The influence of Auger recombination on the performance of quantum-dot light-emitting diodes

TL;DR

This paper investigates how Auger recombination impacts the efficiency and performance of quantum-dot LEDs, revealing that controlling this process can significantly improve device performance.

Contribution

It provides a detailed analysis of Auger recombination effects in QD-LEDs and demonstrates that engineered QDs with suppressed Auger decay enhance device efficiency and reduce efficiency roll-off.

Findings

Auger recombination limits QD-LED efficiency.

Charge state of QDs influences recombination processes.

Engineered QDs with alloy layers suppress Auger decay.

Abstract

A growing interest in colloidal quantum dot (QD) based light-emitting diodes (QD-LEDs) has been motivated by the exceptional color purity and spectral tunability of QD emission as well as the amenability of QD materials to highly scalable and inexpensive solution processing. One current challenge in the QD-LED field has been a still incomplete understanding of the role of extrinsic factors (e.g., recombination via QD surface defects) versus intrinsic processes such as multicarrier Auger recombination or electron-hole separation due to applied electric field in defining device efficiency. Here, we address this problem with a study of excited-state dynamics in a series of structurally engineered QDs, which is performed in parallel with characterization of their performance upon incorporation into LEDs. The results of this study indicate that under both zero and forward bias, a significant fraction of the QDs within the active emitting layer is negatively charged and therefore, Auger recombination represents an important factor limiting the efficiency of these devices. We further observe that the onset of the LED efficiency roll-off is also controlled by Auger recombination and can be shifted to higher currents by using newly developed QDs with an intermediate alloy layer at the core-shell interface introduced for suppression of Auger decay. Our findings suggest that further improvement in the performance of QD-LEDs can be achieved by developing effective approaches for controlling Auger recombination and/or minimizing the effects of QD charging via improved balancing of electron and hole injection currents.