While (100) facet-dominated FAPbI₃ perovskite films have been readily obtained, (111) facet-dominated ones with higher potential for preventing moisture-induced δ-phase transition are hardly achieved. Particularly, growth kinetics of the (111) facet remains elusive. We herein report (111) facet-dominated perovskite films fabricated via a two-step method by incorporating organic ammonium salts (OASs) into the PbI₂ precursor solution and reveal the underlying facet growth mechanism. The cation of the OAS with a larger size than FA⁺, intercalated into interlayers of PbI₂ in the first step, hinders the insertion of FA⁺ into (100) facet-exposed crystals in the second step, thus inhibiting the growth of (100) facets. In contrast, (111) facets can grow without interference because FA⁺ is located on the external layer, enabling their more favorable growth than that of (100) facets. Moreover, the anion of the OAS retarding perovskite growth prolongs the inhibition of (100) facets, continuously increasing the fraction of (111) facets. The resultant perovskite films dominated by (111) facets with ordered stacking along the out-of-plane direction offer a solar-cell efficiency of 25.23% with improved stability compared to those with mixed (111) and (100) facets. This work provides an effective strategy to obtain highly (111) facet-oriented perovskite films and elucidates additive-engineered growth kinetics.

中文翻译：

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钙钛矿薄膜中具有有序堆叠的主导 (111) 面


虽然（100）面主导的 FAPbI ₃ 钙钛矿薄膜很容易获得，但（111）面主导的钙钛矿薄膜却难以实现，该薄膜具有更高的防止水分诱导的 δ 相变的潜力。特别是（111）面的生长动力学仍然难以捉摸。我们在此报道了通过将有机铵盐（OAS）掺入 PbI ₂ 前驱体溶液中，通过两步法制备的（111）晶面主导的钙钛矿薄膜，并揭示了潜在的晶面生长机制。尺寸大于 FA ⁺ 的 OAS 阳离子在第一步中插入 PbI ₂ 的层间，阻碍了 FA ⁺ 插入 (在第二步中，100）晶面暴露晶体，从而抑制（100）晶面的生长。相反，(111)面可以不受干扰地生长，因为FA ⁺ 位于外层，使其比(100)面更有利地生长。此外，OAS的阴离子阻碍钙钛矿生长，延长了(100)晶面的抑制，持续增加(111)晶面的比例。与混合(111)和(100)面的钙钛矿薄膜相比，所得钙钛矿薄膜以(111)面为主，沿面外方向有序堆叠，太阳能电池效率为25.23%，稳定性更高。这项工作提供了一种获得高度（111）面取向的钙钛矿薄膜的有效策略，并阐明了增材工程的生长动力学。