Kaur Gurpreet, Babu K Justice, Ghosh Hirendra N
Institute of Nano Science and Technology, Mohali, Punjab 160062, India.
Radiation and Photochemistry Division, Bhabha Atomic Research Centre, Mumbai 400085, India.
J Phys Chem Lett. 2020 Aug 6;11(15):6206-6213. doi: 10.1021/acs.jpclett.0c01724. Epub 2020 Jul 21.
Photovoltaic devices with CsPbBr nanocrystals as the working layer are generally subjected to wide variance of extreme temperatures during operation. Thus, the underlying photophysics, which is undeniably a temperature-dependent entity, demands intricate understanding. In this finding, with the assistance of temperature-dependent transient absorption spectroscopy, an endeavor has been made to disentangle the detrimental conflict between polaron formation and hot carrier relaxation for CsPbBr nanocrystal systems. Carrier relaxation pathways are seen to diverge drastically upon varying the lattice temperature from 300 to 5 K. Acquired results indicate the involvement of polarons for retarded carrier cooling dynamics observed at 300 K, whereas its absence at lower temperatures (<200 K) provides the basis for relatively quicker cooling. Additionally, despite the expected participation from the polaron due to the onset of strong carrier-longitudinal optical phonon coupling at 200 K, the reason for its absence in the cooling dynamics at 200 K has been revealed.
以CsPbBr纳米晶体作为工作层的光伏器件在运行过程中通常会经历极端温度的大幅变化。因此，其潜在的光物理过程，这无疑是一个依赖温度的实体，需要深入理解。在本研究中，借助温度相关的瞬态吸收光谱，人们努力厘清CsPbBr纳米晶体系统中极化子形成与热载流子弛豫之间的有害冲突。当晶格温度从300 K变化到5 K时，载流子弛豫途径明显不同。所得结果表明，在300 K观察到的延迟载流子冷却动力学涉及极化子，而在较低温度（<200 K）下不存在极化子则为相对较快的冷却提供了基础。此外，尽管由于在200 K时强载流子 - 纵向光学声子耦合的出现，预期极化子会参与其中，但已揭示了其在200 K冷却动力学中不存在的原因。
