An efficient green-emitting quantum dot with near-unity quantum yield and suppressed Auger recombination for high-performance light-emitting diodes

Abstract

Near 100% photoluminescence quantum yield (PL QY) is the first target for designing luminescent quantum dots (QDs). Here, an alloyed QD with a core/shell structure of Cd0.194Zn0.806Se0.406S0.594/ZnS is synthesized and characterized by the feature of large core size (about 10 nm) and thin shell (around three ZnS monolayers). It exhibits an efficient green emission with the PL QY of 99.8% and ultra-fast radiative transition rate (kr) of 4.16 × 107 s−1. It demonstrates that the excited state will be rapidly decayed to its ground state through a radiative channel and less vulnerable to non-radiative processes. Under a high pump intensity (254.65 μJ cm−2), the Cd0.194Zn0.806Se0.406S0.594/ZnS QD still owns a long biexciton decay lifetime (τxx) of 1.05 ns and high biexciton QYxx of 25.1%, corresponding to a suppressed non-radiative Auger recombination. The Cd0.194Zn0.806Se0.406S0.594/ZnS QD based light-emitting diode exhibits a peak external quantum efficiency of 20.1% and brightness of over 105 cd m−2 at 5.2 V. We believe that the Cd0.194Zn0.806Se0.406S0.594/ZnS QD not only provides a near-unity QY but also ensures its QD based light-emitting diode (QLED) with an excellent performance, which could be an excellent QD material for QLED applications.