Novel Strategy for Constructing High Efficiency OLED Emitters with Excited State Quinone‐Conformation Induced Planarization Process

Abstract

In contrast to the common intramolecular charge transfer (ICT) emission, planarized intramolecular charge transfer (PLICT) based materials usually possess higher proportion radiative decay for their flat and rigid conformation in excited states. Herein, a strategy for designing PLICT‐based emitters by the excited state quinone‐conformation induced planarization is proposed. By virtue of RIR mechanism on TPP (tetraphenylpyrazinyl) unit, the newcomers named as TPP‐PPI (1‐phenyl‐2‐(4′‐(3,5,6‐triphenylpyrazin‐2‐yl)‐[1,1′‐biphenyl]‐4‐yl)‐1H‐phenanthro[9,10‐d] imidazole) and TPP‐PI (1‐phenyl‐2‐(4‐(3,5,6‐triphenylpyrazin‐2‐yl)phenyl)‐1H‐phenanthro[9,10‐d]imidazole) exhibit aggregation‐induced emission (AIE) characteristics. TPP‐PPI and TPP‐PI have obvious PLICT properties via series of spectral measurements. Employing theoretical calculation in ground and excited states in different solvents, their PLICT process is confirmed further, and TPP's contribution on PLICT formation becomes clear. In non‐doped organic light‐emitting diodes, these two emitters with AIE and PLICT characteristic exhibit good performance with external quantum efficiency (4.85% and 4.36%) as blue emitters.