Prospects of novel front and back contacts for high efficiency cadmium telluride thin film solar cells from numerical analysis

Cadmium telluride (CdTe) thin film solar cell has long been recognized as a leading photovoltaic candidate for its high efficiency and low cost. A numerical simulation has been performed using AMPS-1D simulator to explore the possibility of higher efficiency and stable CdS/CdTe cell among several cell structures with indium tin oxide (ITO) and cadmium stannate (Cd2SnO4) as front contact material, tin oxide (SnO2), zinc oxide (ZnO) and zinc stannate (Zn2SnO4) as buffer layer, and silver (Ag) or antimony telluride (Sb2Te3) with molybdenum (Mo) or zinc telluride (ZnTe) with aluminium (Al) as back contact material. The cell structure ITO/i-ZnO/CdS/CdSxTe1−x/CdTe/Ag has shown the best conversion efficiency of 16.9% (Voc=0.9 V, Jsc=26.35 mA/cm2, FF=0.783). This analysis has shown that ITO as front contact material, ZnO as buffer layer and ZnTe or Sb2Te3 back surface reflector (BSR) are suitable material system for high efficiency (>15%) and stable CdS/CdTe cells. The cell normalized efficiency linearly decreased at a temperature gradient of −0.25%/°C for ZnTe based cells, and at −0.40%/°C for other cells.