Investigation of buffer layers, front and back contacts for ZnxCd1−xS/CdTe photovoltaic

A numerical analysis has been performed utilizing Analysis of Microelectronic and Photonic Structures (AMPS 1D) simulator to explore the possibility of higher efficiency and stable ZnxCd1−xS/CdTe cells. Several cell structures with indium tin oxide (ITO) and cadmium stannate (Cd2SnO4) as front contact, zinc stannate (Zn2SnO4) and zinc oxide (ZnO) as buffer layer and antimony telluride (Sb2Te3) insertion with Nickle (Ni) as back contact has been investigated in the conventional (SnO2/CdS/CdTe/Ag) CdTe cell structures in which CdS is replaced by zinc cadmium sulphide (ZnxCd1−xS) as window layer. Efficiency as high as 18.0% has been found with 80 nm of ZnxCd1−xS window layer for x=0.05, 1 µm of CdTe layer and 100 nm Zn2SnO4 buffer layer without Sb2Te3 back contact. However, ZnO insertion shows low conversion efficiency of 7.84% and 12.26%, respectively with and without Sb2Te3 back contact. It has been found that 1 µm of CdTe absorber layer, 70 nm of ZnxCd1−xS (x=0.05) window layer, 100 nm of Zn2SnO4 buffer layer and 100 nm Sb2Te3 back contact layer are sufficient for high efficiency (>17.5%) ZnxCd1−xS/CdTe cells. Moreover, it was found that the cell normalized efficiency linearly decreases with the increasing operating temperature at the temperature gradient of −0.25%/°C.