Performance improvement of blue quantum dot light-emitting diodes by facilitating electron transportation and suppressing electroplex emission

Abstract The enhanced device performance of blue quantum dot light-emitting diodes (QD-LEDs) was demonstrated; a positive aging process was used to improve electron transport and suppress electroplex emission, which results from the interface between the QD-emitting layer and the ZnO electron-transporting layer (ETL). This electroplex interface functions as a low-energy recombination center, leading to energy loss and further decreasing the device performance. Without the positive aging process, the QD-LED exhibited poor electrical and electroluminescent (EL) characteristics, as well as an EL spectrum containing a strong electroplex emission with a peak at 635 nm. A positive aging process was applied by dripping a surface active reagent on the cathode before device encapsulation. The active reagent treatment led to suppression of the electroplex emission and enhanced device performance by promoting Al atoms into ZnO ETL to facilitate electron transport at the QD/ZnO interface. Furthermore, static positive aging was investigated by assessing the QD-LEDs at different storage times to observe the maturing process. After 409-hrs of maturing, the QD-LEDs exhibited an optimal device performance with favorable CEmax and EQEmax values of 6.2 cd/A and 8.7%, respectively. At a current density of 1 mA/cm2, the QD-LED exhibited a maximum overall efficiency enhancement factor of 7.1 after the positive aging process. In particular, electroplex suppression was correlated with the enhancement of device performance, caused by an upgraded QD/ZnO interface, formed during the positive aging process, benefits the electron transport.