Study on the prospects of Sb2Te3 back surface field in ZnCdS/ZnCdTe thin film solar cell

This paper numerically explores the possibility of high efficiency, ultrathin and stable ZnCdTe (CZT) polycrystalline solar cell using well accepted simulator AMPS-1D. The base line structure of the ZnCdTe cell (Glass/ITO/CdS/ZnCdTe/Back Contact) was the beginning point of this work and further this base line structure was modified to achieve ultrathin, higher efficiency and stable solar cell. In modified structure, CdS window layer has been replaced by a wide band gap material Zn_xCd_1-xS which increase the spectral response in the blue region as well as Zn_xCd_1-xS window layer was reduced to the extreme limit with insertion of a suitable buffer layer of ZnO in between ITO and window layer to check forward leakage current of ultrathin window layer. To lessen the back surface recombination loss and barrier height at back contact another extra layer (BSF p-Sb₂Te₃) has been inserted in between p-ZnCdTe layer and back contact (BC). Then the thickness of the window layer and absorber layer of the modified structure has been optimized. The modified structure with back surface field (BSF) layer (Glass/ ITO/ZnO/Zn_xCd_1-xS/Zn_xCd_1-xTe/Sb₂Te₃/BC) shows the highest efficiency of 23.17% (J_sc=33.50 mA/cm², FF=0.77% and V_oc= 0.98V). Finally the temperature effect on cell parameters was investigated and the overall temperature coefficient (TC) of the proposed cell is found to be 0.085%.