Effect of ITO capping and its deposition parameters on electrical properties of MoO3/Si carrier-selective contact solar cell

Abstract

Silicon solar cells with heterojunction carrier-selective contact are fabricated using molybdenum trioxide for passivation and hole selectivity. No additional thin intrinsic a-Si:H layer passivation is used in any of the experiment. The MoO3/Si heterojunction showed diode behaviour but it degraded in ambient conditions. Deposition of tin-doped indium oxide (ITO) over-layer well protected the device from degradation. However, the deposition parameters of ITO layer greatly influenced electrical properties of MoO3/Si device. The MoO3–ITO interface properties strongly depend upon ITO deposition parameters such as sputter power and substrate temperature. This dependence influences particularly the series resistance and hence, fill factor. With optimization of ITO deposition parameters and metal contact annealing, we could double the fill factor of our cells. Using these optimized conditions, a double heterojunction test cell structure is made using titanium dioxide as electron selective layer. This MoO3/Si/TiO2 solar cell reached JSC of 27.3 mA/cm2, VOC of 530 mV and active area efficiency of 7.86% under 1 Sun simulated radiation. Recently, we have achieved JSC exceeding 30 mA/cm2 and VOC exceeding 600 mV for our reference cells. This a-Si-free approach offers low thermal as well as low overall budget crystalline silicon-based solar cell fabrication route.