Effect of Ga incorporation in sequentially prepared CuInS sub(2) thin film absorbers

Thin film CuInS sub(2):Ga solar cell absorber films were prepared by sequential evaporation of Cu-In-Ga precursors and sulfurization in sulfur vapor. The depth distribution of Ga was found to be highly inhomogeneous caused by CuGaS sub(2) phase segregation at the back contact. Depending on overall Ga content and sulfurization temperature a quaternary CuGa sub(x)In sub(1-x)S sub(2) compound formed exhibiting a shift in absorber lattice constant and band gap. Micro Raman measurements showed that crystal quality was also affected by Ga. Open-circuit voltages well above 800 mV were achieved while sustaining high fill factors of 71%.