Synthesis and properties of hole-transporting fluorene linked bistriphenylamine

An amorphous hole-transporting material, 2,7-bis(4-diphenylaminophenyl)-9,9-bis-n-hexylfluorene (DAF), was synthesized by Suzuki cross-coupling reaction. DAF showed UV–vis absorption bands at 301 and 370 nm in dichloromethane solution and the photoluminescence spectrum showed a maximum peak at 426 nm in a purplish blue region. Cyclic voltammetry (CV) and differential scanning calorimetry (DSC) analysis revealed that DAF was an electrochemically stable amorphous material. It was fabricated as HTL with the device configuration of ITO/DAF/Alq3/LiF:Al. A bright green emission from Alq3 layer with a maximum brightness of 6500 cd/m2 was observed at 15 V and a low turn-on voltage of 3.8 V.