Back Contact Materials for Superstrate CuInS2 Solar Cells

CuInS2 (CIS) solar cells were fabricated by spray pyrolysis method with different back contact electrodes of Al, Cu, Mo, Au, and C (carbon). The best conversion efficiencies of CuInS2 cells using Al, Cu, Mo, Au, and C back contacts were 1.96%, 2.17%, 2.08%, 1.87%, and 2.35%, respectively. The conversion efficiency of the cells using Al and Cu back contacts significantly deteriorated after one month keeping devices in air ambience. The device performance of the CIS cells using Au, Mo and Carbon is quite stable after one month. The effect of back contact on each photovoltaic parameter has been confirmed by impedance measurements. Carbon films were crack- free and showed adequate adhesion with the CuInS2 absorber layer. The annealing temperature for carbon films is in the range of 125- 240 °C. The cell parameters of the CIS cells using carbon back contact are Jsc = 10.36 mA/cm2, Voc = 0.50 V, fill factor = 0.44 and conversion efficiency = 2.35%. The resulting CIS solar cells, fabricated by spray-pyrolysis depositions for CIS layers and screen printings for carbon layers, are recognized as full non-vacuum fabricated solar cells.