High-performance tricolored white lighting electroluminescent devices integrated with environmentally benign quantum dots.

Abstract

The electroluminescent (EL) performances of quantum dot-light-emitting diodes (QLEDs) based on either high-quality CdSe- or Cd-free quantum dots (QDs) have been greatly improved during the last decade, exclusively aiming at monochromatic devices for display applications. Meanwhile, work on white lighting QLEDs integrated particularly with Cd-free QDs remains highly underdeveloped. In this work, the solution-processed fabrication of tricolored white lighting QLEDs comprising three environmentally benign primary color emitters of II-VI blue and green ZnSeTe and I-III-VI red Zn-Cu-In-S (ZCIS) QDs is explored. The emitting layer (EML) consists of two different QD layers stacked on top of the other with an ultrathin ZnMgO nanoparticle buffer layer inserted in the middle, with both blue and green QDs mixed in one layer, and red QDs placed in a separate layer. The stacking order of the bilayered EML architecture is found to control the exciton recombination zone and thus crucially determine the EL performance of the device. The optimal tricolored white device yields outstanding EL performances such as 5461 cd m-2 luminance, 5.8% external quantum efficiency, and 8.4 lm W-1 power efficiency, along with a near-ideal color rendering index of 95, corresponding to the record quantities reported among Cd-free white lighting QLEDs.