Ethanedithiol treatment on zinc oxide films for highly efficient quantum dot light-emitting diodes by reducing exciton quenching

Surface modification of ZnO nanoparticles with ethanedithiol (EDT) has been studied to minimize exciton loss at the ZnO/quantum dots (QDs) interface and to improve the efficiency of QD light-emitting diodes (QLEDs). The EDT treatment has been demonstrated to fill oxygen vacancies and reduce carboxylate and hydroxyl ligands on the surface of the ZnO nanoparticles from the x-ray photoelectron spectroscopy analysis. The reduction of oxygen vacancies makes the ZnO films more hydrophobic and maintains the optical bandgap under ambient conditions. EDT treatment shifts the energy level up by 0.47 eV by modifying the surface of ZnO. Non-radiative recombination processes at the ZnO/QDs interface such as interfacial charge transfer and energy transfer are reduced through the upshifted energy level and reduced surface defects. The brightness of the QLED with EDT treatment on ZnO was improved by more than 330% having a maximum luminance of 59 , 500 c d / m 2 compared to the QLED with pristine ZnO. The maximum current efficiency of the QLEDs has been improved from 54.3 cd/A to 73.4 cd/A, which is 35% higher than ZnO-based QLEDs.