METHOD FOR ACTIVATING AN ABSORBER LAYER OF A THIN-FILM SOLAR CELL

Abstract

The invention refers to a method for activating an absorber layer of a semi-finished thin-film solar cell. The absorber layer comprises CdSe.sub.xTe.sub.1-x, CdSe, CdS or CdTe. The method comprises the steps of providing a semi-finished thin-film solar cell with an absorber layer comprising a CdSe.sub.xTe.sub.1-x, layer or comprising at least two layers selected from CdS, CdTe, ZnTe, CdSe, forming a polyvinylchloride film on a surface of the absorber layer, and performing a heat treatment of the semi-finished thin-film solar cell with the polyvinylchloride film on it, wherein the temperature is in the range of 300 C. to 500 C.

Claims

1. A method for activating an absorber layer of a semi-finished thin-film solar cell, the absorber layer comprising CdSe.sub.xTe.sub.1-x, CdSe, CdS or CdTe, the method comprising the steps of providing a semi-finished thin-film solar cell with an absorber layer comprising a CdSe.sub.xTe.sub.1-x, layer or comprising at least two layers selected from CdS, CdTe, ZnTe, CdSe, forming a polyvinylchloride film on a surface of the absorber layer, and performing a heat treatment of the semi-finished thin-film solar cell with the polyvinylchloride film on it, wherein the temperature is in the range of 300 C. to 500 C.

2. The method of claim 1, characterized in that the polyvinylchloride film is formed by applying a solid sheet of polyvinylchloride on the surface of the absorber layer.

3. The method of claim 1, characterized in that the polyvinylchloride film is formed by applying a solvent in which the polyvinylchloride is dissolved, followed by caking of the solvent.

4. The method of claim 3, characterized in that the solvent is an organic solvent.

5. The method of claim 1, characterized in that the method further comprises a cleaning step performed after the heat treatment in order to remove organic residuals resulting from the decomposed polyvinylchloride film.

6. The method of claim 5, characterized in that at least one of the group comprising an aqueous anorganic acid, an organic complexing agent, an organic complexing acid, a mechanical cleaning device, a water jet, ultra sound or plasma clean is used within the cleaning step.

7. The method of claim 2, characterized in that the method further comprises a cleaning step performed after the heat treatment in order to remove organic residuals resulting from the decomposed polyvinylchloride film.

8. The method of claim 3, characterized in that the method further comprises a cleaning step performed after the heat treatment in order to remove organic residuals resulting from the decomposed polyvinylchloride film.

9. The method of claim 4, characterized in that the method further comprises a cleaning step performed after the heat treatment in order to remove organic residuals resulting from the decomposed polyvinylchloride film.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification. The drawings illustrate an embodiment of the present invention and together with the description serve to explain the principles. Other embodiments of the invention are possible and lie within the scope of the invention. The elements of the drawings are not necessarily to scale relative to each other. Like reference numbers designate corresponding similar parts.

[0023] FIGS. 1 to 5 schematically show the sequence of process steps, including the activation step according to the invention using polyvinylchloride.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] FIG. 1 shows the semi-finished thin-film solar cell with a substrate (1), onto which a transparent front contact (2), and an absorber layer (3) comprising CdSe.sub.xTe.sub.1-x on top of it have already been applied.

[0025] FIG. 2 schematically shows a polyvinylchloride film (4) formed on the absorber layer (3). The polyvinylchloride film (4) is formed by applying a polyvinylchloride sheet having a thickness of 500 m with a roller. At this stage, the semi-finished thin-film solar cell is at room temperature

[0026] Then, the semi-finished thin-film solar cell is heated to a temperature of 400 C. and held at this temperature for 25 min for performing an activation process.

[0027] As schematically shown in FIG. 3, an activated absorber layer (31) remains after the activation process. The polyvinylchloride film is fully decomposed, but some residuals (41) have been left.

[0028] After cooling down the semi-finished thin-film solar cell, a cleaning step follows.

[0029] FIG. 4 schematically shows the cleaning step after the activation process. Here, a cleaning solution (5) containing dimethylformamide (DMF) is used to remove residuals (41) of the polyvinylchloride film. The cleaning step is carried out at a temperature of 20 C. for 30 seconds. To this end, the semi-finished thin-film solar cell is dipped into the cleaning solution (5) (DMF 50% to 100%).

[0030] FIG. 5 schematically shows the layer sequence of the finished solar cell after applying a back contact (6) onto the activated absorber layer (31).

[0031] The embodiments of the invention described in the foregoing description are examples given by way of illustration and the invention is nowise limited thereto. Any modification, variation and equivalent arrangement as well as combinations of embodiments should be considered as being included within the scope of the invention.

REFERENCE NUMERALS

[0032] 1 Substrate [0033] 2 Front contact [0034] 3 Absorber layer [0035] 31 Activated absorber layer [0036] 4 Polyvinylchloride film [0037] 5 Cleaning solution [0038] 6 Back contact