Cadmium tin oxide thin films deposited by RF magnetron sputtering for photovoltaic applications

Abstract Cadmium tin oxide (CTO) thin films were deposited by radio frequency (RF) magnetron sputtering from a CdO:SnO 2 target onto glass substrates at temperatures from ambient to 300 °C. As-deposited films exhibited amorphous structure and high sheet resistance. Single phase cadmium stannate (Cd 2 SnO 4 ) thin films with cubic spinel structure having both random and preferred orientation along (4 0 0) were obtained after annealing in Ar/CdS atmosphere. The randomly-oriented single phase Cd 2 SnO 4 thin films showed a high mobility of >50 cm 2  V −1  s −1 and carrier density of ∼7 × 10 20  cm −3 . The thermal expansion coefficient of Cd 2 SnO 4 films was determined to be 5.6 × 10 −6  cm/cm/K. The dependence of optical and electrical properties of the as-deposited and annealed CTO thin films on oxygen content in the sputtering gas, substrate temperature and annealing temperature were reported. 16% (AM 1.5) conversion efficiency was achieved for CdTe thin film solar cells using Cd 2 SnO 4 films as the window layer.