Study of Polystyrene-Sphere Colloidal Crystal Deposition and Application for Light-Emitting Diodes

• Main Authors: Huang, Kuo-Min, 黃國閔
• Other Authors: Wu, Meng-Chyi
• Format: Others
• Language: en_US
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/02923687180639040582

博士 === 國立清華大學 === 電子工程研究所 === 101 === A suspension of monodisperse colloids has a property of self-assembly into a three-dimensional periodic arrangement structure. This material of colloidal crystal has attracted significant interest on serving as colloidal crystals, which have practical applications in reflectors, resonant cavity, and waveguides. Colloidal crystals and inverted structures have a periodicity in their refractive index. This results in the inhibition of select frequencies of light from propagating within the crystal causing the formation of a gap in the photonic band structure. In this thesis, we describe the deposition and properties of self-assembly colloidal crystals and inverted structures. Self-assembly polystyrene spheres with a diameter about 200 nm were used to fabricate the 3D colloidal-photonic-crystal (CPC) bottom reflector. In addition, the key point is the hydrophilic treatment of substrate and immediately disperses the suspension into the substrate. The equilibrium between the particle transport and crystallization in the aqueous solution helps CPCs to form a face-centered-cubic phase when the solution temperature decreases. This will lead to the improvement of reflectivity at 78% due to the reduced defects (likes dislocations and vacancies) in the CPCs. Finally, the relative light output power and electroluminescence intensity of the light-emitting diodes (LEDs) fabricated with a well-controlled 3D-CPC bottom reflector increases by 155% and 219% as compared to that of the conventional LEDs without it. Inverted zinc oxide photonic-crystal structures were fabricated from polystyrene sphere template using the sol-gel solution of ZnO by spin-coating method. The inverted ZnO photonic-crystal structures observed show the tendency of the hexagonal compact arrangement formation. The resulting structures possess the photonic band gaps in the near-ultraviolet (NUV) range and exhibit an enhanced photoluminescence spectrum.