Browsing by Author "Tu, Zong-Yi"

Now showing 1 - 11 of 11

Effective optimization and analysis of white LED properties by using nano-honeycomb patterned phosphor film
(2016-08-22)
Lin, Huang-Yu
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Wang, Sheng-Wen
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Lin, Chien-Chung
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Tu, Zong-Yi
;
Lee, Po-Tsung
This study presents an approach for patterning a polydimethylsiloxane (PDMS) phosphor film with a photonic crystal nano-honeycomb structure on a blue chip package. A phosphor film with a nano-honeycomb structure was patterned and transferred using a nanosphere and used for fabricating remote white light-emitting diodes (w-LEDs). The angular correlated color temperature deviation of the remote phosphor LED could be improved by varying nano-honeycomb structure pitches (450, 750, and 1150 nm). In particular, w-LED samples with excellent color uniformity (Delta CCT ranging from 940 to 440 K) were fabricated from 750-nm w-LED samples with nano-honeycomb-patterned tops. (C) 2016 Optical Society of America
Efficient hybrid white light-emitting diodes by organic-inorganic materials at different CCT from 3000K to 9000K
(2015-04-06)
Chen, Kuo-Ju
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Lai, Yi-Chun
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Lin, Bin-Cheng
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Lin, Chien-Chung
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Chiu, Sheng-Huan
The hybrid white light-emitting didoes (LED) with polyfluoren (PFO) polymer and quantum dot (QD) was investigated using dispensing method at the different correlated color temperature (CCT) for cool and warm color temperature. This result indicates that the hybrid white LED device has the higher luminous efficiency than the convention one, which could be attributed to the increased utilization rate of the UV light. Furthermore, the CIE 1931 coordinate of high quality white hybrid LED with different CCT range from 3000K to 9000K is demonstrated. Consequently, the angular-dependent CCT and the thermal issue of the hybrid white LED device were also analyzed in this study. (C) 2015 Optical Society of America
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
;
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.
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.
Excellent Color Quality of White-Light-Emitting Diodes by Embedding Quantum Dots in Polymers Material
(2016-01-01)
Lin, Huang-Yu
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Wang, Sheng-Wen
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Lin, Chien-Chung
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Chen, Kuo-Ju
;
Han, Hau-Vei
This study employs the polyfluorene composite (called Green B) with several colors of quantum dots to generate the high-color-rendering index (CRI) white LEDs. The Green B polymer is a good candidate to manufacture the hybrid w-LED because of its good quantum efficacy. The hybrid w-LEDs are fabricated by the mixing of Green B with yellow quantum dots and red quantum dots or orange quantum dots to obtain the correlated color temperatures of 3500 and 5500 K. The use of the hybrid polymer/QDs w-LEDs is proved to be beneficial as QD w-LEDs can improve the CRI up to 90 in 3500 K. The luminous efficiency of such devices can be as high as 17.2l m/W.
Highly Efficient Hybrid Quantum Dot Light Emitting Diodes with Prolonged Lifetime
(2015)
Hsu, Shun-Chieh
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Chen, Yin-Han
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Tu, Zong-Yi
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Han, Hau-Vei
;
Lin, Shih-Li
A highly efficient LED is demonstrated by incorporating the colloidal quantum dots and sodium chloride. Further lifetest shows great stability up to 104 hours under 194 mW/cm(2) of UV pump power.
Highly Stable and Efficient Hybrid Quantum Dot Light-Emitting Diodes
(2015-10-01)
Hsu, Shun-Chieh
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Chen, Yin-Han
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Tu, Zong-Yi
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Han, Hau-Vei
;
Lin, Shih-Li
A highly efficient and reliable hybrid quantum dot (QD) light-emitting diode (LED) is demonstrated and analyzed. The CdTe colloidal QDs are embedded in the sodium chloride (NaCI) ionic crystal to prevent external wear. The GaN-based ultraviolet (UV) LED is used as the excitation source. The mixture of colloidal QD/NaCI composite and polymer can be filled inside the standard LED package and optically pumped by the UV LED. Two different filling layer designs are fabricated simultaneously for comparative study. Due to extra scattering brought by the sodium chloride grains, the resultant photon conversion efficiency (POE) can be as high as 72.6% at the medium current level. For the long-term stability assessment, two different UV pumping intensities were set up: One is equivalent to 111 mW/cm(2), and the other is 906 mW/cm(2). With this encapsulation, the stability of the colloidal QD light output over time can be improved, and a prolonged lifetime of 6488 h can be demonstrated under the continuous UV aging condition.
