Arrays of TiO2 nanosphere monolayer on GaN-based LED for the improvement of light extraction

Abstract

We report on the fabrication of TiO2 nanospheres (NSs) monolayer arrays for enhancement of light extraction quantum efficiency of GaN-based light-emitting diodes (LEDs). The fabricated TiO2 NSs monolayer arrays composed of different phases of anatase (An-) and amorphous (Am-) TiO2, the arrays were transferred onto the topmost layer of LED chips via facile icing transfer method. The LED chips covered with Am-TiO2 NSs monolayer arrays shows 3.0- times enhanced light output power intensity compared with reference LED chips at a fixed injection current of 100 mA. The enhanced light extraction of LED chips by Am-TiO2 NSs monolayer can be attributed to an high transmittance (91.1%) in visible and increased light extraction probability of photons generated in LEDs, resulting from the enhanced light coupling efficiency by reduced total internal reflection (TIR). Finite-difference time-domain (FDTD) simulation results also agreed well with the experimentally observed results. Based on the experimental and theoretical results, our suggested Am- and An-TiO2 NSs arrays can be considered as a very facile and effective method to improve the device performance of various visible LEDs chips.