High efficiency solution processed OLEDs using a thermally activated delayed fluorescence emitter

Highly efficient solution processed organic light-emitting devices (OLEDs) incorporating a thermally activated delayed fluorescent (TADF) emitter are developed. As a green emitter, we used 1,2,3,5-tetrakis (carbazol-9-yl)-4,6-dicyanobenzene (4CzIPN). As an electron transporting layer (ETL), we used phenylpyridine-based wide-energy gap materials. These ETLs have high triplet energy over 2.7 eV, relatively high electron mobility of 10(-4) cm(2) V-1 s(-1), and high hole blocking ability to effectively confine all the excitons and carriers in the emissive layer. A solution processed OLED with a structure of [ITO (130 nm)/PEDOT:PSS (30 nm)/4CzIPN 5 wt% doped 4,4'-N,N'-dicarbazolylbiphenyl (CBP) (35 nm)/bis-4,6-(3,5-di-4-pyridylphenyl)-2-methylpyrimidine (B4PyMPM) (65 nm)/8-quinolinolato lithium (Liq) (3 nm)/Al (100 nm)] were fabricated. This device showed a very low turn-on voltage of 2.5 V at 1 cd m(-2) with a maximum power efficiency of over 55 lm W-1. These performances are highest values reported in solution processed TADF OLEDs so far. (C) 2015 Elsevier B.V. All rights reserved.