Exceptionally efficient organic light emitting devices using high refractive index substrates

Abstract

Organic light emitting devices (OLEDs) are now used in commercial cell phones and flat screen displays, but may become even more successful in lighting applications, in which large area, high efficiency, long lifetime and low cost are essential. Due to the relatively high refractive index of the organic layers, conventional planar bottom emitting OLEDs have a low outcoupling efficiency. Various approaches for enhancing the optical outcoupling efficiency of bottom emitting OLEDs have been introduced in the literature. In this paper we demonstrate a green bottom emitting OLED with a record external quantum efficiency (42%) and luminous efficacy (183 lm/W). This OLED is based on a high index substrate and a thick electron transport layer (ETL) which uses electrical doping. The efficient light outcoupling is modeled by optical simulations. 3779-3781 (2003). 10. Y. Sun, and S. R. Forrest, "Enhanced light out-coupling of organic light-emitting devices using embedded lowindex grids," Nat. Photonics 2(8), 483-487 (2008). 11. T. Nakamura, N. Tsutsumi, N. Juni, and H. Fujii, "Thin-film waveguiding mode light extraction in organic electroluminescent device using high refractive index substrate," J. Appl. Phys. 97(5), 054505 (2005). 12. ©2009 Optical Society of America

The role of photonics in energy

“…[319][320][321] A variety of approaches for extracting wave-guided modes trapped in ITO/organic layers, such as PCs, corrugated grating substrates, and high-index substrates, have been demonstrated to enhance the light outcoupling efficiency. [322][323][324][325][326] Mie scattering supported by dielectric nanostructures and localized SPRs supported by metallic nanostructures are also effective at increasing the light extraction efficiency of light-emitting devices due to their large scattering cross sections. While these techniques are effective for extracting thin-film guided modes, they have their shortcomings.…”

Integrated optical model for organic light-emitting devices

“…For modeling of these two effects we use an ensemble of incoherent electrical dipole antennas with random orientation, 6,7 used in earlier work. [8][9][10][11] It is assumed that the OLED is a one-dimensional layer structure since its lateral dimensions (>1 mm) are much larger than its thickness ($1 lm). The emission of the dipole antenna is decomposed in plane and evanescent coherent waves with a transverse electric (TE) and transverse magnetic (TM) polarization.…”

Over 130 lm/W All-Phosphorescent White OLEDs for Next-generation Lighting

“…Many approaches have been proposed to improve the OCE using technologies such as scattering layers [5], corrugated substrates [6], out-coupling film [7], high refractive index substrates [8], and photonic crystals [9].…”