Crystal growth, defect passivation and strain release via In-situ Self-polymerization strategy enables efficient and stable perovskite solar cells.

We demonstrate an in-situ self-polymerization (ISP) strategy to prepare high-quality FA x MA 1- x PbI 3 films, which achieves the triple functions of grain growth, defect passivation and strain release. The corresponding PSCs delivers an efficiency of 22.9% and superior long-term stability. [Display omitted] • High-quality perovskite film is prepared by in-situ self-polymerization strategy. • The ISP strategy allows relaxation of tensile strain by 34% for perovskite film. • The optimized device achieves a champion PCE of 22.9%. • The storage and thermal stability of the device are greatly improved. The perovskite film fabricated by the currently approbatory solution method with high temperature annealing process is inevitably accompanied by the defects and strains, which are two critical factors affecting the photovoltaic performance of perovskite solar cells (PSCs). Herein, we demonstrate an in-situ self-polymerization (ISP) strategy for high-performance PSCs by incorporating self-polymerizable n-methacrylamide (NMA) monomer additives into the perovskite film. It is revealed that NMA could not only regulate crystal growth, but also passivate grain boundary defects through its own carbonyl groups. Moreover, the self-polymerization of NMA monomer could confine the thermal-expansion of perovskite during thermal crystallization process, thereby releasing the tensile strain of perovskite film. As a result, the optimized devices achieve a champion power conversion efficiency (PCE) of 22.9%. These unencapsulated devices could maintain 91% of their initial PCE after aging 1500 h in ambient air (25 ± 5 ℃, 30 ± 5% relative humidity, dark) and 85% efficiency after annealing 600 h at 65 ℃ in nitrogen atmosphere. [ABSTRACT FROM AUTHOR]