Design and development of high-efficiency CdS/CdTe thin-film solar cells by enhancing absorption and minimizing recombination

Abstract

Second-generation solar cells, known as thin-film solar cells, have emerged as promising alternatives to traditional silicon-based first-generation photovoltaic cells. As the solar cell arrangement, superstrate configuration is the widely used structure for constructing thin-film solar cells. Nevertheless, less broadband light absorption due to light reflection from the front cover glass surface and carrier recombination at absorber layer back surface mainly contributes to less performance in thin-film solar cells. Herein, ZnO anti-reflection (AR) coating was introduced using spin coating technique on glass/FTO/CdS/CdTe/Cu/Au substrate to enhance the power conversion efficiency of the solar cell through reduction of front surface reflectance. The ZnO layer deposited at 3000 rpm in 15 s showed the minimum reflectance and higher transmittance over the 500-900 nm wavelength region. Further, the thickness of the optimal condition film was 63.32 nm, which was compatible with the ideal theoretical AR coating thickness of 65 nm. Comparing the device performances of the CdS/CdTe solar cell with AR coating and without AR coating, all tested devices have shown an average short circuit current density improvement of 6.7%, and the overall power conversion efficiency enhancement of 9%. Furthermore, a simulation study for CdTe solar cells was conducted using parameters of laboratory-developed solar cells. The variation between simulated and experimental data was discussed. Subsequently, to mitigate recombination at the back surface, the study suggested a solution: the introduction of a SnS back surface field (BSF) layer between the absorber layer and the back contact layer. This investigation was carried out using the SCAPS-1D simulation platform. According to the results obtained, the average power conversion efficiency was improved by 38%. Moreover, the simulation suggested that this approach could reduce the thickness of the CdTe layer, subsequently lowering manufacturing costs.