title: Enhancement of light-extraction efficiency of organic light-emitting diodes using silica nanoparticles embedded in TiO₂ matrices.
abstract: We investigate two types of internal light-extraction layer structures for organic light-emitting diodes (OLEDs) that consist of silica nanoparticles (NPs) embedded in high-refractive-index TiO₂ matrices. The composite of silica NPs and TiO₂ matrices was coated on the glass substrate and fabricated with and without a SiO₂ planarization layer. An increase in the optical out-coupling efficiency by a factor of 2.0 was obtained at a high luminance of 3,000 cd/m² from OLEDs containing the silica NPs embedded in TiO₂ matrices between glass substrates and Zn-doped In₂O₃ (IZO) electrodes after additional planarization processes. This is consistent with the analytical result using the finite-difference time-domain (FDTD) method. Randomly distributed silica NPs acting as scattering centers could reduce the optical loss when extracting light. By using additional planarization processes with a PECVD-derived SiO₂ layer, one can assure that smoother surfaces provide higher out-coupling efficiency, which attain 100% and 97% enhancements in power (lm/W) and current (cd/A) efficiencies, respectively.
authors.forename: Jooyoung
authors.initials: J
authors.lastname: Lee
authors.forename: Yun Young
authors.initials: YY
authors.lastname: Kwon
authors.forename: Eun-Ho
authors.initials: EH
authors.lastname: Choi
authors.forename: JeongWoo
authors.initials: J
authors.lastname: Park
authors.forename: Hong
authors.initials: H
authors.lastname: Yoon
authors.forename: Hyunbin
authors.initials: H
authors.lastname: Kim