Department of Physics, Indian Institute of Technology Roorkee, Roorkee, Haridwar, Uttarakhand247667, India.
National Physical Laboratory, Dr. K.S. Krishnan Road, New Delhi110012, India.
J Phys Chem Lett. 2023 Jan 26;14(3):730-736. doi: 10.1021/acs.jpclett.2c03541. Epub 2023 Jan 17.
Lead-free CsAgBiBr double perovskites have recently emerged as a possible alternative to lead-based halide perovskites for photovoltaic and optoelectronic applications. Significant research efforts have been devoted toward device engineering to enhance the performance of CsAgBiBr double-perovskite-based photovoltaic and optoelectronic devices; however, less attention has been paid to address their intrinsic photophysical properties. In this work, we have shown that the small polaron formation under photoexcitation and polaron localization limits the carrier dynamics in CsAgBiBr double halide perovskites. Furthermore, temperature-dependent ac conductivity measurement reveals that single polaron hopping is the dominant conduction mechanism. Ultrafast transient absorption spectroscopy reveals that a deformed lattice under photoexcitation leads to the formation of small polarons which act as self-trapped states (STSs) and lead to the ultrafast trapping of charge carriers. Our findings provide an in-depth understanding of intrinsic limitations of CsAgBiBr perovskites, which can be applicable for other bismuth-based semiconductors.
无铅 CsAgBiBr 双钙钛矿作为一种可能的替代物，正在取代含铅卤化物钙钛矿，应用于光伏和光电领域。在器件工程方面，已经开展了大量的研究工作，以提高基于 CsAgBiBr 双钙钛矿的光伏和光电器件的性能；然而，对于解决其固有光物理性质的问题，关注较少。在这项工作中，我们表明，光激发下小极化子的形成和极化子局域限制了 CsAgBiBr 双卤化物钙钛矿中的载流子动力学。此外，温度依赖的交流电导测量表明，单极化子跳跃是主要的导电机理。超快瞬态吸收光谱表明，光激发下晶格的变形导致小极化子的形成，小极化子作为自陷态（STSs），导致电荷载流子的超快俘获。我们的发现深入了解了 CsAgBiBr 钙钛矿的固有局限性，这对于其他基于铋的半导体也具有适用性。
