# US 4,393,267 A · Method for improving the efficiency of a solar cell and an improved cadmium sulfide/copper sulfide photovoltaic cell

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- Number: US 4,393,267 A
- Document ID: US4393267A
- Status: Granted
- Kind: A
- Application number: 06/278,799
- Filed: 1981-06-29
- Granted: 1983-07-12
- Earliest claimed: 1981-05-26
- Assignees: Chevron Research Company
- Inventors: Terry M. Peterson
- Web page: https://patentgrep.com/patent/US4393267A

## CPC

- H10F 71/00: Manufacture or treatment of devices covered by this subclass (patterning processes to connect thin photovoltaic cells in integrated devices, or assemblies of multiple devices, having photovoltaic cells H10F19/33; manufacture or treatment of encapsulations or containers for integrated devices, or assemblies of multiple devices, having photovoltaic cells H10F19/80; manufacture or treatment of integrated devices, or assemblies of multiple devices, comprising at least one element in which radiation controls the flow of current H10F39/00)
- H10F 71/125: {The active layers comprising only Group II-VI materials, e.g. CdS, ZnS or CdTe}
- H10F 10/16: Photovoltaic cells having only PN heterojunction potential barriers
- H10F 10/169: {comprising Cu2X/CdX heterojunctions, wherein X is a Group VI element, e.g. Cu2O/CdO PN heterojunction photovoltaic cells}
- Y02E 10/50: Photovoltaic [PV] energy
- 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

## Abstract

A CdS/Cu.sub.x S solar cell and method of fabricating the solar cell. The CdS layer of the solar cell is fabricated on a conductive substrate and forms an ohmic contact thereto. Thereafter, a layer of Cu.sub.x S is fabricated on the CdS layer and the combined structure is rinsed in an aqueous acidic rinse having a pH less than about pH3 prior to curing the device in hydrogen at an elevated temperature and fabricating a copper containing electrical contact to the Cu.sub.x S layer. The rinsing of the device prior to curing improves the performance of the finished solar cell.

## Claims

### Claim 1

A method of fabricating a solar cell, comprising:
(a) fabricating a layer of CdS on a conductive substrate and forming an ohmic contact thereto;
(b) fabricating a Cu.sub.x S layer on said layer of CdS;
(c) rinsing the device of the previous steps (a) and (b) in an aqueous acid rinse having a pH less than about pH 3;
(d) curing the device of step (c) in H.sub.2 at an elevated temperature; and
(e) fabricating an electrical contact to said copper-containing layer.

### Claim 2 (depends on 1)

The method according to claim 1, wherein the rinse is from about 10 to 50 seconds.

### Claim 3 (depends on 2)

The method according to claim 2 wherein the acid in the aqueous rinse is a reducing acid with respect to Cu.sup.++ ions.

### Claim 4 (depends on 2)

The method according to claim 2, wherein the acid in the aqueous rinse is selected from the group consisting of hydrochloric acid, sulfuric acid, hydrobromic acid, and hydrofloric acid.

### Claim 5 (depends on 3, 4)

The method according to claim 3 or 4, wherein the pH is adjusted to less than about pH 2.

### Claim 6 (depends on 5)

The solar cell fabricated according to claim 5.

### Claim 7

In a method of fabricating a CdS/Cu.sub.x S solar cell, the improvement which comprises:
(a) rinsing the CdS/Cu.sub.x S layers in an aqueous rinse having an acid which is reducing with respect to Cu.sup.++ ions and a pH of less than about pH 3 prior to forming an electrical contact to the Cu.sub.x S layer.

### Claim 8 (depends on 7)

The solar cell fabricated according to claim 7.