Light-Induced Activation of Forbidden Exciton Transition in Strongly Confined Perovskite Quantum Dots
Light-Induced Activation of Forbidden Exciton Transition in Strongly Confined Perovskite Quantum Dots
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DOI：
10.1021/acsnano.8b06649
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发表时间：
2018-12-01
期刊：
影响因子：
17.1
通讯作者：
Son, Dong Hee
中科院分区：
文献类型：
--
作者：
Rossi, Daniel;Wang, Hua;Son, Dong Hee
我们报道了在CsPbBr3钙钛矿量子点中，由对称性破缺极化子介导的禁戒激子跃迁的强光诱导激活，该极化子改变了受限激子跃迁的光学选择定则。激活的禁戒跃迁导致在带隙上方的瞬态吸收光谱中出现强烈的泵浦诱导吸收，而原始的宇称禁戒跃迁就位于此处。与许多其他半导体量子点不同，CsPbBr3量子点中激子的光激发通过晶格畸变极化子产生足够大的扰动，从而开启了形式上的禁戒跃迁。与体相或弱受限的CsPbBr3相比，由于极化子对受限空间中激子跃迁的更强影响，强受限量子点中禁戒跃迁的激活更为显著。这种非线性光学性质凸显了CsPbBr3量子点中光激发载流子与晶格的紧密耦合，使得能够通过光实现禁戒激子跃迁。
We report the strong light-induced activation of forbidden exciton transition in CsPbBr3 perovskite quantum dots mediated by the symmetry-breaking polaron that modifies the optical selection rule of the confined exciton transition. The activated forbidden transition results in an intense pump-induced absorption in the transient absorption spectra above the bandgap, where the original parity-forbidden transition was located. In contrast to many other semiconductor quantum dots, photo-excitation of an exciton in CsPbBr3 quantum dots creates a sufficiently large perturbation via a lattice-distorting polaron, which turns on the formally forbidden transition. Compared to the bulk or weakly confined CsPbBr3, the activation of the forbidden transition in strongly confined quantum dots is much more prominent due to the stronger influence of the polaron on exciton transitions in the confined space. This nonlinear optical property highlights the intimate coupling of the photoexcited charge carriers with the lattice in the CsPbBr3 quantum dots, allowing access to the forbidden exciton transitions with light.