Modified Charge Injection in Green InP Quantum Dot Light-Emitting Diodes Utilizing a Plasma-Enhanced NiO Buffer Layer

With the growing concern for green and environmentally friendly quantum dots (QDs), the investigation of low-toxicity heavy-metal-free light-emitting materials and devices has become a research hotspot. Due to their high quantum yield, tunable emission, and environmentally friendly properties, the low-toxicity III–V InP quantum dot light-emitting devices (QLEDs) have great application potential in next-generation full-color displays and lighting. In this work, charge injection in high-performance green InP QLEDs was modified by using a low-temperature atomic layer-deposited (ALD) nickel oxide (NiO) buffer layer. The device with the NiO buffer layer effectively suppressed the nonradiative recombination process and enhanced the hole injection, exhibiting a 1.35-fold enhanced external quantum efficiency (EQE). Moreover, different oxygen plasma-enhanced conditions were applied to the deposition of the NiO film. As the ambient oxygen flux increased (50–200 sccm), Ni2+ and interstitial oxygen vacancies were generated within the NiO film, which effectively improved the hole injection and promoted the carrier balance injection. The best-performing device with a 100 sccm O2–NiO film realized a 2.36 times higher EQE (6.75%) than the device without the NiO buffer layer, with a maximum current efficiency (CE) of 12.73 cd/A. The experimental results provide an effective strategy to further improve the charge balance and performance of InP-based QLEDs