Cruciform DPVBi: synthesis, morphology, optical and electroluminescent properties

Abstract

4,4′-Bis(2,2-diphenylvinyl)-1,1′-biphenyl (DPVBi) is a well-known blue-emitting material for electroluminescent devices, but its vacuum evaporated films exhibit a phase transition trend from amorphous to crystalline state, which impacts morphological stability and device lifetime. We report here a cruciform DPVBi derivate, named 2,5,2′,5′-tetrakis(2,2-diphenylvinyl)biphenyl (TDPVBi), in which two 1,4-bis(2,2-diphenylvinyl)benzene segments are linked through a central biphenyl linkage. TDPVBi exhibits very high photoluminescence efficiency in the solid state (80%), and fully amorphous characteristics with high glass transition temperature (T_g = 110 °C). High performance non-doped blue organic light-emitting device (OLED) with Commission Internationale de I'Eclairage (CIE) coordinates of (0.16, 0.21), maximum luminance efficiency of 6.2 cd A⁻¹ (corresponding external quantum efficiency of 3.8%), and maximum luminance exceeding 31 170 cd m⁻² is achieved based on TDPVBi. The operation lifetime of TDPVBi-based device exhibits a 1.7-fold enhancement relative to that of a similar device based on DPVBi.