Formamidinium (FA)‐based perovskites exhibit great potential for photovoltaics since they enable the achievement of power conversion efficiency (PCE) over 22%. The bandgap of FA‐based perovskite is lower than that of the methylammonium‐based one, while the larger ionic radius and dual‐ammonia group of FA ions restrain their movement in close‐packing [PbI₆]⁴⁻ cages, leading to improved stability. Here, the structure and properties of FAPbI₃₋ and FA‐based mixed cation perovkites are discussed. In particular, the issues of polymorphism and stabilization of the desired low‐bandgap crystal phase of FAPbI₃ are considered. FAPbI₃ exhibits polymorphisms with a photovoltaically unfavorable δ‐phase that is stable at room temperature, and, thus, it is difficult to prepare continuous and compact FAPbI₃ with the desired crystal structure, namely, the pure α‐phase. Hence, overcoming the limitations of phase transitions is the critical issue in obtaining high‐quality FA‐based perovskite films, which are a prerequisite for solar cells with high PCEs. Here, the focus is on the fabrication methods of FA‐based perovskite films, namely, additive engineering, intermolecular exchange, interfacial engineering, and chemical vapor deposition. A comprehensive overview of the fabrication methodology for the FA‐based perovskite films is provided to facilitate understanding of the underlying mechanisms.

中文翻译：

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基于甲ami的卤化铅钙钛矿：结构，性质和制造方法

基于甲ami（FA）的钙钛矿具有巨大的光电潜力，因为它们可使功率转换效率（PCE）达到22％以上。FA基钙钛矿的带隙小于甲基铵基钙钛矿的带隙，而较大的离子半径和FA离子的双氨基团限制了它们在密排[PbI ₆ ] ^4-笼中的运动，从而提高了稳定性。在此，我们讨论了FAPbI _3-和基于FA的混合阳离子过氧化物的结构和性质。尤其要考虑多态性和FAPbI ₃所需的低带隙晶相的稳定性问题。FAPbI ₃表现出多态性，其光伏相不利于δ相，该相在室温下稳定，因此，很难制备出具有所需晶体结构的连续且致密的FAPbI ₃，即纯α相。因此，克服相变的局限性是获得高质量基于FA的钙钛矿膜的关键问题，这是具有高PCE的太阳能电池的先决条件。在这里，重点是基于FA的钙钛矿薄膜的制造方法，即添加剂工程，分子间交换，界面工程和化学气相沉积。对基于FA的钙钛矿薄膜的制造方法进行了全面概述，以促进对基本机理的理解。