Deep-blue fluorescent emitter based on a 9,9-dioctylfluorene bridge with a hybridized local and charge-transfer excited state for organic light-emitting devices with EQE exceeding 8

It is indispensable to synthesize deep-blue light emitting materials with high luminous efficiency for realizing full-colour organic light emitting diode (OLED) displays. The hybridized local and charge-transfer (HLCT) state is a special excited state that hybridizes the local state and the charge transfer state to ensure a high fluorescence quantum yield ( η pl ). Herein, a blue fluorescent material of TPA-DFCP was designed and synthesized, with a twisted D-π-A configuration, in which triphenylamine (TPA), benzonitrile (CP) and 9,9-dioctylfluorene serve as the D, A, and π-conjugation unit, respectively. It also exhibits good solubility and can be dissolved in several organic solvents with different polarities. The non-doped device, with TPA-DFCP as the emitter, shows excellent electroluminescent (EL) efficiency with a maximum EQE of 7.74%. Furthermore, the doped device of TPA-DFCP exhibits excellent deep-blue emission with the EL emission peak at 436 nm and the CIE coordinates at (0.153, 0.077), which are very close to the NTSC standard blue CIE ( x , y ) coordinates of (0.140, 0.080). Meanwhile, the doped device also exhibited excellent EL performance, with a maximum external quantum efficiency (EQE) and radiative exciton utilization ( η r ) of 8.30% and 57.67%, respectively. The doped device of TPA-DFCP exhibits excellent deep-blue emission with the EL emission peak at 436 nm and the CIE coordinates at (0.153, 0.077), and excellent EL performance with a maximum external quantum efficiency (EQE) of 8.30%.