Browsing by Author "Shu, G. W."

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Distance dependence of energy transfer from InGaN quantum wells to graphene oxide
(2013-08-01)
Lin, T. N.
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Huang, L. T.
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Shu, G. W.
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Yuan, C. T.
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Shen, J. L.
We report the distance-dependent energy transfer from an InGaN quantum well to graphene oxide (GO) by time-resolved photoluminescence (PL). A pronounced shortening of the PL decay time in the InGaN quantum well was observed when interacting with GO. The nature of the energy-transfer process has been analyzed, and we find the energy-transfer efficiency depends on the 1/d(2) separation distance, which is dominated by the layer-to-layer dipole coupling. (C) 2013 Optical Society of America
Efficient energy transfer from InGaN quantum wells to Ag nanoparticles
(2013)
Shu, G. W.
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Chiu, C. H.
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Huang, L. T.
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Lin, T. N.
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Yang, C. C.
Nonradiative energy transfer from an InGaN quantum well to Ag nanoparticles is unambiguously demonstrated by the time-resolved photoluminescence. The distance dependence of the energy transfer rate is found to be proportional to 1/d(3), in good agreement with the prediction of the dipole interaction calculated from the Joule losses in acceptors. The maximum energy-transfer efficiency of this energy transfer system can be as high as 83%.
Energy transfer from InGaN quantum wells to Au nanoclusters via optical waveguiding
(2011-03-14)
Shu, G. W.
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Lin, C. C.
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Lin, H. T.
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Lin, T. N.
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Shen, J. L.
We present the first observation of resonance energy transfer from InGaN quantum wells to Au nanoclusters via optical waveguiding. Steady-state and time-resolved photoluminescence measurements provide conclusive evidence of resonance energy transfer and obtain an optimum transfer efficiency of similar to 72%. A set of rate equations is successfully used to model the kinetics of resonance energy transfer. (C) 2011 Optical Society of America
Improving Performance of InGaN/GaN Light-Emitting Diodes and GaAs Solar Cells Using Luminescent Gold Nanoclusters
(2009)
Yang, M. D.
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Wu, S. W.
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Shu, G. W.
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Wang, J. S.
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Shen, J. L.
We studied the optoelectronic properties of the InGaN/GaN multiple-quantum-well light emitting diodes (LEDs) and single-junction GaAs solar cells by introducing the luminescent Au nanoclusters. The electroluminescence intensity for InGaN/GaN LEDs increases after incorporation of the luminescent Au nanoclusters. An increase of 15.4% in energy conversion efficiency is obtained for the GaAs solar cells in which the luminescent Au nanoclusters have been incorporated. We suggest that the increased light coupling due to radiative scattering from nanoclusters is responsible for improving the performance of the LEDs and solar cells. Copyright (C) 2009 M. D. Yang et al.
Influence of pulsed laser annealing on the optical properties of ZnO nanorods
(2012-08-01)
Lin, T. N.
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Huang, C. P.
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Shu, G. W.
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Shen, J. L.
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Hsiao, C. S.
"The effect of pulsed laser annealing (PLA) on the photoluminescence (PL) properties of ZnO nanorods was investigated. As the fluence of pulsed laser increases, the UV PL in ZnO nanorods shows a general increasing trend, except at a range of fluences from 10 to 70?mJ/cm2. It is found that the treatment with the PLA at the fluence of 70?mJ/cm2 leads to a larger improvement of crystalline properties than that with rapid thermal annealing (RTA). The relationship between PL intensity and fluence of pulsed lasers can be well explained by a combination of the deterioration in surface crystallinity and the increased donor densities after PLA."
Interrelation of transport and optical properties in gold nanoclusters
(2010-09-20)
Shu, G. W.
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Chen, T. Y.
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Shen, J. L.
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Lin, C. A. J.
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Chang, W. H.
Temperature dependence of the electrical conductivity and photoluminescence (PL) in Au nanoclusters (NCs) is investigated. The correlation of the conductivity and PL in Au NCs at different temperatures is evident: (i) for T < 50 K, both the conductivity and PL intensity decrease with temperature, which suggests thermal structural fluctuations; (ii) for 50 K < T < 90 K, conductivity and PL are explained by variable range hopping; (iii) for 90 K < T < 170 K, simple thermal activated hopping dominates in conductivity, with a rate-equation model proposed to analyze the carrier transfer in PL. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3491288]
Interrelation of transport and optical properties in gold nanoclusters
(2010-09-20)
Shu, G. W.
