Singh Rachna, Singh Ajeet, Kumar Shubham, Sapra Sameer
Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India.
Nano Lett. 2024 Jun 5;24(22):6797-6804. doi: 10.1021/acs.nanolett.4c01550. Epub 2024 May 22.
It is a huge challenge to increase the photoluminescence (PL) of lead-free halide perovskites, and understanding the mechanism behind exciton dynamics can provide a valuable solution. Herein, we achieved enhanced broad-band emission at ambient conditions in CsAgInCl by tuning self-trapped excitons (STEs) through Al doping. Cryogenic measurements showed an inhomogeneous nature of STE emission due to the presence of defect states and is subject to thermal quenching. An increased Huang-Rhys factor (-factor) resulted in better electron-phonon coupling and high-density STE states post Al doping. Femtosecond transient absorption (fs-TA) results provided insights into the distribution dynamics of excitons, which occurs through gradient energy levels from free excitons (FE) to STEs, where each STE state potentially possesses higher quantized energy states. Overall, this study aims to comprehend the origins of self-trapping and decay of STEs in CsAgInCl:Al and emphasizes the potential of compositional engineering to mitigate self-trapping in this material.
提高无铅卤化物钙钛矿的光致发光（PL）是一项巨大的挑战，而了解激子动力学背后的机制可以提供一个有价值的解决方案。在此，我们通过铝掺杂调节自陷激子（STE），在环境条件下实现了CsAgInCl中宽带发射的增强。低温测量表明，由于缺陷态的存在，STE发射具有不均匀性，并且会受到热猝灭的影响。铝掺杂后，黄-里斯因子（-因子）增加，导致更好的电子-声子耦合和高密度的STE态。飞秒瞬态吸收（fs-TA）结果提供了对激子分布动力学的见解，激子分布动力学通过从自由激子（FE）到STE的梯度能级发生，其中每个STE态可能拥有更高的量子化能态。总体而言，本研究旨在理解CsAgInCl:Al中STE的自陷和衰减的起源，并强调成分工程在减轻该材料自陷方面的潜力。
