Blue light-emitting and hole-transporting materials based on 9,9-bis(4-diphenylaminophenyl)fluorenes for efficient electroluminescent devices

Abstract

New bifunctional materials namely BTTF, TPTF and BPTF having 9,9-bis(4-diphenylaminophenyl)fluorene as a molecular platform were synthesized and characterized. These molecules showed strong blue emission in both solution and solid state with a solution fluorescence quantum efficiency of up to 74% and were thermally stable amorphous materials with glass transition temperature well above 170 °C. The abilities of these materials as blue light-emitting materials for blue OLEDs and hole-transporting materials for green OLEDs in terms of device performance and thermal property were superior to a commonly used N,N′-diphenyl-N,N′-bis(1-naphthyl)-(1,1′-biphenyl)-4,4′-diamine (NPB). Efficient non-doped blue and Alq3-based green OLEDs with maximum luminance efficiencies and CIE coordinates of 2.06 cd A⁻¹ and (0.15, 0.13), and 4.94 cd A⁻¹ and (0.29, 0.52) were achieved, respectively, with BPTF having two pyrene substituents as the emitting layer and the hole-transporting layer, respectively.