Highly Efficient and Bright Inverted Top-Emitting InP Quantum Dot Light-Emitting Diodes Introducing a Hole-Suppressing Interlayer

InP quantum dots (QDs) based light-emitting diodes (QLEDs) are considered as one of the most promising candidates as a substitute for the environmentally toxic Cd-based QLEDs for future displays. However, the device architecture of InP QLEDs is almost the same as the Cd-based QLEDs even though the properties of Cd-based and InP-based QDs are quite different in their energy levels and shapes. Thus, it is highly required to develop a proper device structure for InP-based QLEDs to improve the efficiency and stability. In this work, efficient, bright, and stable InP/ZnSeS QLEDs based on an inverted top emission QLED (ITQLED) structure by newly introducing a “hole-suppressing interlayer” are demonstrated. The green-emitting ITQLEDs with the hole-suppressing interlayer exhibit a maximum current efficiency of 15.1–21.6 cd A⁻¹ and the maximum luminance of 17 400–38 800 cd m⁻², which outperform the recently reported InP-based QLEDs. The operational lifetime is also increased when the hole-suppressing interlayer is adopted. These superb QLED performances originate not only from the enhanced light-outcoupling by the top emission structure but also from the improved electron–hole balance by introducing a hole-suppressing interlayer which can control the hole injection into QDs.