Multifunctional Bipolar Materials Serving as Emitters for Efficient Deep-Blue Fluorescent OLEDs and as Hosts for Phosphorescent and White OLEDs

摘要

Blue luminescent materials are always highly desired for organic light-emitting diodes (OLEDs) but the electroluminescence (EL) performances for most blue emitters still need to be improved in both efficiency and stability. In this work, four bipolar molecules with twisted donor-acceptor structures (PIPD-MP-DPA, PIPD-MP-IMDB, PIPD-MP-DMAC, and PIPD-MP-DPAC) are designed and synthesized. These molecules possess good thermal and electrochemical stabilities, and exhibit strong deep-blue photoluminescence. Their non-doped OLEDs show deep-blue EL emissions at 418-438 nm, and high maximum external quantum efficiencies (eta(ext,max)) of up to 4.4% with a CIEy value of only 0.078. Furthermore, the phosphorescent OLEDs (PhOLEDs) based on PIPD-MP-DPA host achieve excellent eta(ext,max) of 25.9% and 28.0% for green and orange, respectively, with small efficiency roll-offs. In addition, PIPD-MP-DPA is also employed to construct hybrid white OLEDs (WOLEDs), giving high eta(ext,max) of 21.6% for two-color WOLEDs, and 16.3% for four-color WOLEDs. In brief, these bipolar materials reveal outstanding EL performances in deep-blue fluorescent, phosphorescent, and hybrid white OLEDs, indicating huge potential applications in display and lighting techniques.