Visible light-emitting Ce-doped ZnO nanorods [NRs] without a post thermal annealing process were grown by hydrothermal method on a Si (100) substrate at a low temperature of 90°C. The structural investigations of Ce-doped ZnO NRs showed that the Ce3+ ions were successfully incorporated into the ZnO lattice sites without forming unwanted Ce-related compounds or precipitates. The optical investigation by photoluminescence spectra shows that the doped Ce3+ ions in the ZnO NRs act as an efficient luminescence center at 540 nm which corresponds to the optical transition of 5d → 4f orbitals in the Ce3+ ions. The photoluminescence intensity of the Ce-doped ZnO NRs increased with the increasing content of the Ce-doping agent because the energy transfer of the excited electrons in ZnO to the Ce3+ ions would be enhanced by increased Ce3+ ions.
We report a controllable way of changing the emission patterns of GaN-based blue light-emitting diodes (LEDs) using ZnO nanorods (NRs) grown hydrothermally. The shape of the ZnO NRs was controlled using seed layers for flower, askance, and vertical structures. The electrical properties of the LEDs with the ZnO NRs did not degrade, while the integrated electroluminescence intensity increased compared with that of the bare LEDs. The emission patterns of the LEDs were broadened as the inclination angle of the ZnO NRs increased. These are attributed to the ZnO NRs acting a role in scattering and guiding the light wave efficiently.
In this study, we have fabricated and characterized the silicon [Si] wire solar cells with conformal ZnO nanorod antireflection coating [ARC] grown on a Al-doped ZnO [AZO] seed layer. Vertically aligned Si wire arrays were fabricated by electrochemical etching and, the p-n junction was prepared by spin-on dopant diffusion method. Hydrothermal growth of the ZnO nanorods was followed by AZO film deposition on high aspect ratio Si microwire arrays by atomic layer deposition [ALD]. The introduction of an ALD-deposited AZO film on Si wire arrays not only helps to create the ZnO nanorod arrays, but also has a strong impact on the reduction of surface recombination. The reflectance spectra show that ZnO nanorods were used as an efficient ARC to enhance light absorption by multiple scattering. Also, from the current-voltage results, we found that the combination of the AZO film and ZnO nanorods on Si wire solar cells leads to an increased power conversion efficiency by more than 27% compared to the cells without it.
Surface plasmon (SP)-enhanced light emission mechanism has been investigated for the Ag-coated ZnO/Al2O3 core/shell nanorods (NRs). Structural characterizations showed that the ZnO NRs were covered by conformal Al2O3 layer and coated by Ag nanoparticles (NPs). The optical studies by photoluminescence (PL) showed abnormal variation of PL intensity with increasing the thickness of Al2O3. For the Ag NPs-coated ZnO NRs without Al2O3 shell layer, the PL emission quenched due to direct transfer of the photo-excited electrical carriers from ZnO NRs to Ag NPs. With thin Al2O3 layers less than 15 nm, the PL intensity increased with increasing the thickness of Al2O3 layers due to weakening of the Förster-type energy transfer while strong SP-mediated PL emission enhancement. For thicker Al2O3 layers than 15 nm, however, the PL intensity decreased with increasing the thickness of Al2O3 layers due to weakening of SP-mediated PL emission enhancement.
Light-emitting CdSe quantum dot (QD) -ZnO nanorod (NR) hybrid structures were fabricated via wet chemical methods. Structural investigations indicated that the nano-sized CdSe QDs were formed on the ZnO NRs. Optical investigations showed that the energy band gap of the CdSe QDs was changed by varying the number of deposition cycles of CdSe due to the quantum confinement effect. The emissions from the hybrid structures depended on the existence of an Al2O3 shell layer on the ZnO NRs, which acted as an electrical barrier layer blocking charge carrier losses from the CdSe QDs to the ZnO NRs.
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