Laser patterning of Y3Al5O12:Ce3+ ceramic phosphor platelets for enhanced forward light extraction and angular color uniformity of white LEDs.

We present a facile fabrication process to directly fabricate cone-shaped microwells arrays on single crystal Y3Al5O12:Ce3+ (YAG:Ce) ceramic phosphor platelets (CPPs) by short-pulse laser direct patterning. Compared to unpatterned YAG:Ce CPP with smooth surface, the forward-to-total ratio of emission photons of patterned YAG:Ce CPPs was enhanced from 53.2% up to 78.2%, and the total emission within 4-π degree is 6% higher. The fabricated patterns are also beneficial in increasing the color conversion efficiency of YAG:Ce CPPs by 7.6%. The patterned YAG:Ce CPPs display much better correlated color temperature (CCT) uniformity under varied currents. The angular correlated color temperature uniformity (ACU) of patterned YAG:Ce CPPs reaches as high as 0.933 compared to 0.730 of the unpatterned one. These results suggest that laser patterning of YAG:Ce CPP could effectively manipulate its luminance, chromaticity and illumination pattern, which may lead to further technological advancements for diversified applications of film-type CPPs in highly efficient white LEDs.

[1]  J. Piprek.  Efficiency droop in nitride‐based light‐emitting diodes , 2010 .

[2]  N. Narendran,et al.  Extracting phosphor‐scattered photons to improve white LED efficiency , 2005 .

[3]  Nanopatterning using a simple bi-layer lift-off process for the fabrication of a photonic crystal nanostructure. , 2013, Nanotechnology.

[4]  R. F. Karlicek,et al.  Surface patterning of nonscattering phosphors for light extraction. , 2013, Optics letters.

[5]  Brent C. Stuart,et al.  Optical ablation by high-power short-pulse lasers , 1996 .

[6]  Y. Do,et al.  Analysis of the factors governing the enhanced photoluminescence brightness of Li-doped Y2O3:Eu thin-film phosphors , 2006 .

[7]  Christian Sommer,et al.  A detailed study on the requirements for angular homogeneity of phosphor converted high power white LED light sources , 2009 .

[8]  R. Singh,et al.  Critical issues in enhancing brightness in thin film phosphors for flat-panel display applications , 2002 .

[9]  Klaus Sokolowski-Tinten,et al.  The physical mechanisms of short-pulse laser ablation , 2000 .

[10]  Ji Hye Oh,et al.  Toward scatter-free phosphors in white phosphor-converted light-emitting diodes , 2012, Optics express.

[11]  Shuji Nakamura,et al.  High‐power InGaN single‐quantum‐well‐structure blue and violet light‐emitting diodes , 1995 .

[12]  J. Oh,et al.  Full Extraction of 2D Photonic Crystal Assisted $ \hbox{Y}_{3}\hbox{Al}_{5}\hbox{O}_{12}$:Ce Ceramic Plate Phosphor for Highly Efficient White LEDs , 2014, IEEE Photonics Journal.

[13]  Yuval Golan,et al.  Effect of hot acid etching on the mechanical strength of ground YAG laser elements , 2008 .

[14]  Young Jin Kim,et al.  The effects of substrates and deposition parameters on the growing and luminescent properties of Y3Al5O12:Ce thin films , 2006 .

[15]  粕谷 亮.  Characteristic optical properties of transparent color conversion film prepared from YAG:Ce3+ nanoparticles , 2007 .

[16]  Boris N. Chichkov,et al.  Short-pulse laser ablation of solid targets , 1996 .

[17]  Jinho Ahn,et al.  Various nanofabrication approaches towards two-dimensional photonic crystals for ceramic plate phosphor-capped white light-emitting diodes , 2014 .

[18]  Y. Do,et al.  Fabrication of wafer-scale TiO2 nanobowl arrays via a scooping transfer of polystyrene nanospheres and atomic layer deposition for their application in photonic crystals , 2013 .

[19]  Chun Che Lin,et al.  Advances in Phosphors for Light-emitting Diodes. , 2011, The journal of physical chemistry letters.

[20]  Akio Ikesue,et al.  Fabrication of Polycrystal line, Transparent YAG Ceramics by a Solid‐State Reaction Method , 1995 .

[21]  G. Corman.  Creep of yttrium aluminium garnet single crystals , 1993 .

[22]  Jeong Rok Oh,et al.  2D SiNx photonic crystal coated Y3Al5O12:Ce3+ ceramic plate phosphor for high-power white light-emitting diodes. , 2011, Optics express.

[23]  S. C. Jones,et al.  Recent Progress On Laser-Induced Modifications And Intrinsic Bulk Damage Of Wide-Gap Optical Materials , 1989 .

[24]  Han-Ben Niu,et al.  Effects of YAG: Ce Phosphor Particle Size on Luminous Flux and Angular Color Uniformity of Phosphor-Converted White LEDs , 2012, Journal of Display Technology.

[25]  Jong Kyu Kim,et al.  Solid-State Light Sources Getting Smart , 2005, Science.

[26]  Akio Ikesue,et al.  Fabrication of Polycrystalline, Transparent YAG Ceramics by a Solid- State Reaction Method. , 1996 .

[27]  Setsuhisa Tanabe,et al.  YAG glass-ceramic phosphor for white LED (I): background and development , 2005, SPIE Optics + Photonics.

[28]  J. Meijer.  Laser Beam Machining (LBM), State of the Art and new Opportunities , 2004 .

[29]  Y. Fujimoto,et al.  Properties of transparent Ce:YAG ceramic phosphors for white LED , 2011 .

[30]  Paul H. Holloway,et al.  Luminescence of pulsed laser deposited Eu doped yttrium oxide films , 1997 .