Emissive Surface Traps Lead to Asymmetric Photoluminescence Line Shape in Spheroidal CsPbBr3 Quantum Dots

TL;DR

This study investigates how emissive surface traps in spheroidal CsPbBr3 quantum dots cause asymmetric photoluminescence line shapes, revealing surface trap effects and their passivation to improve emission symmetry.

Contribution

It uncovers the role of surface traps in photoluminescence asymmetry and demonstrates passivation methods to mitigate this effect in spheroidal CsPbBr3 quantum dots.

Findings

Red photoluminescence tail caused by surface traps

Surface traps located on (111) surfaces

Passivation with phenethyl ammonium bromide restores symmetry

Abstract

The morphology of quantum dots plays an important role in governing their photophysics. Here, we explore the photoluminescence of spheroidal CsPbBr3 quantum dots synthesized via the room-temperature trioctlyphosphine oxide/PbBr2 method. Despite photoluminescence quantum yields nearing 100%, these spheroidal quantum dots exhibit an elongated red photoluminescence tail not observed in typical cubic quantum dots synthesized via hot injection. We explore this elongated red tail through structural and optical characterization including small-angle x-ray scattering, transmission electron microscopy and time-resolved, steady-state, and single quantum dot photoluminescence. From these measurements we conclude that the red tail originates from emissive surface traps. We hypothesize that these emissive surface traps are located on the (111) surfaces and show that the traps can be passivated by adding phenethyl ammonium bromide, resulting in a more symmetric line shape