Formamidinium (FA)-based perovskite materials show an extended absorption spectrum to 840 nm, which enables high power conversion efficiencies of over 20% compared with normal-structure perovskite solar cells (PSCs). However, it is rarely possible to obtain high performance in inverted-structure PSCs owing to the unbalanced electron–hole transport properties. To achieve desirable electronic qualities in a FA perovskite film, it is necessary to substantially improve the crystallinity of the perovskite films. A new perovskite growth method is presented here using methylammonium chloride (MACl) to assist vertical recrystallization in a formamidinium perovskite film. The obtained film consists of highly crystallized vertically-orientated grains, which minimize the vertical grain boundary and trap site in the films, and later contribute to a power conversion efficiency above 20% in inverted-structure PSCs. Most importantly, the highly crystalline, phase-pure morphology and low MA content in formamidinium perovskite films can contribute to the light-soaking stability and thermal stability up to 500 h in solar-cell devices.

中文翻译：

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垂直重结晶，可实现高效，稳定的基于甲ami的倒置结构钙钛矿太阳能电池

基于甲酰胺基（FA）的钙钛矿材料显示了一个扩展到840 nm的吸收光谱，与普通结构的钙钛矿太阳能电池（PSC）相比，实现了超过20％的高功率转换效率。但是，由于电子-空穴传输特性的不平衡，在倒置结构的PSC中几乎不可能获得高性能。为了在FA钙钛矿膜中获得期望的电子品质，必须充分改善钙钛矿膜的结晶度。本文介绍了一种新的钙钛矿生长方法，该方法使用甲基氯化铵（MACl）来辅助甲ami钙钛矿膜中的垂直重结晶。所获得的薄膜由高度结晶的垂直取向晶粒组成，这些晶粒可最大程度地减少薄膜中的垂直晶粒边界和陷阱部位，后来又为倒置结构的PSC提供了20％以上的功率转换效率。最重要的是，高钙钛矿型钙钛矿膜中的高度结晶，纯相形态和低MA含量可有助于在太阳能电池装置中长达500小时的光吸收稳定性和热稳定性。