Local Energy Landscape Drives Long-Range Exciton Diffusion in Two-Dimensional Halide Perovskite Semiconductors.
Local Energy Landscape Drives Long-Range Exciton Diffusion in Two-Dimensional Halide Perovskite Semiconductors.
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DOI：
10.1021/acs.jpclett.1c00823
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发表时间：
2021-04-29
期刊：
影响因子：
--
通讯作者：
Stranks SD
中科院分区：
文献类型：
--
作者：
Baldwin A;Delport G;Leng K;Chahbazian R;Galkowski K;Loh KP;Stranks SD
卤化物钙钛矿是多功能半导体，应用包括光伏和发光器件，具有模块化光电特性，可通过组成和维度调整实现。层状Ruddlesden-Popper钙钛矿由于其独特的二维特性和载流子动力学而特别有趣。然而，在这些材料中，通过激子扩散的远程能量传递尚未被理解或实现。在这里，局部时间分辨发光作图技术被用于可视化BA2MAn-1PbnI3n +1钙钛矿家族剥离薄片中的激子传输。根据温度范围的不同，揭示了两种不同的传输机制。在100k以上，扩散是由局域态之间的热激活跳变过程介导的。在较低的温度下，一种不均匀的能量格局出现了，在这种格局中，输运主要是向下的能量转移到较低的能量状态，导致数百纳米的远程输运。高效、远程、可切换的下坡传输为这些2D材料的新应用提供了可控定向远程传输的可能性。
Halide perovskites are versatile semiconductors with applications including photovoltaics and light-emitting devices, having modular optoelectronic properties realizable through composition and dimensionality tuning. Layered Ruddlesden–Popper perovskites are particularly interesting due to their unique 2D character and charge carrier dynamics. However, long-range energy transport through exciton diffusion in these materials is not understood or realized. Here, local time-resolved luminescence mapping techniques are employed to visualize exciton transport in exfoliated flakes of the BA2MAn–1PbnI3n+1 perovskite family. Two distinct transport regimes are uncovered, depending on the temperature range. Above 100 K, diffusion is mediated by thermally activated hopping processes between localized states. At lower temperatures, a nonuniform energy landscape emerges in which transport is dominated by downhill energy transfer to lower-energy states, leading to long-range transport over hundreds of nanometers. Efficient, long-range, and switchable downhill transfer offers exciting possibilities for controlled directional long-range transport in these 2D materials for new applications.
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