Buried interfacial modification in inverted perovskite solar cells with mercaptoethylamine

Poly (bis (4-phenyl) (2,4, 6-trimethylamine) amine) (PTAA) is widely used as a hole transport layer (HTL) in inverted perovskite solar cells (PSCs). However, the high hydrophobicity and non-radiative recombination losses of PTAA greatly limit the repeatability and photoelectric performance of PSCs. In this study, mercaptoethylamine (MEA), containing sulfhydryl groups, is proposed to fill the interface defect between PTAA and the perovskite layer, significantly improving the wettability of PTAA film and resulting in a more uniform perovskite layer deposition when compared with the common short carbon chain, propylamine (PA). By evaluating the energy level alignment and perovskite crystal growth in CsFA-based PSCs, it is demonstrated that MEA effectively eliminates lead (Pb) defects at the buried interface of perovskite films, suppresses trap-assisted carrier recombination, and extends the operational lifespan of PSCs. The results show that the power conversion efficiency of the p-i-n inverted CsFA-based photovoltaic device, reaches 22% after MEA optimization, and the unpackaged device maintains 97% of its initial efficiency under standard illumination after 300 h. Furthermore, when MEA was introduced to optimize the buried interface of CsFAMA-based perovskite films, the device achieved a power conversion efficiency of 23.18%. This work provides a promising approach for improving the performance and stability of perovskite solar cells through organic cation modification at the PTAA/perovskite interface.