Photovoltaic Device Including a CZTS Absorber Layer and Method of Manufacturing the Same

• US 20130074911A1
• Filed: 09/23/2011
• Published: 03/28/2013
• Est. Priority Date: 09/23/2011
• Status: Abandoned Application

• Current Assignee: NEO Solar Power Corporation
• Original Assignee: NEO Solar Power Corporation
• Inventors: Liao, Yueh-Chun, Yang, Feng-Yu, Ting, Ching
• Application Number:
  US13/241,248
• Publication Number:
  US 20130074911A1
• Time in Patent Office: Days
• US Class Current: 136/255
• CPC Class Codes: H01L 31/0326 comprising AIBIICIVDVI kesterite compounds, e.g. Cu2ZnSnSe4, Cu2ZnSnS4
• CPC Class Codes: H01L 31/072 the potential barriers being only of the PN heterojunction type
• CPC Class Codes: Y02E 10/50 Photovoltaic [PV] energy

Abstract

A photovoltaic device including a CZTS absorber layer and method for manufacturing the same are disclosed. The photovoltaic device includes a substrate, a bottom electrode, an absorber layer formed on the bottom electrode, a buffer layer formed on the absorber layer and a top electrode layer formed on the buffer layer. The absorber layer includes a first region adjacent to the bottom electrode and a second region adjacent to the first region. Both of the first region and the second region include a formula of Cu_a(Zn_1-bSn_b)(Se_1-cS_c)₂, wherein 0<a<1, 0<b<1, 0≦c≦1 and a Zn/Sn ratio of the first region is higher than that of the second region.

Claims

1. A photovoltaic device including a CZTS absorber layer, comprising:

a substrate;

a bottom electrode;

an absorber layer, formed on the bottom electrode;

a buffer layer, formed on the absorber layer; and

a top electrode layer, formed on the buffer layer;

wherein the absorber layer includes a first region adjacent to the bottom electrode and a second region adjacent to the first region, both of the first region and the second region include a formula of Cu_a(Zn_1-bSn_b)(Se_1-cS_c)₂, wherein 0<

a<

1, 0<

b<

1, 0≦

c≦

1 and a Zn/Sn ratio of the first region is higher than that of the second region.

2. The photovoltaic device according to claim 1, wherein a thickness of the second region of the absorber layer is larger than that of the first region of the absorber layer.

3. The photovoltaic device according to claim 1, wherein the second region of the absorber layer is adjacent to the buffer layer.

4. The photovoltaic device according to claim 1, wherein the bottom electrode layer includes a material selected from a group consisted of molybdenum (Mo), tungsten (W), aluminum (Al), and Indium Tin Oxide (ITO).

5. The photovoltaic device according to claim 1, wherein the buffer layer includes an n-type semiconductor layer.

6. The photovoltaic device according to claim 5, wherein the n-type semiconductor layer includes a material selected from a group consisted of cadmium sulfide (CdS), Zn(O,OH,S), indium selenide (In₂Se₃), zinc sulfide (ZnS), and zinc magnesium oxide (Zn_xMg_1-xO).

7. The photovoltaic device according to claim 1, wherein the top electrode layer includes a material selected from a group consisted of zinc oxide (ZnO), indium tin oxide (ITO), boron-doped zinc oxide (B—

ZnO), aluminum-doped zinc oxide (Al—

ZnO), gallium-doped zinc oxide (Ga—

ZnO), and antimony tin oxide (ATO).

8. The photovoltaic device according to claim 1, wherein the Zn/Sn ratio of the first region is of about 1.22 to about 2.0.

9. The photovoltaic device according to claim 1, wherein the Zn/Sn ratio of the second region is of about 0.83 to about 1.22.

10. A method for manufacturing a photovoltaic device including a CZTS absorber layer, comprising:

forming a bottom electrode on a substrate;

forming an absorber layer including a gradient composition region on the bottom electrode layer;

forming a semiconductor layer on the absorber layer; and

forming a top electrode layer on the semiconductor layer;

wherein the absorber layer includes a formula of Cu_a(Zn_1-bSn_b)(Se_1-cS_c)₂, wherein 0<

a<

1, 0<

b<

1, 0≦

c≦

1, and the gradient composition region includes gradient Zn/Sn ratio and a higher Zn/Sn ratio at a side adjacent to the bottom electrode layer.

11. The method according to claim 10, wherein the step of forming the absorber layer includes at least one selected from the group consisted of coating, electron-beam evaporation, vapor deposition, sputtering, electro-plating, or sol-gel method, spray pyrolysis, spray deposition, radiofrequency magnetron sputtering and electrochemical deposition.

12. The method according to claim 10, wherein the step of forming the gradient composition region of the absorber layer includes:

forming a first precursor layer with a first Zn/Sn ratio on the bottom electrode layer;

forming a second precursor layer with a second Zn/Sn ratio which is lower than the first Zn/Sn ratio on the first precursor layer; and

annealing the first precursor layer and the second precursor layer.

13. The method according to claim 12, further comprising:

coating a first precursor solution to form a first liquid layer on the bottom electrode layer;

drying the first liquid layer to form the first precursor layer; and

coating a second precursor solution to form a second liquid layer on the first precursor layer; and

drying the second liquid layer to form the second precursor layer.

14. The method according to claim 13, further comprising forming the second precursor layer with a thickness larger than that of the first precursor layer.

15. The method according to claim 13, wherein at least one of the first precursor solution and the second precursor solution includes hydrazine-based precursor solutions or non-hydrazine-based precursor solutions.

16. The method according to claim 13, wherein at least one of the step of coating the first precursor solution and the step of coating the second precursor solution includes at least one method selected from the group consisted of drop casting, spin coating, dip coating, doctor blading, curtain coating, slide coating, spraying, slit casting, meniscus coating, screen printing, ink jet printing, pad printing, flexographic printing and gravure printing.

17. The method according to claim 13, wherein the drying step is performed at a temperature of about 25°

C. to about 600°

C.

18. The method according to claim 13, wherein the annealing step is performed at a temperature of about 300°

C. to about 700°

C.

19. A method for manufacturing a photovoltaic device including a CZTS absorber layer, comprising:

forming a bottom electrode on a substrate;

coating a first CZTS precursor solution to form a first precursor layer on the bottom electrode layer;

coating a second CZTS precursor solution to form a second precursor layer on the first precursor layer;

heating the first precursor layer and the second precursor layer to form the CZTS absorber layer;

forming a semiconductor layer on the CZTS absorber layer; and

forming a top electrode layer on the semiconductor layer;

wherein the first CZTS precursor solution includes a higher Zn/Sn ratio than that of the second CZTS precursor solution.

20. The method according to claim 19, further comprising forming the second precursor layer with a thickness larger than that of the first precursor layer.