Ultra-bright and energy-efficient quantum-dot LEDs by idealizing charge injection

TL;DR

This paper presents a simple reductive treatment to improve charge injection in quantum-dot LEDs, resulting in ultra-bright, energy-efficient devices suitable for lighting, displays, and laser applications, surpassing existing benchmarks.

Contribution

The study identifies and addresses oxidative species in the electron-injection layer, achieving a significant boost in brightness and efficiency in QLEDs through a novel reductive treatment.

Findings

Achieved at least 2.6-fold higher brightness than existing QLEDs.

Demonstrated QLEDs with brightness suitable for laser diodes at moderate bias.

Created white-light QD-blend LEDs surpassing US DOE 2035 targets.

Abstract

Lighting and display, relying on electric and optical down-conversion emission with sluggish power efficiency, account for >15% global electricity consumption1,2. In 2014, quantum-dot (QD) LEDs (QLEDs) with near-optimal external quantum efficiency emerged3 and promised a pathway to avoid the vast down-conversion energy loss4,5. Despite a decade of progress4-22, fabrication of energy-efficient QLEDs with application-relevant brightness remains elusive. Here, the main roadblock is identified as the oxidative species adsorbed in the nanocrystalline electron-injection layer of QLEDs, which is then addressed by a simple reductive treatment to simultaneously boosts electron conductivity and hole blockage of the electron-injection layer. The resulting sub-bandgap-driven QLEDs with optimal efficiency achieve ultra-high brightness across the entire visible spectrum at least 2.6-fold higher than existing benchmarks. The brightness fully satisfies the demands of various forms of lighting and display, which surges to a remarkable level sufficient for QD laser diodes with a moderate bias (~9 V). Optimized electron injection further enables new types of QD-blend LEDs for diffuse white-light sources surpassing the 2035 R&D targets set by the U.S. Department of Energy. Our findings open a door for understanding and optimizing carrier transport in nanocrystalline semiconductors shared by various types of solution-processed optoelectronic devices.