Transparent conducting oxide for photovoltaic devices

• US 10,084,107 B2
• Filed: 11/30/2015
• Issued: 09/25/2018
• Est. Priority Date: 06/09/2010
• Status: Active Grant

• Current Assignee: Tesla Inc.
• Original Assignee: Tesla Inc.
• Inventors: Fu, Jianming, Xu, Zheng, Heng, Jiunn Benjamin, Yu, Chentao
• Primary Examiner(s): White, Sadie
• Application Number:
  US14/954,831
• Publication Number:
  US 20160087138A1
• Time in Patent Office: 1,030 Days
• CPC Class Codes: H01L 31/02167 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 31/072 the potential barriers being only of the PN heterojunction type
• CPC Class Codes: H01L 31/074 comprising a heterojunction with an element of Group IV of the Periodic Table, e.g. ITO/Si, GaAs/Si or CdTe/Si solar cells
• 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 31/1804 comprising only elements of Group IV of the Periodic Table
• CPC Class Codes: H01L 31/1868 Passivation
• CPC Class Codes: Y02E 10/547 Monocrystalline silicon PV cells
• 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

One embodiment of the present invention provides a solar cell. The solar cell includes a Si base layer, a passivation layer situated above the Si base layer, a layer of heavily doped amorphous Si (a-Si) situated above the passivation layer, a first transparent-conducting-oxide (TCO) layer situated above the heavily doped a-Si layer, a back-side electrode situated below the Si base layer, and a front-side electrode situated above the first TCO layer. The first TCO layer comprises at least one of: GaInO, GaInSnO, ZnInO, and ZnInSnO.

Claims

1. A photovoltaic structure, comprising:

a Si base layer;

a p-type doped amorphous Si layer positioned on a first side of the Si base layer;

an n-type doped semiconductor layer positioned on a second side of the Si base layer;

a first transparent-conductive-oxide layer positioned on and in direct contact with the p-type doped amorphous Si layer, wherein the first transparent-conductive-oxide layer has a work function that is greater than 5.7 eV and less than to 6.1 eV, thereby reducing potential barriers for carriers at an interface between the p-type doped amorphous Si layer and the first transparent-conductive-oxide layer; and

a second transparent-conductive-oxide layer positioned on and in direct contact with the n-type doped semiconductor layer, wherein the second transparent-conductive-oxide layer has a work function that is lower than the work function of the first transparent-conductive-oxide layer.

2. The photovoltaic structure of claim 1, further comprising a first metallic grid positioned on the first transparent-conductive-oxide layer, wherein the first metallic grid comprises an electroplated layer that includes Cu.

3. The photovoltaic structure of claim 1, further comprising a metallic grid positioned on the second transparent-conductive-oxide layer, wherein the metallic grid comprises an electroplated layer that includes Cu.

4. The photovoltaic structure of claim 1, wherein the Si base layer includes a crystalline-Si substrate or an epitaxially formed crystalline-Si thin film.

5. The photovoltaic structure of claim 1, further comprising at least one of:

a first passivation layer positioned between the Si base layer and the p-type doped amorphous Si layer; and

a second passivation layer positioned between the Si base layer and the p-type doped amorphous Si layer.

6. The photovoltaic structure of claim 5, wherein the first passivation layer and the second passivation layer include at least one of:

undoped amorphous Si and SiO_x.

7. The photovoltaic structure of claim 1, wherein the p-type doped amorphous Si layer comprises amorphous Si or amorphous Si containing carbon, and wherein the p-type doped amorphous Si layer has a doping concentration between 1×

10¹⁷/cm³ and 5×

10²⁰/cm³.

8. The photovoltaic structure of claim 1, further comprising a third transparent-conductive-oxide layer positioned on the first transparent-conductive-oxide layer, wherein the third transparent-conductive-oxide is selected from a group consisting of:

indium tin oxide (ITO), tin-oxide (SnO_x), aluminum doped zinc-oxide (ZnO;

Al), Ga doped zinc-oxide (ZnO;

Ga), and any combination thereof.

9. The photovoltaic structure of claim 1, wherein the second transparent-conductive-oxide layer comprises indium tin oxide (ITO).