Room-Temperature Electron-Selective Passivating Contact with Titanium-Peroxo Complexes for High-Efficiency Silicon Solar Cells

Abstract

The increasing demand for high-performance and cost-effective solar cells is the driving factor in the development of new nanomaterials or compounds compatible with low-cost, low-temperature fabrication routes. Titanium oxide (TiOx), an inexpensive earth-abundant material, is among the most extensively investigated candidates for electron-selective layer in silicon solar cells. In this study, we present a facile and innovative synthesis approach to enhance the electrical performance of solution-processed TiOx layer through the formation of titanium-peroxo (Ti-OO) compound via hydrogen peroxide (H2O2) modification. Owing to this modification an outstanding implied open-circuit voltage (iVoc) of 713 mV and a low contact resistivity (ρc) of 1.96 mΩ cm² are achieved simultaneously. At the device level, the highest power conversion efficiency (PCE) of 21.9 % is measured for cells with modified-TiOx/LiFx/Al electron-selective passivating contact (ESPC). Notably, this record efficiency is attained using a dopant-free standalone TiOx electron-selective passivating layer produced at room temperature, without requiring any annealing steps throughout the fabrication process. Experimental characterizations consolidate the formation of Ti-OO complex upon H2O2 modification and reveal the subsequent changes in the structural and electrochemical properties of the TiOx layer. The reduced work function (WF) at n-Si/TiOx heterojunction is identified as the key factor responsible for the enhanced surface passivation quality and electron-selectivity characteristics of the proposed TiOx layer. The accomplishments outlined in this study open new avenues for advancing high-efficiency crystalline silicon (c-Si) solar cells through a simplified fabrication process.