCE: J.B.D.R-1 TITLE: A method of producing daylight reactive transition metal oxide photovoltaic diodes

DESCRIPTION

The present invention relates to a method of producing photovoltaic diode devices from combinations of n' and p' type transition and other metal oxides which will convert visible light into electrical energy.

There are existing devices which generate electrical energy from sunlight based on the use of silicon, germanium and other materials, which are in widespread use throughout the world.

The disadvantages of utilising diodes based on silicon, germanium or similar materials are that 1. They are expensive to produce, requiring the use of highly toxic materials in their manufacture.

2. The production process requires complex high cost equipment and clean room' conditions.

3. Are currently produced in relatively small size, only cms square.

4. Cannot withstand atmospheric corrosion without external protection and support, which reduces the amount of incident photons available for energy conversion and consequently their efficiency.

The present invention seeks to overcome these pre-mentioned disadvantages and provide more robust, larger, efficient and longer lasting diodes on a more cost effective basis.

In accordance with the first aspect of the present invention there is provided a diode comprised of an electrically insulating substrate onto which is thermally deposited a semi-conductive transition metal oxide layer, generally of the n' type, covering 80% of the substrate area and having a narrow band or strip of conductive metal, generally copper, flame spray deposited along one side or edge. Onto this first-mentioned semi-conductive metal oxide layer is deposited a second, transparent, semi-conductive metal oxide layer, generally of p' type, such that the junction between the n' and p' type semi-conductive metal oxide layers forms a depletion layer, or Schotky bamer, and subsequently a narrow band of electrically conducted metal is applied to the opposite edge or side of the substrate to that on which the first narrow band or strip of conductive metal was applied. The second transparent semi-conductive metal oxide layer is applied also to 80% of the substrate area such that it covers the exposed 20% of the substrate area and 60% of the firstly deposited a' type semi-conductive transition metal oxide layer so as to form a reactive photovoltaic diode onto 60% of the substrate area.

It is a second aspect of this present invention that the semi-conductive transition metal oxides which comprise the diode described in the first aspect may be applied in any order, n' type first with p' type second, or p' type first and n' type second, as may be advantageously required.

In accordance with a third aspect of the present invention there is provided a diode comprised of a metal substrate onto which is thermally deposited a semi-conductive transition metal oxide layer, generally of an n' type, applied over the whole area of the electrically conductive metal substrate. A second p' type layer of a transparent semi-conductive transition or other metal oxide layer is deposited onto the pre-mentioned first oxide layer, but covering a lesser area, such that the junction between the a' and p' type semi-conductive transition or other metal oxide layers forms a depletion layer or Schotky barrier, and subsequently to the outer surface of the second semi-conductive oxide layer is applied an electrically conductive contact material such that when the diode so produced is exposed to incident photon radiation and connections are made to the metal substrate and the pre-mentioned conductive contact final layer, an electrical current may be seen to flow in an external circuit.

It is a fourth aspect of this present invention that the n' and p' type semi-conductive metal oxides comprising the diodes previously described in aspects one and three inclusively may be any combination of two or more transition metals in alloy or other form, and may incorporate other elements from the lanthanide, actinides, semi-metals or non-metal groups of the Periodic Table.

It is a fifth aspect of this present invention that the semi-conductive transition and other metal oxides pre-mentioned in the fourth aspect may have different activation energies, dependent upon their composition, and that diodes comprised of these oxides will be produced having different band gap values by virtue of utilising combinations of n' and p' type semi-conductive transition and other metal oxides having different activation energies determined by their composition.

It is a sixth aspect of this present invention that the pre-mentioned semi-conductive transition and other metal oxides may be produced by the reaction of oxygen with a transition metal alloy in powder or other form under the influence of heat or by any form of chemical reaction required to provide semi-conductive transition metal oxides with the necessary properties.

It is a seventh aspect of this present invention that the production of semi-conductive transition and other metal oxides by the reaction of oxygen with a transition metal alloy in powder or other form under the influence of heat may be performed as a separate process prior to deposition of the semi-conductive transition metal oxides onto the metallic substrate or as part of the deposition process.

It is an eighth aspect of this present invention that the processes utilised to apply the semi-conductive transition and other metal oxides to the substrate may incorporate any of the known thermal deposition processes and/or physical or chemical vapour deposition techniques and equipment.

It is a ninth aspect of this present invention that the thicknesses of the semi-conductive transition and other metal oxide n' and p' type layers applied to the metal substrate may be varied in thickness as is advantageously required by variations of the deposition process parameters utilised to apply the said semi-conductive oxides to the substrate as pre-mentioned in aspect eight.

It is a tenth aspect of this present invention that the diode substrate may be comprised of any electrically conductive metal or alloy in flat, tubular or spherical form, or any combination of these forms, and additionally the diode substrate may be comprised of any electrically insulating substance.

It is an eleventh aspect of this present invention that electrically conductive layers deposited onto the outer surface of the semi-conductive transition and other metal oxide layers of a diode may be comprised of any electrically conductive metal, metal alloy or other material, and may be applied by any of the means pre-mentioned in the ninth aspect and additionally by mechanical or adhesive processes.

lt is a twelfth aspect of this present invention that where the process utilised to deposit the second oxide layer does not result in the required transparent form but in a form where the oxide is polycrystalline and opaque to daylight then the opaque poly-crystalline oxide form may be converted to a transparent crystalline or amorphous form by the application of thermal or other energy and that the application of such thermal or other energy may be by means of a laser or other high energy beam, or any conventional heat treatment process.

It is a further aspect of this present invention that the pre-mentioned diodes may be comprised of more than two combinations of n' and p' type semi-conductive transition and other metal oxides, and that these semi-conductive transition and other metal oxide layers may be applied to both surfaces of a substrate such as to be exposed to photon radiation from more than one direction.

