High-Efficiency Sb2(S,Se)3 Solar Cells with New Hole Transport Layer-Free Back Architecture via 2D Titanium-Carbide Mxene

MXene, a class of 2D materials of metal carbide or nitride, has attracted a lot of attention recently due to its excellent optical and electrical properties. In this work, titanium-carbide MXene (Ti 3 C 2 T x ) is introduced as a back electrode in Sb 2 (S,Se) 3 thin-film solar cells (FTO/CdS/Sb 2 (S,Se) 3 /MXene) for the first time, which displaces traditional carbon (C) and gold (Au) electrodes entirely. Impressively, thanks to its high conductivity, mild reflectivity, and flexible flake architecture, the MXene-based device performance outperforms typical C and Au electrodes by 153% and 77%, respectively. Specifically, the tunable work function of MXene and a beneficial Sb–O bond formed between Sb 2 (S,Se) 3 and MXene efficiently suppress the recombination and enhance charge transport by enjoying the unique merit of the rich terminal groups of MXene. As a result, the best efficiency of 8.29% of MXene-based Sb 2 (S,Se) 3 solar device is achieved, which represents the highest performance of noble metal and/or hole transport layer-free derived Sb 2 (S,Se) 3 solar cells to date. This result has revealed that MXene is a feasible material to substitute the back electrode in Sb-based solar cells to reach high efficiency, low cost, and high stability.