Photoinduced Single- and Multiple-Electron Dynamics Processes Enhanced by Quantum Confinement in Lead Halide Perovskite Quantum Dots

Abstract

Methylammonium lead iodide perovskite (MAPbI) is a promising material for photovoltaic devices. A modification of MAPbI into confined nanostructures is expected to further increase efficiency of solar energy conversion. Photoexcited dynamic processes in a MAPbI quantum dot (QD) have been modeled by many-body perturbation theory and nonadiabatic dynamics. A photoexcitation is followed by either exciton cooling (EC), its radiative (RR) or nonradiative recombination (NRR), or multiexciton generation (MEG) processes. Computed times of these processes fall in the order of MEG < EC < RR < NRR, where MEG is on the order of a few femtoseconds, EC is in the picosecond range, while RR and NRR are on the order of nanoseconds. Computed time scales indicate which electronic transition pathways can contribute to increase in charge collection efficiency. Simulated mechanisms of relaxation and their rates show that quantum confinement promotes MEG in MAPbI QDs.

Low threshold and efficient multiple exciton generation in halide perovskite nanocrystals

“…The small and similar effective masses of the electron and hole are predicted to be favorable for slow hot-carrier cooling and more efficient MEG 36 , 37 . Furthermore, another recent computational work 38 also demonstrated low-threshold MEG (close to 2 E g ) in MAPbI 3 NCs. The authors attributed that the stronger Coulomb coupling between the initial single-exciton and final-biexciton states, and the longer hot-carrier cooling of highly excited states were more conducive for MEG.…”

Recent advances in metal halide perovskite photocatalysts: Properties, synthesis and applications

“…3(b), conventional bulk semiconductor NCs often encounter rapid hot-carrier cooling, so one incident photon usually produces a single pair of electronhole pair. While for some MHP QDs (e.g., MAPbI 3 and FAPbI 3 ) [64,65], when excited by one photon with high energy at least twice of its bandgap, QDs may produce multiple excitons. This phenomenon is well known as the MEG, where the excess energy of absorbed photons can be used for generating excitons.…”

Morphological Engineering of Inorganic Semiconductor VIS-Light-Driven Nanocatalysts: Experimental and Theoretical Understandings

“…This procedure, recently implemented by us for WO3 (see Figure 5-c), 35 although much more cumbersome than the 2D slab approach in the judicious design of the structural models, enables to get a complete picture of the interplay of size and shape of the nanostructures in the opto-electronic properties of the material. In the case of MHPs, both small 59,60 and large 61,62 cluster models (see Figures 5 d-e) have been employed to explore the optoelectronic properties of perovskite materials, but the systematic investigation of the size-shape relationship has never been tackled. Concerning the description of NP/solvent interactions, computationally less demanding implicit models are usually preferred when targeting optical and electronic properties, 63 despite the fact that one needs to consider at least few explicit solvent molecules up to few solvent layers, together with thermal effects, to characterize the catalytic mechanism.…”