Electrical characterization and defect states analysis of Ag/ITO/MoO_x/n-Si/LiF_x/Al carrier selective contact solar cells processed at room-temperature

摘要

Carrier-selective contact based silicon heterojunction solar cell of Ag/ITO/MoO_x/n-Si/LiF_x/Al is fabricated at room-temperature, having a power conversion efficiency of >15% without using any silicon surface passivation layer. For device fabrication; molybdenum oxide (MoO_x) and lithium fluoride (LiF_x) are used as hole- and electron-selective thin layers on low-cost industrially feasible Cz n-type silicon wafers, respectively. The device characteristics are investigated by dark/light current density-voltage, quantum efficiency, and capacitance-voltage measurements, and also MoO_x/n-Si interface states density by admittance spectroscopy. The performance of cell is found to be limited by the detrimental interface defect states at the MoO_x/n-Si interface (～2×10~(12) eV~(-1) cm~(-2)), and also high n-Si/LiF_x back-surface recombination that is reflected in quantum efficiency response in the longer wavelength region (800 nm to 1100 nm). Small built-in-potential of ～0.69 V at the MoO_x/n-Si interface is observed from the Mott-Schottky plot, which is led to the open-circuit voltage of device to ～0.57 V. The absence of strong inversion layer is due to the presence of large number of interface defect states at the MoO_x/n-Si junction, and reverse saturation current density of ～4.1×10~(-8) A/cm~2.