Highly Efficient Deep-Blue Electroluminescence from a A−π–D−π–A Structure Based Fluoresence Material with Exciton Utilizing Efficiency above 25%

Deep-blue fluorescence materials are considered to have great commercial potential in blue-light emitter for organic light-emitting diodes (OLEDs). Nonetheless, rare deep-blue fluorescence materials meet double requirements for Commission International de L′Eclairage (CIE) coordinates of (0.14, 0.08) according to National Television System Committee (NTSC) and high external quantum efficiency (EQE) above 5%. Herein, we report a novel type of deep-blue fluorescence material with twisting A−π–D−π–A structure, namely CzPAF-TFMP. Relative measurements and theoretical results reveal that deep-blue emission of CzPAF-TFMP originates from hybridized local excited (LE) state and charge transfer (CT) excited state. The OLED based on CzPAF-TFMP emitter realizes high quality deep-blue emission with a full width at half-maximum (fwhm) of only 47 nm and CIE coordinates of (0.155, 0.066), which is close to NTSC standard. Meanwhile, it possesses high EQE of 5.4% and high exciton utilizing efficiency (ηs) of 73.4%, surpassing conventional limit of 25% for fluorescence material. Moreover, the device also displays good color stability and little efficiency roll-off. Because of the good solubility and film-formation property, CzPAF-TFMP performs well in solution-processed OLED, indicating potential application in inkjet printing OLED.