Improved performance of Cu(InGa)Se 2 thin-film solar cells using evaporated Cd-free buffer layers

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Polycrystalline Cu(InGa)Se 2 (CIGS) thin-film solar cells using evaporated In x Se y and ZnIn x Se y buffer layers are prepared. The purpose of this work is to replace the chemical bath deposited CdS buffer layer with a continuously evaporated buffer layer. In this study, a major effort is made to improve the performance of CIGS thin-film solar cells with these buffer layers. The relationship between the cell performance and the substrate temperature for these buffer layers is demonstrated. Even at the high substrate temperature of about 550°C for the buffer layer, efficiencies of more than 11% were obtained. Furthermore, the I− V characteristics of the cells using these buffer layers are compared with cells using CdS buffer layers fabricated by chemical bath deposition method. We have achieved relatively high efficiencies of over 15% using both the ZnIn x Se y and the CdS buffer layers.