Long-lived Single Excitons, Trions, and Biexcitons in CdSe/CdTe Type-II Colloidal Quantum Wells  

CdSe／CdTeII型胶态量子阱中长寿命的单激子、带电激子和双激子

作　　者：王俊慧 梁桂杰 吴凯丰 

机构地区：[1]中国科学院大连化学物理研究所分子反应动力学国家重点实验室能源材料化学协同创新中心,大连116023

出　　处：《Chinese Journal of Chemical Physics》2017年第6期649-656,I0001,共9页化学物理学报（英文）

摘　　要：Light-harvesters with long-lived excited states are desired for efficient solar energy conversion systems. Many solar-to-fuel conversion reactions, such as H2 evolution and CO2 reduction, require multiple sequential electron transfer processes, which leads to a complicated situation that excited states involves not only excitons （electron-hole pairs） but also multi-excitons and charged excitons. While long-lived excitons can be obtained in various systems （e.g., semiconductor nanocrystals）, multi-excitons and charged excitons are typically shorted-lived due to nonradiative Auger recombination pathways whereby the recombination energy of an exciton is quickly transferred to the third carrier on a few to hundreds of picoseconds timescale. In this work, we report a study of excitons, trions （an exciton plus an additional charge）, and biexcitons in CdSe/CdTe colloidal quantum wells or nanoplatelets. The type- II band alignment effectively separates electrons and holes in space, leading to a single exciton lifetime of 340 ns which is -2 order of magnitudes longer than that in plane CdSe nanoplatelets. More importantly, the electron-hole separation also dramatically slows down Auger decay, giving rise to a trion lifetime of 70 ns and a biexciton lifetime of 11 ns, among the longest values ever reported for colloidal nanocrystals. The long-lived exciton, trion, and biexciton states, combined with the intrinsically strong light-absorption capability of two-dimensional systems, enable the CdSe/CdTe type-II nanoplatelets as promising light harvesters for efficient solar-to-fuel conversion reactions.

关 键 词：Solar energy Excited state lifetime Exciton TRION BIEXCITON Type-II quan-tum wells NANOPLATELETS Auger recombination 

分 类 号：O[理学]