Key Laboratory of Modern Acoustics and Department of Materials Science and Engineering, Nanjing University, Nanjing 210093, China.
Nanoscale. 2014 Jul 21;6(14):8177-84. doi: 10.1039/c4nr01065e.
TiO₂ nanoparticle layers composed of columnar TiO₂ nanoparticle piles separated with nanoscale pores were fabricated on the bottom surface of the hemispherical glass prism by performing gas phase cluster beam deposition at glancing incidence. The porosity as well as the refractive index of the nanoparticle layer was precisely tuned by the incident angle. Effective extraction of the light trapped in the substrate due to total internal reflection with the TiO₂ nanoparticle layers was demonstrated and the extraction efficiency was found to increase with the porosity. An enhanced Rayleigh scattering mechanism, which results from the columnar aggregation of the nanoparticles as well as the strong contrast in the refractive index between pores and TiO₂ nanoparticles in the nanoporous structures, was proposed. The porous TiO₂ nanoparticle coatings were fabricated on the surface of GaN LEDs to enhance their light output. A nearly 92% PL enhancement as well as a 30% EL enhancement was observed. For LED applications, the enhanced light extraction with the TiO₂ nanoparticle porous layers can be a supplement to the microscale texturing process for light extraction enhancement.
通过在掠入射气相团束沉积条件下，在半球形玻璃棱镜的下表面制备了由柱状 TiO₂ 纳米颗粒堆积体分隔开的纳米级孔的 TiO₂ 纳米颗粒层，该层具有纳米多孔结构。通过调节入射角可以精确调整纳米颗粒层的孔隙率和折射率。实验证明，TiO₂ 纳米颗粒层可以有效提取由于全内反射而被困在基底中的光，并且发现提取效率随孔隙率的增加而增加。提出了一种增强的瑞利散射机制，该机制源于纳米颗粒的柱状聚集以及纳米多孔结构中孔和 TiO₂ 纳米颗粒之间的折射率的强烈对比。在 GaN LED 的表面制备了多孔 TiO₂ 纳米颗粒涂层以增强其光输出。观察到将近 92%的 PL 增强和 30%的 EL 增强。对于 LED 应用，TiO₂ 纳米颗粒多孔层的增强光提取可以作为微结构纹理化工艺的补充，以增强光提取。
