Trion Formation Hampers Single Quantum Dot Performance in Silane-Coated FAPbBr3 Quantum Dots

TL;DR

This study compares silane-coated and PEAC8C12-passivated FAPbBr3 quantum dots, revealing that silane coating improves photostability at room temperature but hampers performance at 4K due to increased trion formation and non-radiative processes.

Contribution

The paper introduces a comparative analysis of silane-coated versus zwitterionic ligand passivated FAPbBr3 quantum dots, highlighting temperature-dependent effects on their single-photon emission properties.

Findings

Silane-coated quantum dots show comparable room-temperature performance to PEAC8C12 passivation.

At 4K, silane-coated dots exhibit faster photobleaching and blue-shifting.

Silane coating leads to increased trion populations at low temperatures.

Abstract

We explore silane-coated formamidinium lead bromide (FAPbBr3) quantum dots as single photon emitters and compare them to FAPbBr3 quantum dots passivated with a phosphoethylammonium derivative (PEAC8C12), which represents current state-of-the-art in zwitterionic molecular surface ligand passivation. We compare properties including single-photon purity (g2(t)), linewidth, blinking, and photostability. We find that at room temperature, these silane-coated dots perform comparably to the PEAC8C12 passivation in terms of single-photon performance metrics, while exhibiting improvements in photostability. However, we find that at 4K, silane-coated FAPbBr3 quantum dots perform worse than the PEAC8C12-passivated samples, exhibiting faster blue-shifting and photobleaching under illumination. Analysis of fluorescence lifetime intensity distributions from the photon-counting data indicates increased efficiency of fast non-radiative processes in the silane-coated quantum dots at 4K. We propose a trion related degradation pathway at low temperatures that is consistent with the observed kinetics and estimate that at 4K with 6.1 uJ/cm2, 472 nm excitation the silane-coated quantum dots build up double the trion population of their PEAC8C12-passivated counterparts.