Co-assembly of monolayers through π-π interactions for efficient inverted perovskite solar modules

The integration of NiOx and self-assembled monolayers (SAMs) as a co-hole transport layer (HTL) is currently a primary approach to achieving high-efficiency perovskite solar cells (PSCs). However, the strong tendency for self-aggregation and the poor wettability of the SAMs can result in significant charge carrier losses at the interface, hindering further improvements in PSC efficiency and stability. To tackle these issues, we employ a strategy of co-assembling [4-(3,6- dimethyl-9H-carbazol-9-yl)butyl]phosphonic acid (Me-4PACz) with 2,6-difluoro-3-nitrobenzonitrile (DN) through π-π interactions, which effectively reduces the self-aggregation of Me-4PACz and enhances the wettability. This improvement leads to an increase in the perovskite crystalline quality, suppresses carrier recombination at the interface, and accelerates hole extraction and transport. As a result, the perovskite solar module (PSM) based on the DN-Me (effective area 57.3 cm²) attains an efficiency of 20.23%. Furthermore, the encapsulated PSM can maintain 95% of its original efficiency following 1000 hours of continuous testing under 1-sun illumination.