High Quantum Efficiency of Band-Edge Emission from ZnO Nanowires

Abstract

External quantum efficiency (EQE) of photoluminescence as high as 20% from isolated ZnO nanowires were measured at room temperature. The EQE was found to be highly dependent on photoexcitation density, which underscores the importance of uniform optical excitation during the EQE measurement. An integrating sphere coupled to a microscopic imaging system was used in this work, which enabled the EQE measurement on isolated ZnO nanowires. The EQE values obtained here are significantly higher than those reported for ZnO materials in forms of bulk, thin films or powders. Additional insight on the radiative extraction factor of one-dimensional nanostructures was gained by measuring the internal quantum efficiency of individual nanowires. Such quantitative EQE measurements provide a sensitive, noninvasive method to characterize the optical properties of low-dimensional nanostructures and allow tuning of synthesis parameters for optimization of nanoscale materials.

Correlation between structural and electronic order–disorder effects and optical properties in ZnO nanocrystals

“…Therefore characterization depends on the nature and structure of the imperfection and the electronic states of the solid. [59][60][61][62][63]67,68 In particular, all the defects discussed above play a key role in streamlining the physical and chemical properties of semiconductor materials directly associated with the structural and electronic order-disorder effects which can exist in ZnO nanocrystals with different charged states or in a neutral state typically represented by V [60][61][62][63]72,73 which are generated in the rapid crystallization of such materials during the MAH process, and have been reported in this study. In this case, experimental results presented in Fig.…”

“…67,68 In particular, Van Vugt et al 69 have reported a strong exciton-photon coupling in ZnO nanowires at room temperature. The phononassisted recombination determines the temperature-dependence of the PL signal intensity which decreases with an increase in temperature due to phonon-assisted transition effects in the ZnO crystal.…”

“…The results indicate the relationship between the broad PL band and the degree of order-disorder in ZnO nanocrystals and are in agreement with other studies. 22,23,[60][61][62][63]67,68 A few years ago, we proposed a cluster model to explain complex metal oxide PL emissions of perovskite and scheelitebased materials. [73][74][75][76] In this model, the clusters are used as basic units of the materials to explain the structural and electronic order-disorder effects as well as their physical properties.…”

Room-Temperature Laser Emission of ZnO Nanowires Explained by Many-Body Theory

“…This indicates that, at least for the majority of cases, room-temperature lasing in ZnO nanowires does not involve excitons. Parameters affecting the laser threshold are the nanowire dimensions [13,33], the quality of the nanowire, which is strongly dependent on the growth conditions [34], and the substrate supporting the wire [35].…”

The Influence of Parameters of Ink-Jet Printing on Photoluminescence Properties of Nanophotonic Labels Based on Ag Nanoparticles for Smart Packaging

“…It should be noted that the use of Ag nanoparticles in packages has several advantages over semiconductor luminescent nanoparticles and luminescent particles of other metals; namely, Ag nanoparticles can have higher quantum luminescence yields than ZnO [19][20][21], and they are nontoxic in contrast to CdS and CdSe. Colloidal Au nanoparticles are stable while utilized for nanophotonic applications related to light trapping [22], but Ag nanoparticles are significantly cheaper than Au nanoparticles.…”