Li Qiuyang, He Sheng, Lian Tianquan
Department of Chemistry, Emory University, 1515 Dickey Drive, NE, Atlanta, Georgia 30322, United States.
Nano Lett. 2020 Aug 12;20(8):6162-6169. doi: 10.1021/acs.nanolett.0c02461. Epub 2020 Jul 28.
Cadmium chalcogenide nanoplatelets (NPLs) possess unique properties and have shown great potential in lasing, light-emitting diodes, and photocatalytic applications. However, the exact natures of the band-edge exciton and single carrier (electron and hole) states remain unclear, even though they affect the key properties and applications of these materials. Herein, we study the contribution of a single carrier (electron or hole) state to phase space filling of single exciton states of cadmium chalcogenide NPLs. With pump fluence dependent TA study and selective electron removal, we determine that a single electron and hole states contribute 85% and 12%, respectively, to the blocking of the excitonic transition in CdSe/ZnS core/shell NPLs. These observations can be rationalized by a model of band-edge exciton and single carrier states of 2D NPLs that differs significantly from that of quantum dots.
硫族化镉纳米片（NPLs）具有独特的性质，并且在激光、发光二极管和光催化应用中展现出了巨大潜力。然而，尽管带边激子和单载流子（电子和空穴）态会影响这些材料的关键性质和应用，但其确切性质仍不明确。在此，我们研究了单载流子（电子或空穴）态对硫族化镉纳米片单激子态相空间填充的贡献。通过依赖泵浦通量的瞬态吸收（TA）研究和选择性电子去除，我们确定在CdSe/ZnS核壳纳米片中，单电子态和单空穴态分别对激子跃迁的阻挡贡献了85%和12%。这些观察结果可以通过二维纳米片的带边激子和单载流子态模型得到合理解释，该模型与量子点的模型有显著差异。
