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 QLED

Plasmon–Microcavity Coupling and Fabry–Pèrot Lasing in a ZnO:Ga Microwire/p-Type Gallium Nitride Heterojunction

In recent years, electroluminescent devices of ZnO have been the focus of attention and research. In this paper, we fabricated a ZnO:Ga microwire/p-type gallium nitride heterojunction light-emitting diode and found a lasing emission near the silver electrode. We interpret this lasing as trap-state FP-mode lasing because a series of small peaks appear in the spectrum and the positions of three lasing peaks are close to the emission peak from the trap state. After sputtering gold on the surface of the ZnO:Ga microwire, the luminescence of the device was enhanced and anomalous spectral signals appeared at a reverse current of 20 mA. The luminescence enhancement is due to the hot electron transfer induced by plasmons, and the strange spectral phenomenon was attributed to the Fano resonance caused by plasmon–microcavity coupling. The above research can provide some guidance for the design of LEDs and laser devices

Blue Quantum Dot Light-Emitting Diodes with High Electroluminescent Efficiency

High-efficiency blue CdSe/ZnS quantum dots (QDs) have been synthesized for display application with emission peak over 460 nm with the purpose of reducing the harmful effect of short-wavelength light to human eyes. To reach a better charge balance, different size ZnO nanoparticles (NPs) were synthesized and electrical properties of ZnO NPs were analyzed. Quantum dot light-emitting diodes (QLEDs) based on as-prepared blue QDs and optimized ZnO NPs have been successfully fabricated. Using small-size ZnO NPs, we have obtained a maximum current efficiency (CE) of 14.1 cd A^–1 and a maximum external quantum efficiency (EQE) of 19.8% for QLEDs with an electroluminescence (EL) peak at 468 nm. To the best of our knowledge, this EQE is the highest value in comparison to the previous reports. The CIE 1931 color coordinates (0.136, 0.078) of this device are quite close to the standard (0.14, 0.08) of National Television System Committee (NTSC) 1953. The color saturation blue QLEDs show great promise for use in next-generation full-color displays