Efficient and Multifunctional Electroluminescent Ultra Deep‐Blue Material with Hybrid Localization and Charge Transfer

Hybrid local and charge transfer (HLCT) emitters have received much attention because they can utilize triplet exciton via hot exciton channels. However, exploiting novel multifunctional deep‐blue HLCT materials capable of high color purity remains a great challenge. Herein, two deep‐blue emitters with HLCT properties, PdCz‐2CN and mPdCz‐2CN, aresynthesized. The non‐doped OLED based on PdCz‐2CN or mPdCz‐2CN emitter with EQEmax and Commission Internationale de l'Eclairage (CIE) coordinates Y values of 5.42%@0.062 and 2.05@0.064, respectively. More importantly, the doped‐OLEDs achieve ultra deep‐blue emission with EQEmax and CIEy values of 5.10%@0.037 and 1.96%@0.050, respectively, which is close to the BT.2020 standard. In addition, the PdCz‐2CN can not only obtain ultra‐deep blue OLED, but also realize the exciplex‐OLED as the electron acceptor for realizing multifunctional luminescence. As a result, the non‐doped exciplex OLED based on PdCz‐2CN: 15 wt.%TAPC as the luminescent layer achieves 15.44% EQEmax via forming green exciplex emission with hole transport layer TAPC. Moreover, PdCz‐2CN: 15 wt.%TAPC exciplex‐based as the host, red phosphor Ir(MDQ)2(acac) as the guest of OLED reaches red emission, and the EQEmax isup to 20.14%. This study is the first deep‐blue HLCT emitter using picolinonitrile as an electron acceptor, having significant potential for efficient exciplex OLED applications.