Multifunctional quinoxaline containing small molecules with multiple electron-donating moieties: Solvatochromic and optoelectronic properties

Abstract

Two multifunctional quinoxaline containing small molecules (designated as: SD-1 and SD-2) composed of electron-donating (D) moieties both in vertical and horizontal directions to an electron-accepting (A) quinoxaline at the central position have been synthesized. In both SD-1 and SD-2, the dimethylaminobenzene (DMAB) and triphenylamine (TPA) groups were used as an electron-donor in the vertical direction, and dihexyloxy-functionalized TPA was adapted as an additional donor in the horizontal direction. The unique donor (D)-acceptor (A) structures around the central quinoxaline moiety impart special solvatochromic and optoelectronic features to the SD-1 and SD-2. Photovoltaic cells (PVCs) and organic light-emitting diodes (OLEDs) were fabricated from SD-1 and SD-2 by solution processing (i.e. spin-coating). While PVCs with a structure of ITO/PEDOT:PSS/SD-1 or SD-2:PC71 BM/Al show the power conversion efficiencies of 0.31% and 0.45%, respectively, OLEDs with a structure of ITO/PEDOT:PSS/SD-1 or SD-2/LiF/Al exhibit a maximum luminance (efficiency) of 7.42 cd/m(2) (0.034 cd/A) and 48.84 cd/m(2) (0.032 cd/A) with a turn-on voltage of 3.6 and 2.4 V. respectively. Furthermore, the Commission Internationale de L'Eclairage (CIE) chromacity coordinates of the OLED device with SD-2 were (0.67, 0.32), which are very close the CIE chromacity coordinates (0.67, 0.33) of National Television Society Committee (NTSC) for red color. Owing to their promising stimuli-responsive properties and device performances, these D-A molecules with unique structures can be considered as good candidates for multifunctional sensory and optoelectronic applications.