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Browsing by Author "Chen, Nai-Chuan"

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    Optical joint density of states in InGaN/GaN-based multiple-quantum-well light-emitting diodes
    (2011-11-15)
    Wang, Yu-Shou
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    Chen, Nai-Chuan
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    Lu, Chun-Yi
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    Chen, Jenn-Fang
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    電子物理學系
    The optical joint densities of states of three InGaN/GaN-based light-emitting diodes with different emission wavelengths (violet, blue and green) operated at various currents were investigated. The results indicate that the blueshift of the emission with increasing current is related to the variation in optical joint density of states. Thus, the blueshift is ascribed to the screening of the piezoelectric field by carriers. A tail at the low-energy end of the density of states, corresponding to localized states, was found, and the presence of these tails broadens the spectra of the devices. (C) 2011 Elsevier B.V. All rights reserved.
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    Significant color space blue-shift of green OLED emitter with sustaining lifetime and substantial efficiency enhancement
    (2017-08-28)
    Li, Jung-Yu
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    Chen, Shih-Pu
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    Siao, Huei-Jhen
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    Wu, Jin-Han
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    Chen, Guan-Yu
    In this study, we demonstrate that by embedding a plasmonic coupling metal layer beneath the active layer of an organic light-emitting diode, the resultant device is capable of inducing significant blue shifts in CIE color space coordinates of emitting light from the green emitting material without compromising the lifetime of the parent material. The implemented device consists of multilayers of organic emitting materials sandwiched by two thin metal layers to form a metal-dielectric-metal (MDM) cavity-like structure. The original green emission with CIE coordinates of (0.22, 0.56) was significantly color space blue-shifted to CIE coordinates of (0.10, 0.53). The MDM device exhibits an efficiency of 62 cd/A at a luminance of 1000 cd/m(2), which represents a two-fold enhancement of current efficiency. Moreover, the spectral peak intensity is 4.3 times higher than that in a conventional device, which is much higher than that expected for an optical microcavity model, suggesting that the Purcell effect resulting from the coupling of surface plasmon waves may contribute to the extra enhancement of emission intensity. Published by AIP Publishing.
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