Fabrication of Microlens Arrays with Controlled Curvature by Micromolding Water Condensing Based Porous Films for Deep Ultraviolet LEDs

Peng, Yang; Guo, Xing; Liang, Renli; Mou, Yun; Cheng, Hao; Liu, Sheng

doi:10.1021/acsphotonics.7b00692

Cited by 46 publications

(24 citation statements)

References 43 publications

(60 reference statements)

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“…The red phosphor coated YAG:Ce 3+ PiG achieves different luminescence properties by controlling the number of spin-coating layer. The red phosphor layer with micro-concave patterns was fabricated by the UV assisted and initiative cooling based water condensing, as detailed in our previous work [33]. In order to achieve the micro-concave with various sizes, the viscoelastic state of red phosphor layer was adjusted by UV pre-exposure under 385 nm UV-LED with a power density of 1.5 W/cm 2 for different time of 20 s, 30 s, and 40 s, respectively.…”

Section: Introductionmentioning

confidence: 99%

Flexible fabrication of a patterned red phosphor layer on a YAG:Ce³⁺ phosphor-in-glass for high-power WLEDs

Peng

Mou

Guo

et al. 2018

Opt. Mater. Express

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We proposed a flexible and mask-less approach to directly fabricate a patterned red phosphor layer on a Y 3 Al 5 O 12 :Ce 3+ (YAG:Ce 3+) phosphor-in-glass (PiG) for high-power white light-emitting diodes (WLEDs). This approach was realized by ultraviolet (UV) assisted and initiative cooling based water condensing. A low-temperature precursor glass matrix with a high refractive index was synthesized for the YAG:Ce 3+ PiG. By controlling the UV pre-curing time, the micro-concaves with adjustable sizes were fabricated on the red phosphor layer embedded with UV-curable polymer. With the pre-curing time of 20 s, 30 s, and 40 s, the average aspect ratio of the micro-concave is 1.03, 0.76, and 0.41, respectively. Consequently, the patterned sample achieves a highest luminous efficacy (LE) of 108.5 lm/W at the current of 350 mA, which is 16.2% higher than the unpatterned sample. The corresponding correlated color temperature (CCT) and color rendering index (CRI) are 4831 K and 80.5, respectively. The results demonstrate that the YAG:Ce 3+ PiG coated with the water condensing patterned red phosphor layer is a feasible and effective method to enhance the light extraction and color quality of high-power WLEDs.

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Section: Introductionmentioning

confidence: 99%

Flexible fabrication of a patterned red phosphor layer on a YAG:Ce³⁺ phosphor-in-glass for high-power WLEDs

Peng

Mou

Guo

et al. 2018

Opt. Mater. Express

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“…Fang et al used the UV laser writing method coupled with soft imprint technology to fabricate paraboloidal MLA with varying ARs, which can be easily tuned by changing the exposure laser power [41]. A breath figure method based on water fog condensing was proposed by Peng et al to fabricate the MLA by adjusting the condensing temperature and time [42]. Yang et al proposed to fabrication hexagonal compound eye MLA using a maskless lithography technique based on digital micromirror device which allowed a proper control of the morphology.…”

Section: Introductionmentioning

confidence: 99%

Microlens arrays with adjustable aspect ratio fabricated by electrowetting and their application to correlated color temperature tunable light-emitting diodes

et al. 2019

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We develop a facile, fast, and cost-effective method based on the electrowetting effect to fabricate concave microlens arrays (MLA) with a tunable height-to-radius ratio, namely aspect ratio (AR). The electric parameters including voltage and frequency are demonstrated to play an important role in the MLA forming process. With the optimized frequency of 5 Hz, the AR of MLA are tuned from 0.057 to 0.693 for an increasing voltage from 0 V to 180 V. The optical properties of the MLA, including their transmittance and light diffusion capability, are investigated by spectroscopic measurements and ray-tracing simulations. We show that the overall transmittance can be maintained above around 90% over the whole visible range, and that an AR exceeding 0.366 is required to sufficiently broaden the transmitted light angular distribution. These properties enable to apply the developed MLA films to correlated-color-temperature (CCT)-tunable light-emitting-diodes (LEDs) to enhance their angular color uniformity (ACU). Our results show that the ACU of CCT-tunable LEDs is significantly improved while preserving almost the same lumen output, and that the MLA with the highest AR exhibits the best ACU performance.

