Functionalized-MXene-nanosheet-doped tin oxide enhances the electrical properties in perovskite solar cells

An appropriate electron transport layer (ETL) with better energy alignment and enhanced charge transfer, thereby helping efficient extraction and transport of photogenerated carriers, is essential to achieve the creation of high-performance devices. In this work, we use functionalized MXene modified with fluoroalkylsilane and dodecyltrimethoxysilane molecules, denoted as SnO2-MF and SnO2-MH, as nanosheet dopants in the SnO2 ETL. From density functional theory (DFT) calculations and ultraviolet photoelectron spectra (UPS) spectra, we see that better band alignment is achieved for the SnO2-MH ETL. Meanwhile, functionalized MXene nanosheets represent high electrical conductivity and mobility and could form zero Schottky barrier heterojunction with SnO2, effectively and rapidly enhancing carrier transfer. Finally, the suitable surface energy achieved by functionalized MXene additives can enlarge the grain size of perovskite thin films. Consequently, a significant improvement of power conversion efficiency (PCE) from 20.98% to 23.66% (24.12% for the champion device with a fill factor [FF] over 0.84) can be achieved for devices based on the SnO2-MH ETL, which also possess improved moisture resistance and operational stability.