title: Spectral-distortion-free light extraction from organic light-emitting diodes using nanoscale photonic crystal.
abstract: Despite their generally good performance, photonic crystal (PC)-based organic light-emitting diodes (OLEDs) encounter a serious spectral distortion problem. In this study, we obtained spectral-distortion-free PC-based OLEDs by lowering the pitch (period of the PC) to less than a half the emission wavelength, using a simple and scalable nanoscale process of laser interference lithography. The demonstrated OLEDs with 200 nm pitch-size nanoscale periodic hole arrays exhibited negligible changes in the Internal Commission on Illumination 1931 color coordinate of Δ (0.0104, 0.0078) and a peak wavelength of Δ0 nm (relative to the reference), while maintaining the function of the internal light extraction layer, manifested as a 23% enhancement of the external quantum efficiency (EQE). The enhancement of the EQE reached 85% after incorporating a micro-lens array. The improved light extraction, spectral-distortion-free characteristic, and excellent color stability over a broad range of viewing angles were successfully derived by performing finite difference time domain simulations.
authors.affiliation: Display and Nanosystem Laboratory, College of Engineering, Korea University, Seoul 136-713, Korea.
authors.forename: Yong Sub
authors.initials: YS
authors.lastname: Shim
authors.forename: Kyu Nyun
authors.initials: KN
authors.lastname: Kim
authors.forename: Ju Hyun
authors.initials: JH
authors.lastname: Hwang
authors.forename: Cheol Hwee
authors.initials: CH
authors.lastname: Park
authors.forename: Sun-Gyu
authors.initials: SG
authors.lastname: Jung
authors.forename: Young Wook
authors.initials: YW
authors.lastname: Park
authors.forename: Byeong-Kwon
authors.initials: BK
authors.lastname: Ju