Colloidal quantum dots (QDs) of group III-V are considered as promising candidates for next-generation environmentally friendly light emitting devices, yet there appears to be only limited understanding of the underlying electronic and excitonic properties. Using large-scale density functional theory with the hybrid B3LYP functional solving the single-particle states and time-dependent density functional theory accounting for the many-body excitonic effects, we have identified the structural, electronic and excitonic optical properties of InP, GaP and GaInP QDs containing up to a thousand atoms or more. The calculated optical gap of InP QD appears in excellent agreement with available experiments, and it scales nearly linearly with the inverse diameter. The radiative exciton decay lifetime is found to increase surprisingly linearly with increasing the dot size. For GaP QDs, we predict an unusual electronic state crossover at diameter around 1.5 nm whereby the nature of the lowest unoccupied molecular orbital (LUMO) state switches its symmetry from $Γ_{5}$-like at larger diameter to $Γ_{1}$-like at smaller diameter. After the crossover, the absorption intensity of the band-edge exciton states is significantly enhanced. Finally, we find that Vegard's law holds very well for GaInP random alloyed quantum dots down to ultra-small sizes with less than a hundred atoms. The obtained energy gap bowing parameter of this common-cation compound in QD regime appears positive, size-dependent and much smaller than its bulk parentage. The volume deformation, dominating over the charge exchange and structure relaxation effects, is mainly responsible for the QD energy gap bowing. The present work provides a road map for a variety of electronic and optical properties of colloidal QDs in group III-V that can guide spectroscopic studies.
Temperature behavior of the Optical Absorption and Photoluminescence Spectra of InP/ZnS Nanocrystals with a Stabilizing Polyvinylpyrrolidone-based Coating
Optical properties of CsCu$_2$X$_3$ (X=Cl, Br and I): A comparative study between hybrid time-dependent density-functional theory and the Bethe-Salpeter equation
卤化铯铜CsCu $_2$ X $_3$（X=Cl、Br和I）是一类具有有趣且潜在有用的光学性质的全无机钙钛矿，其特征在于独特的激子特征。本文采用含时密度泛函理论（TDDFT）和Bethe-Salpeter方程（BSE），以$GW$准粒子能带结构为输入，计算研究了CsCu $_2$ X $_3$的吸收光谱. TDDFT计算使用几种类型的全球混合交换相关泛函。据发现，由介电常数确定的非局部交换的混合物产生的光谱与BSE非常一致。因此，混合TDDFT出现作为一个有前途的第一性原理方法激子在固体中的影响。
