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 Zn_xCd_1-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 (Zn_xCd_1-xS) as window layer. Efficiency as high as 18.0% has been found with 80 nm of Zn_xCd_1-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 Zn_xCd_1-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%) Zn_xCd_1-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.