Herein, a highly-efficient quantum dot light-emitting diode (QLED) with stacked blue and yellow quantum dot (QD) layers can be demonstrated to output white light. A buffer layer of ZnO nanoparticles (NPs) inserted between two QD layers can prevent them from mixing and penetrating. In order to promote charge balance, Zn0.95Mg0.05O was employed as the electron transport layer (ETL), which can block excessive electrons due to the 0.07 eV higher conduction band minimum (CBM) level compared to that of pristine ZnO, leading to the suppression of exciton quenching. In addition, the lower defect concentration and lowered conductivity of Zn0.95Mg0.05O due to the reduction of oxygen vacancies by doping the Mg element into ZnO can also benefit the inhibition of exciton quenching. The device can be demonstrated with a maximum luminance current efficiency of 24.6 cd A-1 and power efficiency of 25.8 lmW-1, exhibiting a 19% and 38% enhancement, respectively. The strategy demonstrated here demonstrates a promising way to realize highly efficient white QLEDs and also other optoelectronic devices.
https://pubs.rsc.org/en/content/articlehtml/2018/tc/c8tc03014f