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Browsing by Author "Wu, Jin-Han"

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    Dimmable sunlight-like organic light emitting diodes with ultra-high color rendering index
    (2016-05)
    Wu, Jin-Han
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    Chi, Chien-An
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    Chiang, Chang-Lin
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    Chen, Guan-Yu
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    Lin, Yi-Ping
    We propose novel dimmable sunlight-like white organic light-emitting diodes that were fabricated using three luminophores to form an emitting spectrum similar to black body radiation at 2250 K with ultra-high color rendering index (CRI) value of 91, which nearly remained the constant at various luminance values ranging from 100 to more than 2500 cd/m(2) at Commission Internationale de l\'Eclairage chromaticity coordinates of (0.51, 0.41). Introducing charge modification layers suppressed the energy transfer between the emitting material layers and increased the probability of carrier recombination. Moreover, we reveal that covering long-wavelength ranges played a vital role in achieving high CRI values; the CRI values of a spectrum artificially shifted toward a long-wavelength direction (from 610 to 620 nm) remained constant, whereas those of a spectrum shifted toward a short-wavelength direction (from 610 to 600 nm) dropped to 79. (C) 2016 Elsevier B.V. All rights reserved.
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    Enabling Lambertian-Like Warm White Organic Light-Emitting Diodes with a Yellow Phosphor Embedded Flexible Film
    (2014-01-01)
    Chen, Cheng-Chang
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    Lin, Huang-Yu
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    Li, Cheng-Hung
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    Wu, Jin-Han
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    Tu, Zong-Yi
    We demonstrate in this report a new constructive method of fabricating white organic light-emitting devices (OLEDs) with a flexible plastic film embedded with yellow phosphor. The flexible film is composed of polydimethylsiloxane (PDMS) and fabricated by using spin coating followed by peeling technology. From the results, the resultant electroluminescent spectrum shows the white OLED to have chromatic coordinates of 0.38 and 0.54 and correlated color temperature of 4200 K. The warm white OLED exhibits the yield of 10.3 cd/A and the luminous power efficiency of 5.4 lm/W at a luminance of 1000 cd/m(2). A desirable Lambertian-like far-field pattern is detected from the white OLEDs with the yellow phosphor containing PDMS film. This method is simple, reproducible, and cost-effective, proving to be a highly feasible approach to realize white OLED.
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    Enabling Lambertian-Like Warm White Organic Light-Emitting Diodes with a Yellow Phosphor Embedded Flexible Film
    (2014-01-01)
    Chen, Cheng-Chang
    ;
    Lin, Huang-Yu
    ;
    Li, Cheng-Hung
    ;
    Wu, Jin-Han
    ;
    Tu, Zong-Yi
    We demonstrate in this report a new constructive method of fabricating white organic light-emitting devices (OLEDs) with a flexible plastic film embedded with yellow phosphor. The flexible film is composed of polydimethylsiloxane (PDMS) and fabricated by using spin coating followed by peeling technology. From the results, the resultant electroluminescent spectrum shows the white OLED to have chromatic coordinates of 0.38 and 0.54 and correlated color temperature of 4200 K. The warm white OLED exhibits the yield of 10.3 cd/A and the luminous power efficiency of 5.4 lm/W at a luminance of 1000 cd/m(2). A desirable Lambertian-like far-field pattern is detected from the white OLEDs with the yellow phosphor containing PDMS film. This method is simple, reproducible, and cost-effective, proving to be a highly feasible approach to realize white OLED.
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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
    ;
    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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