Indium tin oxide thin films by bias magnetron rf sputtering for heterojunction solar cells application

In this investigation ITO thin films were prepared by bias magnetron rf sputtering technique at substrate temperature of 180 °C and low substrate-target distance for future a-Si:H/c-Si heterojunction (HJ) solar cells application. Microstructure, surface morphology, electrical and optical properties of these films were characterized and analyzed. The effects of ion bombardments on growing ITO films are well discussed. XRD analysis revealed a change in preferential orientation of polycrystalline structure from (2 2 2) to (4 0 0) plane with the increase of negative bias voltage. Textured surface were observed on AFM graphs of samples prepared at high negative bias. Hall measurements showed that the carrier density and Hall mobility of these ITO films are sensitive to the bias voltage applied. We attributed these effects to the sensitivity of energy of Ar⁺ ions bombarding on growing films to the applied bias voltage in our experiments. At last the figure of merit was calculated to evaluate the quality of ITO thin films, the results of which show that sample prepared at bias voltage of −75 V is good to be used in HJ cells application.