Abstract
Effective and bright light-emitting-diodes (LEDs) have attracted broad interests in fundamental research and industrial application, especially on short wavelength LEDs. In this paper, a well aligned ZnO nanorod arrays grown on the p-GaN substrate to form a heterostructured light-emitting diode and Al nanoparticles (NPs) were decorated to improve the electroluminescence performance. More than 30-folds enhancement of the electroluminescence intensity was obtained compared with the device without Al NPs decoration. The investigation on the stable and transient photoluminescence spectraof the ZnO nanorod arrays before and after Al NPs decoration demonstrated that the metal surface plasmon resonance coupling with excitons of ZnO leads to the enhancement of the internal quantum efficiency (IQE). Our results provide aneffective approach to design novel optoelectronic devices such as light-emitting diodes and plasmonic nanolasers.
Highlights
Surface plasmon (SP), as collective charge oscillationat metal/dielectric interface, has been actively employed to improve the luminous efficiency of light-emitting materials and devices[18,19,20,21,22]
Heterojunction LEDs decorated with Ag NPs, and the improvement was attributed to the resonant coupling between excitons of ZnO and localized surface plasmon (SP) in Ag NPs
Many researches demonstratedthat the SP coupling at metal/semiconductor interface could increase the density of states, accelerate the recombination rate, and enhance the internal quantum efficiency
Summary
The ratio of the emission centered at 400 nm induced by interface recombination to the ultraviolet emission from ZnO nanorods increased with the decoration of Al nanoparticles, which revealed that the efficient coupling occurs between the excitons of ZnO and the SPs of Al. Figure 2b shows that the absorption of Al NPs mainly exists in UV region, which is more benefit for the recombination of ZnO excitons. TRPL results showedthat the PL decay time of LEDs decorated with Al nanoparticleswas significantly decreased compared to that of the bare LEDs. And the Purcell enhancement factor Fp reaches up to 6.3, which indicated that the spontaneousemission rate was increased by the energyresonant coupling betweenthe excitons of ZnO and the SPs of Alnanoparticles. These findings demonstrate that SP coupling is oneof the most interesting methods for developing efficient LEDs, as themetal can be used as an electrical contact and for excitingplasmons
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