Two-Dimensional Tin-Based Chiral Perovskites with a High Degree of Circularly Polarized Luminescence

Two-dimensional (2D) hybrid organic–inorganic halide perovskites have garnered increasing attention due to their unique physical properties and potential applications in optoelectronic devices. Introducing chiral organic ligands into layered inorganic frameworks can impart strong chirality to pure 2D perovskites, offering the potential for applications in circularly polarized light emission and detection. However, most of them are lead-based chiral perovskites, which inherit the toxicity of lead. To overcome the toxicity limitations, lead-free chiral perovskites have been developed by using manganese (Mn), copper (Cu), bismuth (Bi), and tin (Sn). Among these alternatives, tin (Sn) has emerged as the most promising candidate because tin and lead both have similar ionic radii and valence electron structures. Nevertheless, the study of 2D tin-based chiral perovskite is still in fancy. Here, we report a new two-dimensional tin-based chiral perovskite (S-/R-3BrMBA)2SnI4 [3BrMBA = 1-(3-bromphenyl)-ethylamine] with a high degree of circularly polarized light emission. The as-synthesized 2D tin-based chiral perovskite (S-3BrMBA)2SnI4 shows an average (maximum) degree of circular polarization (DOCP) of 26.2% (35.8%) at 78 K, which is the highest value in lead-free chiral perovskites reported to date and might be ascribed to the large lattice distortion induced by the chiral ligands. The DOCP decreases with increasing temperature and maintains a constant value with the excitation power. The high DOCP in our pure chiral 2D perovskites would shed light on the development and exploration of lead-free spin-associated optoelectronic devices.

二维（2D）有机-无机杂化卤化物钙钛矿（two-dimensional (2D) hybrid organic–inorganic halide perovskites）因其独特的物理特性以及在光电器件中的潜在应用而受到日益广泛的关注。将手性有机配体引入层状无机骨架中，可使纯二维钙钛矿获得显著手性，为其在圆偏振光发射与探测领域的应用提供可能。然而，当前多数此类材料为含铅手性钙钛矿，继承了铅的毒性。为克服毒性限制，研究人员已通过使用锰（Mn）、铜（Cu）、铋（Bi）和锡（Sn）开发出无铅手性钙钛矿。在这些替代材料中，锡（Sn）已成为最具潜力的候选者，这是因为锡与铅具有相似的离子半径与价电子结构。然而，二维锡基手性钙钛矿的相关研究仍处于起步阶段。本工作报道了一种新型二维锡基手性钙钛矿(S-/R-3BrMBA)2SnI4 [3BrMBA=1-(3-溴苯基)乙胺]，其展现出优异的圆偏振光发射特性。合成得到的二维锡基手性钙钛矿(S-3BrMBA)2SnI4在78 K下的平均（最大）圆偏振度（degree of circular polarization, DOCP）可达26.2%（35.8%），这是目前已报道的无铅手性钙钛矿中的最高值，该性能可归因于手性配体诱导的显著晶格畸变。圆偏振度随温度升高而降低，但在不同激发功率下保持稳定。本研究中纯手性二维钙钛矿所展现的高圆偏振度，将为无铅自旋相关光电器件的开发与探索提供新思路。