Effect of SiO₂ Spacer-Layer Thickness on Localized Surface Plasmon-Enhanced ZnO Nanorod Array LEDs

Abstract

Localized surface plasmon (LSP)-enhanced ultraviolet LEDs have been constructed via spin-coating Ag nanoparticles onto ZnO/SiO2 core/shell nanorod array/p-GaN heterostructures. Different from the previous reports where the dielectric spacer-layer thickness was determined only through photoluminescence (PL) characterization, the SiO2 shell thickness in this work is also optimized by actual electroluminescence (EL) measurements to maximize the enhancement. It is interesting to find that the enhancement ratios derived from PL and EL measurements demonstrate different thickness dependences on SiO2 shell: an optimal 3.5-fold PL enhancement was obtained at the SiO2 thickness of 16 nm, while an "abnormal" 7-fold EL enhancement was achieved at the thickness of 12 nm. Time-resolved spectroscopy studies, as well as theoretical estimations and numerical simulations, reveal that the higher-ratio EL enhancement stems from joint contributions, both internal-quantum-efficiency improvement induced by exciton-LSP coupling and light-extraction-efficiency improvement aroused by photon-LSP coupling.

Enhanced Electroluminescence from ZnO Quantum Dot Light‐Emitting Diodes via Introducing Al2O3 Retarding Layer and Ag@ZnO Hybrid Nanodots

“…As shown in Figure a, the Ag@ZnO sample shows a faster spontaneous emission rate than the pure ZnO QDs. Considering that both free and localized excitons may contribute to the ZnO UV emission, the two PL decay curves should be fitted by a biexponential attenuation model . By a weighted average of two time constants of fast and slow components, the effective fluorescence lifetimes for the Ag@ZnO hybrid nanodots and pure ZnO QDs (τ* and τ) are calculated as 630 and 860 ps, respectively.…”

One-Dimensional Zinc Oxide Nanomaterials for Application in High-Performance Advanced Optoelectronic Devices

“…Therefore, the MgZnO-coated device exhibited higher stability than that of the uncoated one because surface adsorption on the nanorods was suppressed by the MgZnO coating. SiO 2 [96] and MgO [97] can also be used as passivation materials to improve the performance of 1D ZnO nanostructure LEDs. Another effective approach to improve the luminous efficiency of LEDs is to introduce LSPs into the LED structure.…”

“…After decoration with Ag nanoparticles, the UV emission intensity of the ZnO/MgZnO core/shell nanorod array showed ã 9-fold enhancement compared with that of the device without Ag nanoparticles because of coupling with LSPs. The next year, the same group constructed LSP-enhanced UV LEDs by spin-coating Ag nanoparticles on ZnO/SiO 2 core/shell nanorod array/p-GaN heterostructures; a schematic diagram of this LED structure is illustrated in Figure 14a [96]. The EL intensity was enhanced when both Ag nanoparticles and a SiO 2 spacer layer were coated on the surface of the ZnO nanorods, as shown in Figure 14b.…”

Improved Optical Property and Lasing of ZnO Nanowires by Ar Plasma Treatment

“…When dimension decreases, the quantum confinement effect yields a substantial density of states near the band edges and enhanced radiative recombination due to carrier confinement is achieved. However, for one-dimensional nanostructure like nanowires, due to the large surface to volume ratio, the optical property of the materials is seriously degraded by surface trap states (SS) and surface adsorbed species [5,6]. Therefore, it is necessary to modify the surface of the low-dimensional materials for improved optical performance.…”