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

Zn-Doped SnO₂ NPs as Electron Transport Layer in Green CdSe/ZnS Quantum Dot Light-Emitting Diodes

SnO2 nanoparticles (NPs) have been used as an electron transport layer (ETL) in quantum dot light-emitting diodes (QLEDs) to achieve stable and high-performance devices. However, SnO2 NPs with high electron mobility cause the problem of imbalanced charge injection and transport in QLEDs. Meanwhile, the SnO2 NPs synthesized at low temperature have hydroxyl (−OH) groups, which could damage the performance of QLEDs. Here, Zn doping was applied to modulate the properties of SnO2 NPs and achieve better carrier balance in green CdSe/ZnS QLED. The maximum current efficiency (CE) of QLED with 5 wt % Zn-doped SnO2 NPs is 2.3-fold higher than that of SnO2-based QLED. In addition, a small-molecule 4,4′-bis­(carbazole-9-yl)-1,1′-biphenyl (CBP)-mixed poly­(9-vinylcarbazole) (PVK) layer was used as a hole transport layer to facilitate the hole injection and charge balance. As a result, a maximum external quantum efficiency (EQE) of 5.03% is obtained for the best performance device. The T50 lifetime at a luminance of 100 cd/m2, for a device based on 5 wt % Zn-doped SnO2 ETL, is 9141 h, which is 2.29-fold longer than the reference one. This work provides a new strategy to obtain high-performance and stable display arrays

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