Buffer layer for front electrode structure in photovoltaic device or the like

• US 20080223430A1
• Filed: 03/14/2007
• Published: 09/18/2008
• Est. Priority Date: 03/14/2007
• Status: Abandoned Application

• Current Assignee: Guardian Glass LLC (KOCH Industries Incorporated)
• Original Assignee: Guardian Industries Corporation (KOCH Industries Incorporated)
• Inventors: Lu, Yiwei, Krasnov, Alexey
• Application Number:
  US11/717,787
• Publication Number:
  US 20080223430A1
• Time in Patent Office: Days
• US Class Current: 136/244
• CPC Class Codes: C03C 17/347 comprising a sulfide or oxysulfide
• CPC Class Codes: C03C 17/3476 comprising a selenide or telluride
• CPC Class Codes: C03C 17/36 at least one coating being a metal
• CPC Class Codes: C03C 17/3678 specially adapted for use in solar cells
• CPC Class Codes: C03C 2217/734 comprising an alternation of high and low refractive indexes
• CPC Class Codes: C03C 2217/944 Layers comprising zinc oxide
• CPC Class Codes: C03C 2217/948 Layers comprising indium tin oxide [ITO]
• CPC Class Codes: C23C 16/407 of zinc, germanium, cadmium, indium, tin, thallium or bismuth
• 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 31/03762 including only elements of Group IV of the Periodic Table
• CPC Class Codes: H01L 31/056 the light-reflecting means being of the back surface reflector [BSR] type
• CPC Class Codes: H01L 31/073 comprising only AIIBVI compound semiconductors, e.g. CdS/CdTe 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 31/1884 Manufacture of transparent electrodes, e.g. TCO, ITO
• CPC Class Codes: Y02E 10/543 Solar cells from Group II-VI materials
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product

Abstract

Certain example embodiments of this invention relate to an electrode structure (e.g., front electrode structure) for use in a photovoltaic device or the like. In certain example embodiments, a buffer layer (e.g., of or including tin oxide) is provided between the front electrode and the semiconductor absorber film in a photovoltaic device. The buffer layer may be deposited via sputtering, and may or may not be doped in certain example instances. In an example context of use in CdS/CdTe photovoltaic devices, the buffer layer is advantageous in that it (one or more of): (a) provides a good work-function match to a possible CdS/CdTe film and the front electrode; (b) provides good durability in that it is better able to withstand attacks of sulfur vapors at elevated temperatures during possible CdS/CdTe processing; (c) may be at least partially conductive; and/or (d) provides good mechanical durability.

Claims

1. A photovoltaic device comprising:

a front glass substrate;

an active semiconductor film;

an electrically conductive and substantially transparent front electrode located between at least the front glass substrate and the semiconductor film; and

a buffer film comprising tin oxide located between the front electrode and the semiconductor film.

2. The photovoltaic device of claim 1, wherein the buffer film directly contacts each of the front electrode and the semiconductor film.

3. The photovoltaic device of claim 1, wherein the buffer film has a work function of at least 4.3 eV.

4. The photovoltaic device of claim 1, wherein the buffer film comprising tin oxide is doped with Sb.

5. The photovoltaic device of claim 1, wherein the buffer film is from about 100 to 1,000 angstroms (Å

) thick.

6. The photovoltaic device of claim 1, wherein the buffer film is from about 150 to 600 Å

thick.

7. The photovoltaic device of claim 1, wherein the substantially transparent front electrode comprises one or more of:

indium-tin-oxide, zinc oxide, zinc aluminum oxide, and/or indium zinc oxide.

8. The photovoltaic device of claim 1, wherein the buffer film consists essentially of tin oxide which may optionally be doped with Sb.

9. The photovoltaic device of claim 1, wherein the buffer film is conductive and substantially transparent.

10. The photovoltaic device of claim 1, wherein the buffer film is less conductive, and thus has higher resistivity, than the front electrode.

11. The photovoltaic device of claim 1, wherein the semiconductor film comprises CdS and/or CdTe.

12. The photovoltaic device of claim 1, further comprising a back electrode, wherein the active semiconductor film is provided between at least the front electrode and the back electrode.

13. The photovoltaic device of claim 1, wherein the buffer film has a work-function of from about 4.0 to 5.7 eV.

14. The photovoltaic device of claim 1, wherein the buffer film has a work-function of from about 4.3 to 5.2 eV.

15. The photovoltaic device of claim 1, wherein the buffer film has a work-function of from about 4.5 to 5.0 eV.

16. An electrode structure for use in an electronic device, the electrode structure comprising:

an electrically conductive and substantially transparent electrode located between at least a substrate and a semiconductor film; and

a buffer film comprising tin oxide located between the electrode and the semiconductor film, wherein the buffer film has a conductivity less than that of the electrode.

17. The photovoltaic device of claim 16, wherein the buffer film directly contacts each of the electrode and the semiconductor film.

18. A method of making a photovoltaic device, the method comprising:

providing a glass substrate;

sputtering at least one target in an atmosphere in order to deposit a substantially transparent conductive electrode on the glass substrate;

sputtering at least one target comprising tin in order to deposit a buffer film comprising tin oxide on the glass substrate over at least the conductive electrode, thereby forming an electrode structure on the glass substrate; and

forming a photovoltaic device in which the electrode structure is coupled to an active semiconductor film in order to form the photovoltaic device.

19. The method of claim 18, wherein an atmosphere in which the target(s) used in forming the electrode and/or the buffer film is sputtered includes both argon and oxygen gas and has an oxygen gas to total gas ratio of from 0.00001 to 0.0025.

20. The method of claim 18, wherein the semiconductor film comprises amorphous silicon or CdTe.