Facile solvothermal synthesis of high refractive index ZrO2 spheres: estimation of the enhanced light extraction efficiency

摘要

Sub-micron sized ZrO2 spheres were synthesized by a facile solvothermal reaction method. The influence of Zr(OPr)(4) concentration on the size and size distribution of ZrO2 spheres were examined by taking the scanning electron microscope and transmission electron microscope images. When the concentration of Zr(OPr)(4) was increased from 0.031 to 0.045 mol, the average size of the spheres also increased from 305 to 920 nm. The diffused reflectance spectra of the calcined ZrO2 spheres exhibited the higher reflectivity than that of as-prepared ZrO2 spheres. As compared to the bare LEDs, light extraction efficiency was improved to 23% when the ZrO2 spheres were coated on the ITO surface, however, 70.12% was improved when the ZrO2 spheres were coated on the GaN surface due to the spherical morphology induced photon escape cone enhancement.