Organic–inorganic hybrid perovskites are promising materials for optoelectronic applications. Solution-processed films typically possess deleterious randomly oriented grains that limit their potential. Here, we report growth of highly oriented methylammonium lead bromide (MAPbBr₃) films through ion exchange from 2D to 3D perovskite. We first investigate the ion exchange reaction mechanism for conversion between 2D and 3D perovskites using a combined experimental and theoretical approach. The selectivity of conversion is governed by thermodynamics and kinetics of the ion exchange reaction and is intimately linked to the molecular structure of the organic cation in 2D perovskite. Subsequently using the derived insights, we chose phenylethylammonium lead bromide (PEA₂PbBr₄) as the 2D growth template and successfully exchanged it into high-quality 3D MAPbBr₃ films with strong uniaxial 100 orientation. The enhanced film quality leads to ultranarrow electroluminescence spectra (15.3 nm fwhm and 98.10% color purity) and demonstrates the immense potential of the ion exchange method for achieving ultra-high-resolution displays.

中文翻译：

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通过离子交换实现高度取向的MAPbBr ₃钙钛矿薄膜，实现超高色纯度的绿光发射

有机-无机杂化钙钛矿是用于光电应用的有前途的材料。固溶处理的薄膜通常具有有害的随机取向的晶粒，从而限制了其潜力。在这里，我们报道了通过从2D钙钛矿到3D钙钛矿的离子交换，高取向甲基铵溴化铅（MAPbBr ₃）薄膜的生长。我们首先研究结合实验和理论方法在2D和3D钙钛矿之间转化的离子交换反应机理。转化的选择性受离子交换反应的热力学和动力学控制，并与二维钙钛矿中有机阳离子的分子结构密切相关。随后，使用得出的见解，我们选择了苯乙铵溴化铅（PEA ₂ PbBr ₄）作为2D生长模板，并成功地将其交换为具有强单轴100取向的高质量3D MAPbBr ₃薄膜。增强的薄膜质量可导致超窄电致发光光谱（15.3 nm fwhm和98.10％的色纯度），并证明了离子交换方法在实现超高分辨率显示方面的巨大潜力。