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“…Various methods have been adopted for the high‐FF fabrication of MLA. Hexagonal arrays with 100% FF have been demonstrated by self‐assembly methods based on dewetting, localized water condensation, or surface wrinkling, but these approaches typically lack control in the design and positioning of the microlenses. In contrast, photolithography techniques have become the gold standard for the production of customized high‐FF MLA .…”

Section: Introductionmentioning

confidence: 99%

Single‐Shot Laser Additive Manufacturing of High Fill‐Factor Microlens Arrays

Surdo

Carzino

Diaspro

et al. 2018

Advanced Optical Materials

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Various methods have been adopted for the high-FF fabrication of MLA. Hexagonal arrays with 100% FF have been demonstrated by self-assembly methods based on dewetting, [7] localized water condensation, [8] or surface wrinkling, [9] but these approaches typically lack control in the design and positioning of the microlenses. In contrast, photolithography techniques have become the gold standard for the production of customized high-FF MLA. [10][11][12][13] Even if unrivaled industrial upscaling is possible, photolithography is optimized for planar substrates and requires multistep processing in expensive clean room facilities. More importantly, the need of masks imposes an additional limit in the degree of tunability of the MLA designs in timely fashion.Alternatively, direct-write technologies (DWTs) such as inkjet printing, [14] microdispensing, [15] two-photon polymerization, [16] laser-induced forward transfer (LIFT), [17,18] or multibeam interferencebased holography [19] enable the direct and maskless fabrication of polymeric microlenses and MLA with perfectly optical quality on a variety of substrates. In this case, though, the use of liquid prepolymers can result in merging of adjacent microlenses that seriously constraints the attainable FF of the arrays. [20] Recent works to improve the FF using DWTs include the fabrication of concave MLA using laser ablation followed by a replica molding step. [21,22] Despite excellent results in terms of uniformity and FF, this approach impedes the direct fabrication of MLA on substrates of interest. Furthermore, most DWTs require complex systems or ultrafast lasers for parallelization, which limit the overall throughput of these systems. Simply put, a low-cost and maskless technique capable of directly generating high-FF arrays at high-throughputs, with controlled geometry and at targeted positions on nonplanar substrates does not exist.In this work, we present a novel laser-based method for the realization of high-FF polymeric microlens arrays that addresses the limitations of traditional direct-write and photolithographic approaches. Our method, termed laser catapulting or LCP, exploits short (in the nanosecond scale) high-energy laser pulses to transfer polymeric solid microdiscs from a uniform film into targeted positions on a receiver substrate. After thermal reflow, namely the heating of the microdiscs above their glass transition temperature (T g ), planoconvex microlenses are obtained. Notably, the direct printing of discs in the solid-state enables the generation of highly close-packed High fill-factor microlens arrays (MLA) are key for improving photon collection efficiency in light-sensitive devices. Although several techniques are now capable of producing high-quality MLA, they can be limited in fill-factor, precision, the range of suitable substrates, or the possibility to generate arbitrary arrays. Here, a novel additive direct-write method for rapid and customized fabrication of high fill-factor MLA over a variety of substrates is demonstrated. This appro...

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Fabrication of Microlens Arrays with Controlled Curvature by Micromolding Water Condensing Based Porous Films for Deep Ultraviolet LEDs

Cited by 46 publications

References 43 publications

Flexible fabrication of a patterned red phosphor layer on a YAG:Ce³⁺ phosphor-in-glass for high-power WLEDs

Flexible fabrication of a patterned red phosphor layer on a YAG:Ce³⁺ phosphor-in-glass for high-power WLEDs

Microlens arrays with adjustable aspect ratio fabricated by electrowetting and their application to correlated color temperature tunable light-emitting diodes

Single‐Shot Laser Additive Manufacturing of High Fill‐Factor Microlens Arrays

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Fabrication of Microlens Arrays with Controlled Curvature by Micromolding Water Condensing Based Porous Films for Deep Ultraviolet LEDs

Cited by 46 publications

References 43 publications

Flexible fabrication of a patterned red phosphor layer on a YAG:Ce3+ phosphor-in-glass for high-power WLEDs

Flexible fabrication of a patterned red phosphor layer on a YAG:Ce3+ phosphor-in-glass for high-power WLEDs

Microlens arrays with adjustable aspect ratio fabricated by electrowetting and their application to correlated color temperature tunable light-emitting diodes

Single‐Shot Laser Additive Manufacturing of High Fill‐Factor Microlens Arrays

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Flexible fabrication of a patterned red phosphor layer on a YAG:Ce³⁺ phosphor-in-glass for high-power WLEDs

Flexible fabrication of a patterned red phosphor layer on a YAG:Ce³⁺ phosphor-in-glass for high-power WLEDs