Novel Blue Bipolar Thermally Activated Delayed Fluorescence Material as Host Emitter for High‐Efficiency Hybrid Warm‐White OLEDs with Stable High Color‐Rendering Index

• Published in: Advanced functional materials 2018-04, Vol.28 (17), p.n/a
• Main Authors: Liang, Jie, Li, Chenglong, Zhuang, Xuming, Ye, Kaiqi, Liu, Yu, Wang, Yue
• Format: Article
• Language: English
• Subjects: Chemical synthesis; Diodes; Efficiency; Electroluminescence; Emitters; Fluorescence; Förster energy transfer; high color rendering index (CRI); hybrid white OLEDs; Materials science; nondoped blue devices; Organic light emitting diodes; Performance indices; Phosphorescence; Power efficiency; Quantum efficiency; Rendering; thermally activated delayed fluorescence (TADF)
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.201707002

A novel thermally activated delayed fluorescence (TADF) molecule, PHCz2BP, is synthesized and used to construct high performance organic light‐emitting diodes (OLEDs) in this work. PHCz2BP is not only the neat emitting layer for efficient sky‐blue OLED, with very high peak external quantum efficiency/power efficiency (EQE/PE) values of 4.0%/6.9 lm W−1, but also acts as a host to sensitize high‐luminance and high‐efficiency green, orange, and red electrophosphorescence with the universal high EQEs of >20%. More importantly, two hybrid white OLEDs based on the double‐layer emitting system of PHCz2BP:green phosphor/PHCz2BP:red phosphor are achieved. To the best of the knowledge, this is the first report for three‐color (blue–green–red) white devices that adopt a TADF blue host emitter and two phosphorescent dopants without any other additional host. Such simple emitting systems thus realized the best electroluminescent performance to date for the WOLEDs utilizing the hybrid TADF/phosphor strategy: forward‐viewing EQEs of 25.1/23.6% and PEs of 24.1/22.5 lm W−1 at the luminance of 1000 cd m−2 with the color rendering indexes of 85/87 and warm‐white Commission Internationale de L'Eclairage coordinates of (0.41, 0.46)/(0.42, 0.45), indicating its potential to be used as practical eye‐friendly solid‐state lighting in future. A novel blue thermally activated delayed fluorescence (TADF) host emitter realizes two simple three‐color white organic light‐emitting diodes with the best TADF/phosphor hybrid white electroluminescent performance to date: forward‐viewing external quantum efficiencies of 25.1/23.6% and power efficiencies of 24.1/22.5 lm W−1 at the luminance of 1000 cd m−2 with the high color rendering indexes of 85/87.