It is another aspect of this present invention that the sizes of the diodes which are produced by the pre-mentioned aspects and processes are not limited in dimensions but may be manufactured in areas of square metres with consequent increase in power over existing current sificon or germanium based devices.

Claims (14)

1. A method of constructing a photovoltaic diode capable of generating electrical energy from exposure to daylight radiation, the method comprising the steps of: (a) Preparing the surface of an electrically insulating supporting substrate such that it is chemically clean.

   (b) Depositing onto the substrate surface a layer of semi-conductive transition or other metal oxides generaHy, but not exclusively, having n' type electronic properties such that this first layer only partially covers the substrate surface from one edge outwards.

   (C) Depositing a thin band or track of electrically conductive metal to that area of the first semi-conductive transition or other metal oxide situated at one edge of the substrate.

   (d) Depositing a second optically transparent layer of semi-conductive transition or other metal oxides onto the pre-mentioned partially coated substrate and first oxide layer such that this second oxide layer which has p' type electronic properties covers the uncoated area of the substrate and overlaps onto the pre-mentioned first oxide layer but does not extend to or impinge onto the pre-mentioned narrow band or track of electically conductive metal overlaying the first oxide layer along one edge of the substrate such that the area where the second optically transparent semi- conductive transition or other metal oxide layer overlaps onto the pre-mentioned first semi-conductive transition or other metal oxide layer, a diode is formed such that at the junction between the n' and p' type semi-conductive metal oxide layers there is a depletion layer or Schotky barrier.

   (e) Depositing a thin band or track of electrically conductive metal to that area of the second layer of semi-conductive transition or other metal oxide situated at the opposite edge of the substrate to the thin conductive metal track applied to the first semi-conductive oxide layer.
2. 2. A method of constructing a photovoltaic diode capable of generating electrical energy from exposure to daylight radiation, the method comprising the steps of (a) Preparing the surface of a supporting substrate such that the surface is chemically dean and electrically conductive.

   (b) Depositing onto the substrate a layer of semi-conductive transition or other metal oxides generally, but not exdusively, having a' type electronic properties.

   (C) Depositing onto the first layer of semi-conductive metal oxides a second optically transparent layer having opposite electronic characteristics to the first oxide layer, but being lesser in area such that at the junction between the two electronically different semi-conductive transition or other metal oxide layers a depletion layer or Schotky barrier is formed.

   (d) Depositing an electrically conducting layer onto the second semi-conductive transition or other metal oxide layer but being lesser in area.
3. 3. A claim as in Claims (1) and (2) whereby the n' and p' type semi-conductive metal oxides may be produced from any combination of two or more transition metals in alloy or other forms and may incorporate other elements from the fanthanide, actinides, semi-metals or non-metal groups of the Periodic Table.
4. 4. A claim as in Claims (1), (2) and (3) that the pre-mentioned semi-conductive transition or other metal oxides may be produced by the reaction of oxygen with the metals in powder form under the influence of heat or by any form of chemical reaction required to provide the semi-conductive oxides with the requisite n' and p' type properties.
5. 5. A claim as in Claims (1) to (4) inclusively whereby the processes uthised to apply the semi-conductive transition or other metal oxides to the supporting substrate matenals may incorporate any of the known thermal deposition processes and/or physical or chemical vapour deposition and/or magnetron sputtering techniques and equipment
6. 6. A claim as in Claims (1) to (5) inclusively whereby the production of semi-conductive transition or other metal oxides by the reaction with oxygen in powder or other form under the influence of heat may be performed as a separate process prior to the deposition of the semi-conductive oxides onto the substrate or as part of the deposition process.
7. 7. A claim as in Claims (1) to (6) inclusively whereby the thicknesses of the semi-conductive transition or other metal oxide n' and p' type layers applied to the supporting substrate materials may be varied in thickness as is advantageously required by variations of the deposition process parameters utilised to apply the said semi-conductive oxides to the substrate.
8. 8. A claim as in Claims (1) to (7) inclusively whereby the semi-conductive transition and other metal oxides may have different activation energies dependent upon their composition and that diodes comprised of different oxide combinations may be produced having different band gap values.
9. 9. A claim as in Claims (1) to (8) inclusively whereby the deposition of the first semi-conductive transition or other metal oxide to the supporting substrate materials utilises thermal deposition techniques.
10. 10. A claim as in Claims (1) to (9) inclusively whereby the deposition of the second optically transparent semi-conductive transition or other metal oxide layer utilises physical or vapour deposition or magnetron sputtering techniques and equipment.
11. 11. A claim as in Claims (1) to (10) inclusively whereby any crystalline defects which impair the optical transparency of the second semi-conductive transition or other metal oxide layer may be alleviated by the application of thermal or other forms of energy from laser or other high energy beam equipment.
12. 12. A claim as in Claims (1) to (11) inclusively whereby the substrate materials may be of any electrically conductive metal, in flat tubular or spherical form, or any combination of these forms, and additionally the substrate may be comprised of any electrically insulating substance either plain or with an electrically conductive layer applied to it.
13. 13. A claim as in Claim (5) whereby the electrically conductive layers deposited onto the surfaces of the semi-conductive transition or other metal oxide layers may be comprised of any electrically conductive metal, metal alloy or other material, and may be applied by any of the means pre-mentioned in Claim (5) and additionally be mechanical or adhesive processes.
14. 14. A claim as in Claims (1) to (13) inclusively whereby the daylight reactive diodes may be comprised of more than two combinations of n' and p' type semi-conductive transition and other metal oxides and that these semi-conductive oxides may be applied to both surfaces of a substrate such as to be exposed to photon radiation from more than one direction.