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

Chen, Junchi ORCID iD icon; Fritz, Benjamin ORCID iD icon 1; Liang, Guanwei; Ding, Xinrui; Lemmer, Uli 1,2; Gomard, Guillaume 1,2
1 Lichttechnisches Institut (LTI), Karlsruher Institut für Technologie (KIT)
2 Institut für Mikrostrukturtechnik (IMT), Karlsruher Institut für Technologie (KIT)


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.

Verlagsausgabe §
DOI: 10.5445/IR/1000089937
Veröffentlicht am 22.01.2019
DOI: 10.1364/OE.27.000A25
Zitationen: 27
Zitationen: 22
Cover der Publikation
Zugehörige Institution(en) am KIT Institut für Mikrostrukturtechnik (IMT)
Universität Karlsruhe (TH) – Interfakultative Einrichtungen (Interfakultative Einrichtungen)
Karlsruhe School of Optics & Photonics (KSOP)
Lichttechnisches Institut (LTI)
Publikationstyp Zeitschriftenaufsatz
Publikationsmonat/-jahr 02.2019
Sprache Englisch
Identifikator ISSN: 1094-4087
KITopen-ID: 1000089937
HGF-Programm 43.22.03 (POF III, LK 01) Printed Materials and Systems
Erschienen in Optics express
Verlag Optica Publishing Group (OSA)
Band 27
Heft 4
Seiten A25-A38
Vorab online veröffentlicht am 17.01.2019
Nachgewiesen in Web of Science
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