Thin film photovoltaic device

• US 4,342,879 A
• Filed: 10/24/1980
• Issued: 08/03/1982
• Est. Priority Date: 10/24/1980
• Status: Expired due to Term

• Current Assignee: University of Delaware A Not-For-Profit Corporation of de
• Original Assignee: University of Delaware
• Inventors: Bhushan, Manjul, Catalano, Anthony W.
• Primary Examiner(s): Weisstuch, Aaron
• Application Number:
  US06/200,447
• Time in Patent Office: 648 Days
• Field of Search: 136/260, 136/256, 136/258, 136/265, 357/30, 357/65, 357/67, 357/59, 357/61
• US Class Current: 136/265
• CPC Class Codes: H01L 31/022466 made of transparent conductive layers, e.g. TCO, ITO layers
• CPC Class Codes: H01L 31/032 including, apart from doping materials or other impurities, only compounds not provided for in groups H01L31/0272 - H01L31/0312
• CPC Class Codes: H01L 31/0392 including thin films deposited on metallic or insulating substrates ; characterised by specific substrate materials or substrate features or by the presence of intermediate layers, e.g. barrier layers, on the substrate textured substrates H01L31/02366
• CPC Class Codes: H01L 31/068 the potential barriers being only of the PN homojunction type, e.g. bulk silicon PN homojunction solar cells or thin film polycrystalline silicon PN homojunction solar cells
• CPC Class Codes: Y02E 10/547 Monocrystalline silicon PV cells

Abstract

A thin film photovoltaic solar cell which utilizes a zinc phosphide semiconductor is of the homojunction type comprising an n-type conductivity region forming an electrical junction with a p-type region, both regions consisting essentially of the same semiconductor material. The n-type region is formed by treating zinc phosphide with an extrinsic dopant such as magnesium. The semiconductor is formed on a multilayer substrate which acts as an opaque contact. Various transparent contacts may be used, including a thin metal film of the same chemical composition as the n-type dopant or conductive oxides or metal grids.

Claims

1. In a photovoltaic device having an ohmic back contact and a transparent electrical contact with at least one semiconductor layer therebetween of a material of the type formed by high temperature growth, the improvement being said device is a homojunction with said semiconductor layer having one region of p-type conductivity and an adjacent region of n-type conductivity with the electrical junction therebetween, said semiconductor layer being made of a material from the class of isostructural compounds comprised of elements selected from Groups IIB and VA of the Periodic Table, and said n-type conductivity region of said semiconductor layer being extrinsically doped with an element selected from groups IA and IIA of the Periodic Table.

2. In the device of claim 1 wherein said transparent electrical contact is made from a material capable of acting as said extrinsic n-type conductivity doping agent.

3. In the device of claim 2 wherein said semiconductor is made from zinc phosphide, and said transparent electrical contact material is magnesium.

4. In the device of claim 1 wherein said transparent electrical contact is a metallization pattern having substantial open spaces.

5. In the device of claim 1 wherein said transparent electrical contact is a metallization pattern having substantial open areas, and a continuous window layer is disposed between said metallization pattern and said n-type conductivity region.

6. In the device of claim 5 wherein said window layer is a thin metal film made from a material capable of acting as said extrinsic n-type conductivity doping agent.

7. In the device of claim 1 wherein said ohmic back contact is a multilayer substrate capable of withstanding the high temperature for forming said semiconductor layer, said substrate layers including a layer remote from said semiconductor layer comprising a support on which all of the other layers of said device are formed, said substrate layers including a layer having an expansion coefficient equal to or slightly greater than the expansion coefficient of said semiconductor layer, said substrate layers including a metal layer of high conductivity, and said substrate layers including a barrier layer adjacent said semiconductor layer which comprises a diffusion barrier and further comprises adherent means for causing said barrier layer to adhere to said metal layer.

8. In the device of claim 7 wherein said barrier layer is a different layer than said metal layer, and an intermediate layer being between said barrier layer and said metal layer formed by the reaction of said barrier and metal layers.