Do T Thu Ha, Granados Del Águila Andrés, Xing Jun, Liu Sheng, Xiong Qihua
Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371.
Key Laboratory of Eco-Chemical Engineering, Ministry of Education, Qingdao University of Science and Technology, Qingdao 266042, China.
J Chem Phys. 2020 Aug 14;153(6):064705. doi: 10.1063/5.0012307.
Atomically thin layers of two-dimensional lead halide perovskite semiconductors exhibit prominent light emission due to the inherently strong quantum and dielectric confinement. Electronic band structures and coupled electron-hole pairs (excitons), which govern the optical properties, are not well understood in these emergent two-dimensional materials. Here, we have performed both the steady-state and time-resolved photoluminescence spectroscopies with varying temperature to study the optical responses of a high-quality (PEA)PbI single crystal. We observe a multitude of exciton transitions with different responses to temperature that suggests their different origins. Furthermore, our results suggest that the photoluminescence of layered perovskites is dominated by direct exciton transitions at low temperatures, while by an indirect exciton at high temperatures that can be explained by our proposed exciton band structure incorporating the interplay of Coulomb and Rashba effects. Our study sheds light on the intrinsic optical properties of two-dimensional perovskites that may be beneficial for the novel applications of perovskite-based devices.
由于固有的强量子和介电限制，二维卤化铅钙钛矿半导体的原子级薄层表现出显著的光发射。在这些新兴的二维材料中，决定光学性质的电子能带结构和耦合的电子 - 空穴对（激子）尚未得到很好的理解。在这里，我们进行了变温稳态和时间分辨光致发光光谱研究，以研究高质量（PEA）PbI单晶的光学响应。我们观察到大量对温度有不同响应的激子跃迁，这表明它们有不同的起源。此外，我们的结果表明，层状钙钛矿的光致发光在低温下由直接激子跃迁主导，而在高温下由间接激子主导，这可以通过我们提出的包含库仑和 Rashba 效应相互作用的激子能带结构来解释。我们的研究揭示了二维钙钛矿的固有光学性质，这可能有利于基于钙钛矿的器件的新应用。