Large area lighting applications with organic dye embedded flexible film
(2015-01-01)
Lin, Huang-Yu
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Tu, Zong-Yi
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Ku, Pei-Cheng
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Lin, Chien-Chung
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Kuo, Hao-Chung
A flexible large area lighting devices have been demonstrated by PDMS films. The (polydimethylsiloxane) PDMS films doped with organic/inorganic materials. The PDMS film is favorable due to its heat stability, good transparency, and flexibility. This study aimed to combine both organic and inorganic materials for flexible large area lighting applications. The architecture consists of blue LEDs coupled to a leaky waveguide that is covered with the PDMS film. The white light was generated with the poly (9, 9-dioctylfluorene-co-benzothiadiazole) F8BT blended into the PDMS slurry. Organic wavelength conversion materials were chosen owing to their ability to decompose in nature. The more conventional inorganic phosphors such as YAG are difficult to decompose and may present environmental issues which can bring concerns in many lighting applications. These flexible PDMS films had thicknesses of 100 mu m, 440 mu m, and 980 mu m. The resulting white light devices had color temperatures of 8944K, 4863K, and 4429K, respectively. In this study, we have also compared the performance of the organic versus conventional YAG phosphor embedded films.
Large-area, uniform white light LED source on a flexible substrate
(2015-09-21)
Sher, Chin-Wei
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Chen, Kuo-Ju
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Lin, Chien-Chung
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Han, Hau-Vei
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Lin, Huang-Yu
This study demonstrates the flexible white LED structure with high lumen efficiency and uniform optical performance for neutral white and warm white CCT. Flip-chip LEDs were attached on a polyimide substrate with copper strips as electrical and thermal conduction paths. Yellow phosphors are mixed with polydimenthysiloxane (PDMS) to provide mechanical support and flexibility. The light efficiency of this device can reach 120 lm/W and 85% of light output uniformity of the emission area can be achieved. Moreover, the optical simulation is employed to evaluate various designs of this flexible film in order to obtain uniform output. Both the pitch between the individual devices and the thickness of the phosphor film are calculated for optimization purpose. This flexible white LED with high lumen efficiency and good reliability is suitable for the large area fixture in the general lighting applications. (C) 2015 Optical Society of America
Luminous efficiency enhancement of white light-emitting diodes by using a hybrid phosphor structure
(2015-02-19)
Lin, Bing-Cheng
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Huang, Jhih-Kai
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Chen, Kuo-Ju
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Chiu, Sheng-Huan
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Tu, Zong-Yi
This paper presents a "hybrid" structure for the coating of yellow YAG: Ce3(+) phosphor on blue GaN-based light-emitting diodes (LEDs). The luminous efficiency of the hybrid phosphor structure improved by 5.9% and 11.7%, compared with the conventional remote and conformal phosphor structures, respectively, because of the increased intensity of the yellow component. The hybrid structure also has an advantage in the phosphor usage reduction for the LEDs. Furthermore, the electric intensity of the hybrid phosphor structure was calculated for various thicknesses by conducting TFCalc32 simulation, and the enhanced utilization of blue rays was verified. Finally, the experimental results were consistent with the simulation results performed using the Monte-Carlo method. (C) 2015 Society of Photo-Optical Instrumentation Engineers (SPIE)
Wide-Range Correlated Color Temperature Light Generation From Resonant Cavity Hybrid Quantum Dot Light-Emitting Diodes
(2015-07-01)
Chen, Kuo-Ju
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Lin, Chien-Chung
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Han, Hau-Vei
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Lee, Chia-Yu
;
Chien, Shih-Hsuan
This study presents extremely uniform colloidal quantum dot white light-emitting diodes (QD-WLEDs) that demonstrate a high color rendering index (CRI) and correlated color temperatures (CCTs) ranging from 2500 to 4500 K. Experimental results indicate that the structure of the distributed Bragg reflector (DBR) containing a stopband in the UV region enhances the intensity output of both monochromatic QD-LEDs and QD-WLEDs by reflecting the unconverted UV light back onto the package to excite the QDs further. Furthermore, the angular CCT uniformity of the QD-WLEDs also improved considerably because of the dependence of the DBR structure on the incident angle. The angular CCT deviation in the range of -70 degrees to 70 degrees decreased to 39 K and the CRI of the WLED is higher than 90. The high-CRI and uniform angular CCT QD-WLED containing the DBR demonstrates potential applicability as the lighting source of next-generation display devices and solid-state lighting.