Ultrastable Quantum-Dot Light-Emitting Diodes by Suppression of Leakage Current and Exciton Quenching Processes

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.