Electrochemically-stable ligands bridge the photoluminescence-electroluminescence gap of quantum dots.

TLDR: Electrochemically-inert ligands are reported as a general material-design strategy for realizing high-performance LEDs based on quantum dots for boosting electroluminescence efficiency and lifetime of the light-emitting-diodes, resulting in record-long operational lifetimes.

Abstract: Colloidal quantum dots are promising emitters for quantum-dot-based light-emitting-diodes. Though quantum dots have been synthesized with efficient, stable, and high colour-purity photoluminescence, inheriting their superior luminescent properties in light-emitting-diodes remains challenging. This is commonly attributed to unbalanced charge injection and/or interfacial exciton quenching in the devices. Here, a general but previously overlooked degradation channel in light-emitting-diodes, i.e., operando electrochemical reactions of surface ligands with injected charge carriers, is identified. We develop a strategy of applying electrochemically-inert ligands to quantum dots with excellent luminescent properties to bridge their photoluminescence-electroluminescence gap. This material-design principle is general for boosting electroluminescence efficiency and lifetime of the light-emitting-diodes, resulting in record-long operational lifetimes for both red-emitting light-emitting-diodes (T95 > 3800 h at 1000 cd m−2) and blue-emitting light-emitting-diodes (T50 > 10,000 h at 100 cd m−2). Our study provides a critical guideline for the quantum dots to be used in optoelectronic and electronic devices. New design principles for bridging the photoluminescence and electroluminescence of colloidal quantum dots are needed. In this work, the authors report electrochemically-inert ligands as a general material-design strategy for realizing high-performance LEDs based on quantum dots.