Lensfree OLEDs with over 50% external quantum efficiency via external scattering and horizontally oriented emitters

Abstract

High efficiency is important for successful deployment of any light sources. Continued efforts have recently made it possible to demonstrate organic light-emitting diodes with efficiency comparable to that of inorganic light-emitting diodes. However, such achievements were possible only with the help of a macroscopic lens or complex internal nanostructures, both of which undermine the key benefits of organic light-emitting diodes as an affordable planar light source. Here we present a systematic way to achieve organic light-emitting diodes with ultrahigh efficiency even only with an external scattering film, one of the simplest low-cost outcoupling structures. Through a global, multivariable analysis, we show that scattering with a high degree of forwardness has a potential to play a critical role in realizing ultimate efficiency. Combined with horizontally oriented emitters, organic light-emitting diodes equipped with particle-embedded films tailored for forward-intensive scattering achieve a maximum external quantum efficiency of 56%.

Unusually Fast Phosphorescence from Ir(III) Complexes via Dinuclear Molecular Design

“…As a result, complex 6 is an emitter with an emission rate a few times higher than other Ir(III) phosphors used in OLEDs. 10,14,17,19,21,23,[25][26][27][29][30][31][32] Moreover, by the emission rate, 6 also outcompetes the materials exhibiting thermally activated delayed fluorescence (TADF) [62][63][64][65][66][67][68] which are posed as alternative OLED emitters. 62,[69][70][71][72] The proposed di-nuclear design affords outstanding phosphorescence efficiency and also leaves room for photophysical tuning through modifications of the bridging C^NN^C ligand and N^C^N ligand and also through modifications at the position of the halogen anion.…”

“…6,8,9 Indeed, cyclometallated Pt(II) and Ir(III) complexes are often employed as emitters in phosphorescent OLEDs (PhOLEDs). 7,[10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] Apart from a high emission quantum yield, it is desirable that an OLED emitter shows a high radiative rate (short radiative decay time) in order to utilize more excitons per unit of time.…”

Interplay among work function, electronic structure and stoichiometry in nanostructured VOx films

“…The interest in organic semiconductors, has risen strongly because of high efficiency applications (e.g. OFET, OPV and OLED) 1,2 and for the eases of manipulation at industrial level. 3 Organic semiconductors do not have intrinsic charge carriers: these have to be supplied by electrodes, i.e., hole and electron injection layers.…”

Impact of Boron Acceptors on the TADF Properties of Ortho-Donor-Appended Triarylboron Emitters

“…OLED devices were fabricated on 25 × 25 mm glass substrate with half-patterned ITO layers (AMG). Glass substrates with pre-patterned ITO electrodes were cleaned by a sequential wet-cleaning processes in an ultrasonic bath (Song et al, 2018 ). After drying in a vacuum oven for a day, the substrates were subject to UV-plasma treatment for 1 min in a plasma cleaner (CUTE-MP, Femto Science).…”