Improved device performance of solution-processed red-colored Cu–In–Zn–S-based quantum dot light-emitting diodes enabled by doping TCTA into the emitting layer

Abstract

The working mechanisms in the cadmium-free Cu–In–Zn–S(CIZS)-based quantum dot light-emitting didoes (QD-LEDs) were reported in previous reports, which were mai nly determined by the direct charge injection or the energy transfer. In this paper, we presented an improved device performance in solution-processed red-colored CIZS-based QD-LEDs by doping a small molecule 4,4′,4″-tris-(carbazol-9-yl)- triphenylamine (TCTA) into the emitting layer, and the best peak current efficiency of 3.22 cd A−1 and maximum luminance (Lmax) of 2679 cd m−2 could be achieved by optimizing the doping percentage of TCTA in the CIZS/ZnS nanocrystals (NCs). Such red-colored QD-LEDs exhibited a 210% increase in the current efficiency and no obvious change in the electroluminescence (EL) spectra as compared with the QD-LEDs without TCTA. The improvement of the device performance could be attributed to the synergistic effects of more balanced hole injection and the effective exciton energy transfer from TCTA to the NCs. The balanced hole injection could be verified by the fact that an increased current efficiency in the QD-LEDs by doping TCTA into an organic hole-transport layer.