The role of back surface field SnS layer in improvement of efficiency of CdTe thin film solar cells

A one-dimensional simulator Analysis of Microelectronic and Photonic Structures in 1 Dimension (AMPS-1D) has been used so as to investigate cadmium telluride (CdTe) based solar cells properties. The aim of the current study is to explore the possibility of improving the efficiency of the solar cells. For that purpose, a novel back surface field (BSF) SnS layer has been inserted after the back contact (Ni) in CdTe solar cells constituted by a pile of thin layers that contains in particular a fine layer called buffer layer (CdS) between the absorber layer CdTe and the windows layer ZnO-Al. The optimal values ​that​ give the maximum performance of the structure ZnO/CdS/CdTe/SnS/Ni, with and without a BSF layer (SnS) has been determined. Our results show an improvement of the efficiency of the solar cell when using the BSF. The proposed cell with SnS layer is found to give an efficiency of 21.83% using only thicknesses of 0.6 μm and 0.4 μm for CdTe and SnS, respectively. However, the efficiency of the cell reference (without BSF) is 17.40% with a thickness of 1 μm for the absorber layer CdTe. Moreover, the normalized efficiency of the proposed cells with BSF layer decreases linearly with increasing the temperature, suggesting a better stability of the ultra thin cells.