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CdSe/CdTe II型胶态量子阱中长寿命的单激子、带电激子和双激子
王俊慧,梁桂杰,吴凯丰*
作者单位E-mail
王俊慧 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  
梁桂杰 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  
吴凯丰* 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 kwu@dicp.ac.cn 
摘要:
关键词:  
DOI:10.1063/1674-0068/30/cjcp1711206
分类号:
基金项目:This work was supported by the start-up funding from Dalian Institute of Chemical Physics, Chinese Academy of Sciences, and the Collaborative Innovation Center of Chemistry for Energy Materials (iChEM-2011).
Long-lived Single Excitons, Trions, and Biexcitons in CdSe/CdTe Type-Ⅱ Colloidal Quantum Wells
Jun-hui Wang,Gui-jie Liang,Kai-feng Wu*
Abstract:
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 typeⅡ 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.
Key words:  Solar energy  Excited state lifetime  Exciton  Trion  Biexciton  Type-II quantum wells  Nanoplatelets  Auger recombination