Directional Crystallization by Floating Self-Assembly for Efficient and Stable Tin-based Perovskite Solar Cells

Tin-based perovskite materials have attracted intensive research due to its environmental friendliness and tremendous potential in the photovoltaic field. However, the extremely poor crystalline quality and awful stability of tin-based perovskite have restricted the further improvement in optoelectronic performance. Herein, a novel strategy of crystal orientate manipulation is proposed by introducing a self-assembly molecule, fluorinated-perylene diimide (F-PDI), which provides an external driving force to guide the orientated crystallization of perovskite in the vertical direction, and thus greatly promotes the effective transmission of carriers. The conductive F-PDI simultaneously serves as defect passivator and hydrophobic barrier layer, which boosts the photoelectric performance and contributes to the lattice robustness. As a result, the unencapsulated device based on F-PDI achieves considerable power conversion efficiency (PCE) of 9.49% and exhibits remarkable long-term stability, maintaining over 80% of its original efficiency after ∼3000 h storage under light soaking.