Efficiency enhancement of TiOx electron-transporting layer-based ultrathin p-type c-Si solar cell by reactive sputtering of backside MoOx hole-transporting contact

Abstract

The importance of efficient carrier selective transport at the backside contact significantly increases with thickness reduction of c-Si solar cells. Here, MoOx backside hole-transporting layer is fabricated on TiOx electron-transporting layer-based ultrathin c-Si solar cell with a final configuration of Ag/ITO/Mg/TiOx/45 μm p-type c-Si/MoOx/Ag by reactive magnetron sputtering method at room temperature. The effects of oxygen ratio and sputtering power on the film phase, bandgap, and surface roughness are investigated. Moreover, the contact performance between Ag and p-type c-Si is systematically studied and optimized by MoOx insertion. Based on the optimized MoOx thin film, the obtained totally dopant-free cell shows an enhancement of all cell parameters with a resultant high efficiency of 12.81%, which is about 12.8% relatively higher than that of conventional backside p+-based one (11.36%). In the combination of experiment and simulation processes, better performance of MoOx-based cell can be ascribed to the improvement of both electrical and optical performances of the device. The realization of MoOx-based contact at room temperature enables the solar cell fabrication under planar state possible, which can greatly avoid the bowing effect and reduce the yield losses and energy consumption during the fabrication of ultrathin c-Si solar cells.