Shukla Ayushi, Kaur Gurpreet, Babu K Justice, Ghorai Nandan, Goswami Tanmay, Kaur Arshdeep, 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):6344-6352. doi: 10.1021/acs.jpclett.0c01853. Epub 2020 Jul 23.
The performance of the high-end optoelectronic devices is essentially influenced by the intrinsic relaxation mechanisms pursued by the hot carriers. Therefore, the key toward achieving progression in such fields lies in developing a complete understanding of the involved carrier cooling dynamics. In this work, an endeavor has been made to highlight the difference in the cooling mechanisms in 2D CsPbBr nanosheets (NSs) and their 3D counterpart nanocrystals (NCs) with the aid of femtosecond broad-band pump-probe spectroscopy, varying the excitation energies. The exciton and biexciton dynamics in both systems are found to be retarded upon increasing the excitation energy. However, in contrast to 3D NCs, carrier cooling is found to be faster in the 2D system, regardless of the excitation energy used, attributing this to less efficient charge screening by Fröhlich interaction in low-dielectric medium. A similar trend is replicated in the biexciton formation rate since the formation is also found to be faster in NSs compared to NCs.
高端光电器件的性能本质上受热载流子所遵循的固有弛豫机制影响。因此，在这些领域取得进展的关键在于全面理解所涉及的载流子冷却动力学。在这项工作中，借助飞秒宽带泵浦 - 探测光谱，通过改变激发能量，努力突出二维CsPbBr纳米片（NSs）及其三维对应物纳米晶体（NCs）冷却机制的差异。发现随着激发能量的增加，两个系统中的激子和双激子动力学均受到延迟。然而，与三维纳米晶体相比，二维系统中的载流子冷却更快，无论所使用的激发能量如何，这归因于低介电介质中弗罗利希相互作用的电荷屏蔽效率较低。双激子形成速率也呈现类似趋势，因为与纳米晶体相比，纳米片中的形成也更快。
