Abbas Abdullah S, Chabeda Daniel, Weinberg Daniel, Limmer David T, Rabani Eran, Paul Alivisatos A
Department of Materials Science and Engineering, University of Berkeley, Berkeley, CA, USA.
Department of Chemistry, The University of Chicago, Chicago, IL, USA.
Nat Commun. 2025 Jul 11;16(1):6401. doi: 10.1038/s41467-025-60848-5.
Lead halide perovskite nanocrystals have attracted intense interest due to their desirable optical properties, diverse structural features, and size-tunable excitonic structure. Here we show that, under ambient conditions, a non-monotonic trend in radiative lifetime emerges from the interplay of size, lattice symmetry and excitonic structure. Small nanocrystals exhibit long radiative lifetimes due to weakly emissive excitons, but the oscillator strength increases and shortens the lifetime for nanocrystals approaching intermediate confinement. For larger nanocrystals with higher exciton density of states (DOS), the radiative lifetime is lengthened due to depopulation of the bright exciton manifold into thermally accessible dim states. A size-dependent structural symmetry lowering transition from cubic to orthorhombic is observed by XRD and MD simulations, and the non-monotonic radiative lifetime trend emerges only in lower symmetry structures with an increased dim exciton DOS. These findings shed light on the impact of nanocrystal size and structure on radiative lifetime and pave the way for tailored optical materials in various optical applications.
卤化铅钙钛矿纳米晶体因其理想的光学性质、多样的结构特征和尺寸可调的激子结构而备受关注。在此我们表明，在环境条件下，辐射寿命呈现出非单调趋势，这源于尺寸、晶格对称性和激子结构之间的相互作用。小尺寸纳米晶体由于激子发光较弱而具有较长的辐射寿命，但对于接近中间限制的纳米晶体，振子强度增加并缩短了寿命。对于具有较高激子态密度（DOS）的较大纳米晶体，由于明亮激子流形向热可及暗态的跃迁，辐射寿命延长。通过X射线衍射（XRD）和分子动力学（MD）模拟观察到从立方到正交的尺寸依赖性结构对称性降低转变，并且非单调辐射寿命趋势仅出现在具有增加的暗激子DOS的较低对称性结构中。这些发现揭示了纳米晶体尺寸和结构对辐射寿命的影响，并为各种光学应用中定制光学材料铺平了道路。
