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

Cadmium tin oxide (CTO) thin films were deposited by radio frequency (RF) magnetron sputtering from a CdO:SnO2 target onto glass substrates at temperatures from ambient to 300 degrees C. As-deposited films exhibited amorphous structure and high sheet resistance. Single phase cadmium stannate (Cd2SnO4) thin films with cubic spinel structure having both random and preferred orientation along (400) were obtained after annealing in Ar/CdS atmosphere. The randomly-oriented single phase Cd2SnO4 thin films showed a high mobility of >50 cm(2) V (1) s (1) and carrier density of similar to 7 x 10(20) cm (3). The thermal expansion coefficient of Cd2SnO4 films was determined to be 5.6 x 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 Cd2SnO4 films as the window layer. Published by Elsevier B.V.