Spontaneous low-temperature crystallization of α-FAPbI3 for highly efficient perovskite solar cells

• 来源期刊: 科学通报（英文版）
• 年，卷（期）: 2019,（21）
• 页码范围: 1608-1616
• 页数: 9页
• 语种: 英文

摘要

Formamidinium lead triiodide (HC(NH2)2Pbl3 or FAPbI3) is a promising light absorber for high-efficiency perovskite solar cells because of its superior light absorption range and thermal stability to CH3NH3Pbl3 (MAPbI3).Unfortunately,it is difficult to fabricate high-quality FAPbl3 thin films to surpass the MAPbI3-based cells due to easily forming unwanted but more stable yellow 8-phase and thus requiring high annealing-temperature for wanted photovoltaic-active black α-phase.Herein,we reported a novel low-temperature fabrication of highly crystallized α-FAPbI3 film exhibiting uniaxial-oriented nature with large grain sizes up to 2 μm.First-principles energetic calculations predicted that this novel deposition should be ascribed to the formation of a high-energy metastable two-dimensional (2D) intermediate of MAFAPbI3Cl followed by a spontaneous conversion to α-FAPbI3.The ions exchange reaction during this MAFAPbI3Cl-FAPbI3 conversion account for the perovskite film uniaxial-oriented grown along the (1 1 1) direction.This large-grain and uniaxial-oriented grown α-FAPbl3 based solar cells exhibited an efficiency up to 20.4％ accompanying with low density-voltage (J-V) hysteresis and high stability.