Influence of buffer layer on copper doped tin sulfide solar cell: A Numerical approach

Abstract

The proposed paper has examined the copper tin sulfide (CTS) semiconductor which is a ternary compound with extremely high absorption coefficient (105 cm−1) and ideal bandgap ranging from 0.9 to 1.6 eV. Non-toxic and widely available elements present on the earth constitute the elements of CTS. In this work, we have numerically simulated the structure: ITO coated polyethylene terephthalate (PET)/ZnO/(CdS, ZnS, CdZnS, TiO2)/CTS/Al using wx-AMPS software.In the structure different layers are: ITO coated PET which is a flexible substrate and acting as a front layer. It has been optimized by optimizing its layer thickness as 140 nm; ZnO as intrinsic layer; CdS/ZnS/CdZnS/TiO2 as buffer layers; CTS as absorber layer and Al as back contact. Different buffer layer variation was studied by varying its thickness and donor concentration. The QE curve shown in the result shows that at lower wavelength also, the QE value for CdZnS and TiO2 is high. Therefore, for furthermore investigation, these two buffer layers were considered. After optimizing the buffer layer, absorber layer optimization was carried out by varying its thickness, acceptor concentration and defect density values. By considering CdZnS as buffer layer, the optimized result which we got as, VOC = 0.819 V, JSC = 25.77 mA/cm2, FF = 85.59 %, η = 18.08 % and by considering TiO2 as buffer layer, the optimized result which we got as, VOC = 0.818 V, JSC = 25.55 mA/cm2, FF = 84.41 %, η = 17.66 %.