The matching of charge transport layer and photoactive layer is critical in solar energy conversion devices, especially for planar perovskite solar cells based on the SnO2 electron‐transfer layer (ETL) owing to its unmatched photogenerated electron and hole extraction rates. Graphdiyne (GDY) with multi‐roles has been incorporated to maximize the matching between SnO2 and perovskite regarding electron extraction rate optimization and interface engineering towards both perovskite crystallization process and subsequent photovoltaic service duration. The GDY doped SnO2 layer has fourfold improved electron mobility due to freshly formed C−O σ bond and more facilitated band alignment. The enhanced hydrophobicity inhibits heterogeneous perovskite nucleation, contributing to a high‐quality film with diminished grain boundaries and lower defect density. Also, the interfacial passivation of Pb−I anti‐site defects has been demonstrated via GDY introduction.

The Lewis acid–base adduct approach has been widely used to form high‐crystalline perovskite films, but the complicated crystallization pathway and underlying film formation mechanism are still ambiguous. Here, the detailed crystallization process of perovskites manipulated by Lewis base additives has been revealed by in situ X‐ray scattering measurements. Through monitoring the film formation process, two distinct crystal growth stages have been definitely recognized: i) an intermediate phase‐dominated stage; and ii) a phase transformation stage from intermediates to crystalline perovskite phase. Incorporating Lewis base additives significantly prolongs the duration of stage 1 and induces a postponed phase transformation pathway, which could be responsible for retardant crystallization kinetics. Based on a series of experimental results and theoretical calculations, it is indicated that the manipulation of perovskite crystallization pathway is a result of the modulated molecular interactions between Lewis base additives and solution precursors. Owing to the retardant crystallization kinetics, enhanced‐quality perovskite films with reduced defect density and improved optoelectronic properties, as well as optimized photovoltaic performance have been demonstrated. This work provides in‐depth understanding with respect to perovskite crystallization pathway modulated by Lewis base additives and perceptive guidelines for precise regulation of crystallization kinetics of perovskite film toward high performance.

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