Bis(carbazol-9-yl)phenyl end-caped polyaromatics as solution-processed deep blue fluorescent emitters for simple structure solution-processed electroluminescent devices

Abstract

Development of organic emitters, particularly blue color, is a crucial factor that impacts the extent of organic light emitting diodes (OLEDs) in panel display applications. As blue emitting materials are sparse but greatly desired for high efficiency performing devices, a series of different conjugated core organic small molecules fluorescent emitters (C-A-C, C-BA-C, C-PA-C, C-NA-C, C–P–C, and C-BP-C) have been designed and synthesized in this contribution for blue OLED application. The molecules are constructed from basic building blocks of blue chromophores (anthracene or pyrene derivatives) and end-capped with charge transporting (1,3-phenylene)bis(3,6-di-tert-butyl-9H-carbazole) units which provided the tunable emission in the blue spectral range. Their optical, electrochemical, photophysical, and thermal properties along with device performances were investigated systematically. The best device performance based on C-A-C as the emitter offered low turn on voltage of 3.7 V, external quantum efficiency of 3.24%, strong deep-blue emission (424 nm) with high color purity (FWHM = 59) at CIE coordinates x = 0.155, y = 0.066.