Strong Collectivity of Optical Transitions in Lead Halide Perovskite Quantum Dots

Perovskite quantum dots (QDs) are attractive semiconducting materials for large-scale and low-cost optoelectronic devices owing to their size-tunable bandgap, high photoluminescence quantum yield, and outstanding charge transport. Comprehending/understanding their fundamental photo-physical properties is of significant applied importance. However, first-principles theoretical studies elucidating their optical features are relatively less explored. In this study, we investigate the optical characteristics of CH3NH3PbX(3) (X = I, Br, Cl) perovskite QDs having sizes below the Bohr exciton radius. We base our calculations on the linear combination of atomic orbitals (LCAO) real-time-propagation rt-TDDFT technique. Our results underline the strong collectivity in the optical excitations, ascertained using the decomposition weight of the electron-hole transition via transition contribution maps. We also demonstrate an appealing route to tune the optical excitations subject to an external electric field. The results presented in this work will contribute to enhancing our understanding of the optical properties of perovskite QDs.