A study of hybrid inverted quantum-dot (QD) light-emitting diodes constructed with and without Al2O3 interlayers is presented. The Al2O3 interlayers are deposited at ZnO/QDs or/and QDs/4,4'-bis(carbazol-9-yl)biphenyl interfaces, resulting in large improvement of device performance, including luminance, current efficiency, and device lifetime. Especially, the devices with QD emitters sandwiched by two Al2O3 layers exhibits outstanding performance, the longest operation lifetime, and mediate efficiency. The maximum current efficiency of 15.3 cd/A is obtained, an enhancement factor of 35% in comparison to that (11.3 cd/A) of conventional device without Al2O3 layer. Moreover, device lifetime is also largely enhanced, over 110 000 h for the device containing two Al2O3 interlayers, nearly 40% enhancement relative to that of conventional device that shows a lifetime of only 80 000 h. On the basis of electrical property and photoluminescence spectroscopy studies, we demonstrate that the Al2O3 interlayers play crucial roles in suppressing the leakage current across the device and reducing exciton quenching induced by ZnO.
Keywords: QLED; exciton quenching; insulating layer; leakage current; quantum dot.