# US 2021/0280735 A1 · DIFFUSION BASED EX-SITU GROUP V (P, As, Sb, Bi) DOPING IN POLYCRYSTALLINE CdTe THIN FILM SOLAR CELLS

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- Number: US 2021/0280735 A1
- Document ID: US20210280735A1
- Status: Published application
- Kind: A1
- Application number: 17/190,664
- Filed: 2021-03-03
- Published: 2021-09-09
- Earliest claimed: 2020-03-03
- Assignees: The Board of Trustees of The University of Alabama; The University of Toledo
- Applicants: The Board of Trustees of the University of Alabama; The University of Toledo
- Inventors: Feng Yan; Yanfa Yan
- Web page: https://patentgrep.com/patent/US20210280735A1

## CPC

- H10F 71/125: {The active layers comprising only Group II-VI materials, e.g. CdS, ZnS or CdTe}
- H10F 71/128: {Annealing}
- H10F 77/1233: {characterised by the dopants}
- H10F 77/211: {for photovoltaic cells}
- H10F 10/162: comprising only Group II-VI materials, e.g. CdS/CdTe photovoltaic cells
- Y02E 10/543: Solar cells from Group II-VI materials
- Y02P 70/50: Manufacturing or production processes characterised by the final manufactured product
- H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS

## Abstract

Described herein is a diffusion-based ex-situ group V element doping method in the CdCl2 heat-treated polycrystalline CdTe film. The ex-situ doping using group V halides, such as PCl3, AsCl3, SbCl3, or BiCl3, demonstrated a promising PCE of ˜18% and long-term light soaking stability in CdSe/CdTe and CdS/CdTe devices with decent carrier concentration>1015 cm−3. This ex-situ solution or vapor process can provide a low-cost alternative pathway for effective doping of As, as well as P, Sb, and Bi, in CdTe solar cells with limited deviation from the current CdTe manufacturing process.

## Claims

### Claim 1

A method of ex-situ doping cadmium telluride (CdTe) with P, As, Sb, or Bi, comprising:
a) depositing a cadmium telluride (CdTe) film onto a substrate;
b) heat-treating the cadmium telluride film with cadmium chloride (CdCl2); and then
c) contacting the heat-treated cadmium telluride film with a solution or vapor comprising P halide, As halide, Sb halide, or Bi halide, to thereby provide a cadmium telluride film doped with P, As, Sb, or Bi.

### Claim 2 (depends on 1)

The method of claim 1, wherein the substrate further comprises a cadmium selenide, cadmium sulfide, or ZnMgO buffer layer.

### Claim 3 (depends on 1)

The method of claim 1, wherein the cadmium telluride film is polycrystalline.

### Claim 4 (depends on 1)

The method of claim 1, wherein depositing the cadmium telluride film onto the substrate is performed in the absence of P, As, Sb, or Bi.

### Claim 5 (depends on 1)

The method of claim 1, wherein depositing the cadmium telluride film is by closed space sublimation, vapor transport deposition, metal-organic chemical vapor deposition, electrodeposition, elemental vapor transport, or molecular beam epitaxy.

### Claim 6 (depends on 1)

The method of claim 1, wherein the substrate is a transparent conducting oxide (TCO) selected from indium doped tin oxide (ITO), fluorine-doped tin oxide (FTO), aluminum-doped ZnO (AZO), or a combination thereof.

### Claim 7 (depends on 1)

The method of claim 1, wherein contacting the heat-treated cadmium telluride film with the solution or vapor is by spin coating, dip coating, slot die, or spraying the solution or vapor onto the cadmium telluride film.

### Claim 8 (depends on 1)

The method of claim 1, wherein contacting the heat-treated cadmium telluride film with the solution or vapor is done under a dry inert gas.

### Claim 9 (depends on 1)

The method of claim 1, wherein the solution or vapor comprises from about 1 to about 1,000 mg/L of the P halide, As halide, Sb halide, or Bi halide.

### Claim 10 (depends on 1)

The method of claim 1, wherein the solution or vapor comprises about 10 mg/L of the P halide, As halide, Sb halide, or Bi halide.

### Claim 11 (depends on 1)

The method of claim 1, wherein after the heat-treated cadmium telluride film is coated with the solution or vapor, the film is further contacted with graphite or a metal contact.

### Claim 12 (depends on 1)

The method of claim 1, wherein after the heat-treated cadmium telluride film is coated with the solution or vapor the film is further heated to activate the P, As, Sb, or Bi, dopants in the film.

### Claim 13 (depends on 1)

The method of claim 1, wherein the P halide, As halide, Sb halide, or Bi halide is AsCl3, PCl3, SbCl3, or BiCl3.

### Claim 14 (depends on 1)

The method of claim 1, wherein the heat-treated cadmium telluride film is contacted with a solution or vapor of AsCl3.

### Claim 15 (depends on 1)

The method of claim 1, wherein the solution further comprises methanol, ethanol, propanol, isopropanol, butanol, pentanol, benzene, carbon sulfide, or a combination thereof.

### Claim 16 (depends on 1)

The method claim 1, wherein heat-treating the films is performed at a temperature from about 200° C. to about 600° C.

### Claim 17 (depends on 1)

The method of claim 1, wherein after the cadmium telluride film is heat treated, but before it is contacted with the solution or vapor, the cadmium telluride film is cleaned.

### Claim 18 (depends on 1)

The method claim 1, wherein contacting the heat-treated cadmium telluride film with a solution or vapor is done at a temperature of less than about 400° C.