Co-Self-Assembled Interface Engineering Assisted for Bend-Resistant and Efficient Flexible Perovskite Solar Cells

Flexible perovskite solar cells (F-PSCs) have attracted considerable interest for their superior mechanical flexibility. Nonetheless, cryptic bottom-interface defects hinder further improvements in device performance. Here, a co-self-assembled monolayer (Co-SAM) engineering strategy is implemented by integrating 4-nitrophenyl phosphate (PNPP) into [4-(3,6-dimethyl-9H-carbazol-9-yl) butyl] phosphonic acid (Me-4PACz) to improve the NiO_x/perovskite (PVK) interface. This technique enhanced the surface uniformity and hydrophilic nature of the NiO_x/Me-4PACz, while promoting favorable growth of PVK crystal orientation. Furthermore, the PNPP effectively mitigates the generation of defects at the NiO_x surface and the underlying PVK, ultimately significantly improving the interfacial charge transfer efficiency. Consequently, the efficiency of F-PSCs rose from 21.46% to 23.66%. Due to better stress distribution within the PVK and stronger adhesion at the NiO_x/PVK boundary, the F-PSCs retained 80% of their original efficiency even after undergoing 10 000 bending cycles. Notably, PNPP exhibited an outstanding capacity to capture PbI₂, contributing to the potential for reducing Pb leakage of the device under operational conditions.