Open AccessEnhancement of light-extraction efficiency of organic light-emitting diodes using silica nanoparticles embedded in TiO_2 matrices
Author(s) -
Jooyoung Lee,
Yun Young Kwon,
Eun-Ho Choi,
JeongWoo Park,
Hong Yoon,
Hyunbin Kim
Publication year - 2014
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.22.00a705
Subject(s) - chemical mechanical planarization , materials science , oled , diode , optoelectronics , layer (electronics) , refractive index , nanoparticle , light emitting diode , finite difference time domain method , light scattering , substrate (aquarium) , extraction (chemistry) , optics , scattering , nanotechnology , oceanography , physics , geology , chemistry , chromatography
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.