Regulating the Crystallization and Carrier Dynamics for High-Performance Quasi-2D Tin Perovskite Solar Cells

Compared with three-dimensional (3D) tin halide perovskite, quasi-two-dimensional (2D) tin halide perovskite shows high stability and low defect density by introducing bulky organic spacers, which is beneficial to realize efficient and stable tin perovskite solar cells (TPSCs). However, the competitive growth between low-dimensional and three-dimensional (3D) structures leads to a complex and uncontrollable crystallization process, thus leading to the random orientation, disordered structure, and poor carrier dynamics in the corresponding devices. Here, we proposed a gradient thermal annealing (GTA) to deposit high-quality tin halide perovskite films with stable structure and low defect density by controlling the crystal growth process. Femtosecond transient absorptions confirmed that this strategy can adjust the growth speed of perovskites with different dimensions, and reduce the proportion of small n -phases which tend to grow parallel to the substrate. This further facilitated the charge transfer and enhanced the charge carrier transport and extraction. As a result, the power conversion efficiency (PCE) of the corresponding quasi-2D (⟨ n ⟩ = 10) Ruddlesden–Popper (RP) TPSCs was increased from 9.14% to 12.05% with strengthened environmental stability. Notably, this approach is also applicable in both RP and Dion-Jacobson (DJ) quasi-2D TPSCs, which provides a method to high efficiency quasi-2D TPSCs by regulating the carrier transport.