Efficient thin film solar cell consisting of TCO/CdS/CuInS 2/CuGaS 2 structure

Abstract

The heterostructure consisting of a CuInS 2 absorber layer and a thin CuGaS 2 base layer was applied to a thin film solar cell. We studied the dependence of the current–voltage characteristics on chemical composition of the thin film. The heterostructure was found to have a beneficial effect on the cell performance under the following preparation conditions. In a first step, the Ga–Cu stacked precursor layer with a Cu to In ratio of 1.0 and a total thickness 240 nm was vacuum-evaporated onto a Mo-coated soda-lime glass substrate. It was then sulfurized in an Ar/H 2S mixture gas at 530 °C. The CuGaS 2 layer thus formed was treated in a KCN solution. In the next step, the In–Cu stacked precursor layer of 1 μm thickness was deposited on this surface. It was again sulfurized and treated as described above, resulting in the overall Cu to (In+Ga) ratio of 0.87. A 13% efficiency cell was obtained using the second precursor with a Cu to In ratio of 1.7.