Unraveling photoexcitation dynamics at “dots-in-a-perovskite” heterojunctions from first-principles
Abstract
Both organohalide perovskites and colloidal quantum dots are attractive and promising materials for optoelectronic applications. Recent experiments have combined the two to create “quantum dot-in-perovskite” assemblies for highly efficient light emissions. In this work, we unravel photoexcitation dynamics at the interface between the perovskite and the quantum dot by means of first-principles non-adiabatic molecular dynamics simulations. We find that such assemblies adopt the type-I band structure and are free of defect states. The interfacial and the electronic structure are robust against the thermal fluctuations at 300 K. The lowest excitation is predicted to be localized entirely on the quantum dot and the photoexcited charge transfer takes place in a picosecond timescale. The charge transfer dynamics of the photoexcited electron and hole exhibits a moderate asymmetry, which can be attributed to the differences in electronic coupling between the donor and the acceptor. The ultrafast and balanced charge transfer dynamics endows the ‘dot-in-a-crystal’ devices with unprecedented performance, which could lead to important applications in photovoltaics, photocatalysis, and infrared light emissions.