Multiple charge transfer disk-like emitters with fast fluorescence radiation rate and high horizontal dipole orientation for pure blue organic light-emitting diodes

作者：Gan, Yiyang; Peng, Xiaomei; Qiu, Weidong; Wang, Liangying; Li, Deli; Xie, Wentao; Liu, Denghui; Li, Mengke; Lin, Jianying; Su, Shi-Jian^*

来源：Chemical Engineering Journal, 2022, 430: 133030.

DOI：10.1016/j.cej.2021.133030

• Pure blue OLEDs
• Multiple charge transfer
• Disk-like structure
• High radiative transition rates
• Horizontal dipole orientation

The efficiency of pure blue Organic light-emitting diodes (OLEDs) still needs to be improved, which is limited by the utilization of the forbidden transition triplet excitons and low light-out-coupling efficiency in devices. Herein, two blue emitters were developed through combining multiple diphenylamine (DPA) donors with an oxygenbridged boron (DBA) or triphenyl triazine (TRZ) acceptor. Notably, a narrow-band deep blue emission with a peak of 423 nm and a Full-width at half-maximum (FWHM) of 34 nm is realized for the boron-based emitter in toluene solution. Thanks to their multiple Charge transfer (CT) channels and high orientated disk-like structure, high radiative transition rates (kr > 108 s-1) and high horizontal emitting dipole ratios (Theta > 80%) can be realized simultaneously. Meanwhile, the introduction of the peripheral DPA units can also provide multiple localized triplet (3LE) states for spin up-conversion of forbidden transition triplet excitons. Owing to the effective upconversion of triplet excitons and high light-out-coupling efficiency, maximum external quantum efficiency of more than 10% is achieved for the boron emitter-based pure blue OLEDs with a Commission Internationale de l'Eclairage (CIE) coordinates of (0.14, 0.08).