Simultaneous Interface Amelioration and Energy Level Modulation Using In Situ Polymerized Molecules for Efficient and Stable Perovskite Solar Cells

Charge accumulation and charged defects at both bulk and buried heterojunction interfaces of perovskites are primarily related to the photovoltaic performance and shelf stability of perovskite solar cells (PSCs). Moreover, detrimental defects distributing along the perovskite bottom side in contact with the tin oxide (SnO2) surface may exert unparalleled significance in charge extraction and transport. Most importantly, interfacial nonradiative recombination can also widely exist, which will seriously hamper efficiency of the related device. In this work, a multifunctional chemical bridge at the perovskite/SnO2 interface is devised through triggering an in situ polymerization strategy, by which cross-linked polymerizable 3-(trimethoxysilyl)-propyl methacrylate (MAPS) monomers under the combination of temperature and initiators can form bulkier macropolymers (MAPS dimers). Detailed theoretical and experimental results reveal that the carbonyl groups (C=O) of both MAPS monomers and MAPS dimers can chemically anchor to perovskite bottom side through a C=O center dot center dot center dot Pb coordination bond interaction to regulate the film quality and the siloxane groups effectively couple with oxygen vacancies on the SnO2 film surface to facilitate its optoelectronic properties. Compared with the primitive MAPS monomer units, the resultant MAPS dimers simultaneously prevent interfacial charge accumulation and demonstrate a more benign energy level alignment to further augment photovoltaic performance of PSCs. Thus, the devices assembled under open-air conditions based on double-sided passivation deliver a decent photoelectronic performance with the champion efficiency of 20.94% accompanied by negligible hysteresis. Meanwhile, the unencapsulated targeted devices maintain 93.1% and 86.5% of their original efficiency after continuous 500 h thermal treatment and 500 h light illumination under open-circuit conditions, respectively.