Photovoltaic device with layer region containing germanium therin

• US 5,279,681 A
• Filed: 02/20/1992
• Issued: 01/18/1994
• Est. Priority Date: 02/20/1991
• Status: Expired due to Fees

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Matsuda, Koichi, Murakami, Tsutomu, Okada, Naoto, Yamashita, Toshihiro, Matsuyama, Jinsho
• Primary Examiner(s): Weisstuch, Aaron
• Application Number:
  US07/838,101
• Time in Patent Office: 698 Days
• Field of Search: 136/255, 136/258 AM, 136/261, 257/458
• US Class Current: 136/255
• CPC Class Codes: H01L 31/022425 for solar cells
• CPC Class Codes: H01L 31/022466 made of transparent conductive layers, e.g. TCO, ITO layers
• CPC Class Codes: H01L 31/022475 composed of indium tin oxide [ITO]
• CPC Class Codes: H01L 31/022483 composed of zinc oxide [ZnO]
• CPC Class Codes: H01L 31/03765 including AIVBIV compounds or alloys, e.g. SiGe, SiC
• CPC Class Codes: H01L 31/03921 including only elements of Group IV of the Periodic Table
• CPC Class Codes: H01L 31/065 the potential barriers being only of the graded gap type
• CPC Class Codes: H01L 31/075 the potential barriers being only of the PIN type, e.g. amorphous silicon PIN solar cells
• CPC Class Codes: H01L 31/204 including AIVBIV alloys, e.g. SiGe, SiC
• CPC Class Codes: Y02E 10/548 Amorphous silicon PV cells
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product

Abstract

A photovoltaic device having a semiconductor body with a pin junction, with reduced time-dependent deterioration, high reliability and a high photoelectric conversion efficiency is disclosed.

An i-type semiconductor layer constituting the semiconductor body is composed of a layer having a region containing germanium and at least one region not containing germanium. The at least one region not containing germanium is provided at least at the side of a p-semiconductor layer. The maximum composition ratio of germanium in the region containing amorphous silicon and germanium is within a range from 20 to 70 at. %, and the composition ratio of germanium in the above-mentioned region containing amorphous silicon and germanium is zero at the side of an n-semiconductor layer and increases toward the side of the p-semiconductor layer, with the rate of increase being larger at the side of the n-semiconductor layer than at the side of p-semiconductor layer, and the composition ratio of germanium at the center of the i-layer thickness is at least equal to 75 at. % of the maximum composition ratio of germanium.

Claims

1. A photovoltaic device having a non-monocrystalline semiconductor body with a pin junction therein, wherein said semiconductor body comprises silicon atoms, an i-type semiconductor layer comprising a region containing germanium and at least one region substantially not containing germanium;

said at least one region not containing germanium being positioned at least at the side of a p-type semiconductor layer;

the maximum composition ratio of germanium in said region containing germanium is within a range from 20 to 70 at. %;

the composition ratio of germanium in said region containing germanium is zero at the side of an n-type semiconductor layer and increases toward the side of said p-type semiconductor layer, with a rate of increase larger at the side of said n-type semiconductor layer than at the side of said p-type semiconductor layer;

the composition ratio of germanium at the central position in the thickness of the i-type layer is at least equal to 75 at. % of the maximum composition ratio of germanium;

the maximum composition ratio of germanium being achieved at the interface of said p-type semiconductor layer with the region of the i-type layer containing the germanium; and

the energy band gap of the region substantially not including the germanium being narrower than the energy band gap of the p-type semiconductor layer but being wider than the energy band gap of the region including germanium, and light is incident said p-type semiconductor layer.

2. A photovoltaic device according to claim 1, wherein the bandgap of the i-type layer at the p-type and i-type layer interface is substantially smaller than the band gap of the n-type layer.