Affiliation:
1. Department of Organic Materials Science Graduate School of Organic Materials Science Yamagata University 4-3-16 Jonan Yonezawa Yamagata 992-8510 Japan
2. Research Center for Organic Electronics (ROEL) Yamagata University 4-3-16 Jonan Yonezawa Yamagata 992-8510 Japan
3. Frontier Center for Organic Materials (FROM) Yamagata University 4-3-16 Jonan Yonezawa Yamagata 992-8510 Japan
4. Department of Applied Chemistry Graduate School of Science and Engineering Ehime University 790-8577 Matsuyama Japan
Abstract
AbstractAlthough λ5‐phosphinine derivatives are known as a promising class of blue fluorescent emitters, those photoluminescent quantum yield (PLQY) values have been reached up to 92 %, however, only a few examples have been explored as an emitter for blue organic light‐emitting device (OLED), and the external quantum efficiency (EQE) has been below 2.4 % so far. In this study, we newly developed two types of blue λ5‐phosphinine derivatives namely CN‐COCF3 and CO2Me‐CHO, and investigated the photophysical properties in the solid states. The photophysical analyses in solid state films suggested that the strong electron‐accepting nature of these λ5‐phosphinine derivatives caused the inferior PLQY values, and the exciplex formation with the host and neighboring materials should be avoided to improve the device efficiency. By choosing suitable host and neighboring materials with deep ionization potentials, we successfully realized efficient blue fluorescent OLEDs with EQE of over 4 % and CIE (0.14, 0.18). This is among the best in λ5‐phosphinine‐based blue OLEDs so far.
Funder
Japan Science and Technology Corporation