Thickness-Dependence of Exciton-Exciton Annihilation in Halide Perovskite Nanoplatelets

TL;DR

This study investigates how the exciton-exciton annihilation (EEA) process in halide perovskite nanoplatelets depends on their thickness and size, revealing a strong power-law relationship crucial for optoelectronic applications.

Contribution

It provides the first detailed analysis of EEA dependence on nanoplatelet thickness and lateral size, highlighting the importance of precise dimensional control in 2D nanocrystals.

Findings

EEA lifetimes are extremely short, around 7-60 ps.

EEA lifetime scales with thickness as d^5.3.

Larger lateral dimensions lead to increased EEA lifetimes.

Abstract

Exciton-exciton annihilation (EEA) and Auger recombination are detrimental processes occurring in semiconductor optoelectronic devices at high carrier densities. Despite constituting one of the main obstacles for realizing lasing in semiconductor nanocrystals (NCs), the dependencies on NC size are not fully understood, especially for those with both weakly and strongly confined dimensions. Here, we use differential transmission spectroscopy to investigate the dependence of EEA on the physical dimensions of thickness-controlled 2D halide perovskite nanoplatelets (NPls). We find the EEA lifetimes to be extremely short on the order of 7-60 ps. Moreover, they are strongly determined by the NPl thickness with a power-law dependence according to {\tau}_2~d^5.3. Additional measurements show that the EEA lifetimes also increase for NPls with larger lateral dimensions. These results show that a precise control of the physical dimensions is critical for deciphering the fundamental laws governing the process especially in 1D and 2D NCs.