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Chen, T. Y.
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Shen, J. L.
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Lin, C. A. J.
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Chang, W. H.
Temperature dependence of the electrical conductivity and photoluminescence (PL) in Au nanoclusters (NCs) is investigated. The correlation of the conductivity and PL in Au NCs at different temperatures is evident: (i) for T < 50 K, both the conductivity and PL intensity decrease with temperature, which suggests thermal structural fluctuations; (ii) for 50 K < T < 90 K, conductivity and PL are explained by variable range hopping; (iii) for 90 K < T < 170 K, simple thermal activated hopping dominates in conductivity, with a rate-equation model proposed to analyze the carrier transfer in PL. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3491288]
Measuring junction temperature of GaAs solar cells using pulse-width modulation photoluminescence
(2010-07-01)
Yang, M. D.
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Liao, W. C.
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Shu, G. W.
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Liu, Y. K.
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Shen, J. L.
A photoluminescence (PL) technique is presented to measure the junction temperature of GaAs solar cells. The technique utilizes the pulse-width modulation of excitation laser and the temperature dependence of PL spectra. The apparent change of PL energy on duty cycle can be advantageously used for the determination of the junction temperature. Varying the duty cycle from 10% to 75% causes an increase of 2.9 Kin the junction temperature of GaAs solar cells. The carrier temperature of the junction layer was studied to confirm the result obtained from the pulse-width modulation PL (C) 2010 Elsevier Ltd. All rights reserved.
Optical coupling from InGaAs subcell to InGaP subcell in InGaP/InGaAs/Ge multi-junction solar cells
(2013-01-14)
Shu, G. W.
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Lin, J. Y.
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Jian, H. T.
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Shen, J. L.
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Wang, S. C.
Spatially-resolved electroluminescence (EL) images in the triple junction InGaP/InGaAs/Ge solar cell have been investigated to demonstrate the subcell coupling effect. Upon irradiating the infrared light with an energy below bandgap of the active layer in the top subcell, but above that in the middle subcell, the EL of the top subcell quenches. By analysis of EL intensity as a function of irradiation level, it is found that the coupled p-n junction structure and the photovoltaic effect are responsible for the observed EL quenching. With optical coupling and photoswitching effects in the multi-junction diode, a concept of infrared image sensors is proposed. (C)2012 Optical Society of America
Photoluminescence studies of InAs/GaAs quantum dots covered by InGaAs layers
(2010-01-15)
Shu, G. W.
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Wang, J. S.
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Shen, J. L.
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Hsiao, R. S.
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Chen, J. F.
Photoluminescence (PL), PL excitation (PLE), and time-resolved PL were used to study effects of InGaAs layers on the optical properties of InAs/GaAs quantum dots (QDs). A rich fine structure in the excited states of confined excitons (up to n = 4 quantum states) was observed, providing useful information to study the quantum states in the InAs/GaAs QDs. A significant redshift of the PL peak energy for the QDs covered by InGaAs layers was observed, attributing to the decrease of the QD strain and the lowing of the quantum confinement. (C) 2009 Elsevier B.V. All rights reserved.
The photoluminescence decay time of self-assembled InAs quantum dots covered by InGaAs layers
(2006-12-14)
Shu, G. W.
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Wang, C. K.
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Wang, J. S.
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Shen, J. L.
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Hsiao, R. S.
The temperature dependence of the time-resolved photoluminescence (PL) of self-assembled InAs quantum dots (QDs) with InGaAs covering layers was investigated. The PL decay time increases with temperature from 50 to 170 K, and then decreases as the temperature increases further above 170 K. A model based on the phonon-assisted transition between the QD ground state and the continuum state is used to explain the temperature dependence of the PL decay time. This result suggests that the continuum states are important in the carrier capture in self-assembled InAs QDs.
Waveguide based energy transfer with gold nanoclusters for detection of hydrogen peroxide
(2014)
Lin, T. N.
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Chang, Y. L.
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Shu, G. W.
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Yuan, C. T.
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Shen, J. L.
H2O2 detection that uses fluorescence resonance energy transfer from InGaN quantum wells to Au nanoclusters via optical waveguiding has been developed. Steady and time-resolved photoluminescence studies have been used to demonstrate the waveguide-based energy transfer. H2O2 detection is achieved by the quenching of the red emission from Au nanoclusters. Advantages of the sensing technique include the capability of visual detection and large area analysis.