Optimization of ITO layers for applications in a-Si/c-Si heterojunction solar cells

A detailed study of the properties of indium tin oxide (ITO) thin films used as antireflecting front electrodes in a-Si/c-Si heterojunction solar cells is presented. The deposition conditions of ITO layers by radiofrequency magnetron sputtering were optimized for heterojunction solar cells applications. The X-ray photoelectron spectroscopy analysis of the deposited films allowed for a correlation between the film composition and the experimental parameters used in the sputtering process. The ITO thickness was optimized considering the thickness of the a-Si emitter layer, its optical characteristics and the heterojunction solar cell spectral response. In our devices, the optimal thickness calculated for the ITO film was in the range 80–95 nm, depending on the solar cell spectral response, and a thickness tolerance of ±10 nm was found to be suitable to limit the degradation of the device performance. Finally, device simulation results obtained by the ‘Analysis of Microelectronic and Photonic Structures’ code are reported.