Hybrid organic–inorganic lead halide perovskites have shown promising results as active layers in light-emitting diodes, typically utilizing the near-monochromatic, free exciton emission. Some perovskite compounds, however, show broad-band emission that is more intense than the free exciton counterpart. In this study, we show that the light emission properties of Ruddlesden–Popper hybrid perovskites PEA₂MA_n–1Pb_nI_3n+1 (PEA = phenethylammonium, MA = methylammonium) can be tuned by Sn alloying and are highly sensitive to Sn %. With increasing dimensionality, the broad-band emission quantum yield decreases drastically, from 23% in n = 1 to <1% for the n = 3 compound. Using density functional theory calculations and transient reflectance spectroscopy, the broad emission is identified as originating from self-trapped excitons. A dynamic picture of the formation process is also presented, for which ultrafast (<5 ps) hole-trapping at the Sn site is the first step, followed by electron localization from Coulombic interaction. These findings are especially valuable for designing perovskite materials with intense room-temperature broad-band emission for solid-state lighting applications.

中文翻译：

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锡合金Ruddlesden-Pop杂化碘化物钙钛矿中宽带发射的起源和结构尺寸的影响

混合的有机-无机卤化铅钙钛矿已显示出令人鼓舞的结果，它们通常用作发光二极管中的活性层，通常利用接近单色的自由激子发射。但是，某些钙钛矿化合物显示的宽带发射比自由激子对应物的发射强度更高。在这项研究中，我们表明Ruddlesden-Popper杂化钙钛矿PEA ₂ MA _{n –1} Pb _n I _{3 n +1}（PEA =苯乙铵，MA =甲基铵）的发光特性可以通过Sn合金来调节，并且对Sn高度敏感。锡％随着维数的宽带发光量子产率急剧下降，从23％Ñ = 1至<1％为Ñ= 3复合。使用密度泛函理论计算和瞬态反射光谱，可将宽发射确定为源自自陷激子。还提供了形成过程的动态图片，为此第一步是在Sn位置进行超快（<5 ps）空穴俘获，然后是来自库仑相互作用的电子局部化。这些发现对于设计用于固态照明应用的具有强烈室温宽带发射的钙钛矿材料特别有价值。