Ultra-deep-blue thermally actrivated delayed fluorescence emitters constructed by carbazole derivatives enable efficient solution-processed OLED with a CIEy of < 0.05

Abstract

Thermally activated delayed fluorescence (TADF) emitters that satisfy the blue gamut of the BT.2020 standard have rarely been reported, severely hindering the application of TADF in full-color ultra-high definition (UHD) displays. Herein, three solution-processable ultra-deep-blue TADF emitters, namely BFCz-TDBA, ICz-TDBA and PIdCz-TDBA, were cleverly designed and synthesized by linking a rigid and symmetric oxygen-bridged boron acceptor directly to carbazole derivative donors with different strengths. All these TADF emitters exhibited ultra-deep-blue photoluminescence below 430 nm with a narrow full-width-at-half-maximum of less than 50 nm. Furthermore, their favorable solubility and thermal stability make them suitable for solution processing. The resultant solution-processed ultra-deep-blue organic light-emitting diodes (OLEDs) based on all the emitters exhibited a maximum external quantum efficiency of 12.0%, 13.0% and 12.2% for BFCz-TDBA, ICz-TDBA and PIdCz-TDBA, respectively. Correspondingly, their related Commission Internationale de l’Eclairage (CIE) chromaticity coordinates were (0.16, 0.044), (0.16, 0.049) and (0.16, 0.046), respectively, which represent the state-of-the-art deep-blue emission among solution-processed devices (CIE_y < 0.05). The typical BT.2020 blue gamut of these materials demonstrate their enormous potential for application in UHD displays.