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Nanoscale Res Lett ; 14(1): 236, 2019 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-31309306


This paper proposes a new encapsulation structure for aluminum nitride-based deep UV light-emitting diodes (DUV-LEDs) and eutectic flip chips containing polydimethylsiloxane (PDMS) fluid doped with SiO2 nanoparticles (NPs) with a UV-transparent quartz hemispherical glass cover. Experimental results reveal that the proposed encapsulation structure has considerably higher light output power than the traditional one. The light extraction efficiency was increased by 66.49% when the forward current of the DUV-LED was 200 mA. Doping the PDMS fluid with SiO2 NPs resulted in higher light output power than that of undoped fluid. The maximum efficiency was achieved at a doping concentration of 0.2 wt%. The optical output power at 200 mA forward current of the encapsulation structure with NP doping of the fluid was 15% higher than that without NP doping. The optical output power of the proposed encapsulation structure was 81.49% higher than that of the traditional encapsulation structure. The enhanced light output power was due to light scattering caused by the SiO2 NPs and the increased average refractive index. The encapsulation temperature can be reduced by 4 °C at a driving current of 200 mA by using the proposed encapsulation structure.

Nanoscale Res Lett ; 14(1): 182, 2019 May 29.
Artigo em Inglês | MEDLINE | ID: mdl-31144059


This study proposes a novel direct-lit mini-chip-scale packaged light-emitting diode (mini-CSPLED) backlight unit (BLU) that used quantum dot (QD) film, diffusion plate, and two prism films to improve brightness uniformity. Three different luminous intensity units, 120° mini-CSPLED, 150° mini-CSPLED, and 180° mini-CSPLED with different emission angle structures were fabricated using a CSP process. In terms of component characteristics, although the 180° mini-CSPLED light output power is about loss 4% (at 10 mA) compared with 150° mini-CSPLED, it has a large emission angle that forms a planar light source that contributes to improving the BLU brightness uniformity and reduced quantity of LEDs at the same area. In terms of BLU analysis, the blue mini-CSPLEDs with different emission angles excite the different QD film thicknesses; the chromaticity coordinates conversion to the white light region. The BLU brightness increases as the QD film thickness increases from 60, 90, and 150 µm. This result can achieve a brightness uniformity of 86% in a 180° mini-CSPLED BLU + 150-µm-thick QD films as compared to the 120° mini-CSPLED BLU and 150° mini-CSPLED BLU.

Opt Express ; 24(2): A341-9, 2016 Jan 25.
Artigo em Inglês | MEDLINE | ID: mdl-26832586


A novel combination of blue LED chips, transparent glass substrates and phosphors with PDMS thin film is demonstrated. The flip-chip bonding technology is applied to facilitate this design. The ZrO(2) nanoparticles are also doped into the PDMS film to increase light scattering. The resultant luminous efficiency shows an 11% enhancement when compared to the regular COG device. The variation of correlated color temperature of such devices is also reduced to 132K. In addition to these changes, the surface temperature is reduced from 121°C to 104°C due to good thermal dissipation brought by ZrO(2) nanoparticles.

Appl Opt ; 54(28): E23-9, 2015 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-26479658


Light guides have been widely used for transforming line sources into planar illuminators for lighting and display applications. Solid light guides provide good uniformity but still have the issues of heavy weight and material absorption, especially for large applications. Hollow light guides solve the problem of weight, but the uniformity is relatively poor or efficiency could be sacrificed for enhancing uniformity. In this paper, a hollow light guide with edge-lit LED sources has been proposed to simultaneously resolve the issues of weight, uniformity, and efficiency. The major approach is to modulate the LED luminous intensity profile by a ring of parabolic surface with continuously varied focal length. The modulated light emitting profile directly makes up sufficient uniformity on the planar surface, and extra components are not required. The prototype is a circular planar illuminator with a diameter of 178 mm and a weight of 240 g. The experiment shows an overall efficiency of 82.37%, with a uniformity of 83.7%. The weight of the whole module is 40% lighter than that of a solid light guide with the same size.

Appl Opt ; 54(28): E94-101, 2015 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-26479672


The penetration of LED light bulbs into the lighting market is growing quickly in recent years due to significant increase of LED efficiency and reduction of cost. One major issue to be improved is the overall light bulb efficiency, which can fulfill "Energy Star for Lamps" while keeping sufficiently high efficiency. The efficiency issue results mainly from the high directionality of the LED sources and the corresponding solutions to make the emission more diverse. In this paper, a diffusion white reflection sheet (DWRS) with an array of holes is proposed as a high efficiency solution for modulating a light emission profile with SMD type LED source. The hole size is adjusted with fixed hole pitch to both maximize the efficiency and meet the omnidirectional specification. In addition, the concept of thermal plastic insertion molding metal is proposed for thermal management without fins for cooling. The prototype demonstrates the efficiency (Ef.) of 87.6% and LED pad temperature of 85°C, which shows the feasibility as a total solution for high efficiency LED omnidirectional bulbs.