Synthesis, characterization, and electroluminescent properties of indazole, pyrazole, and triazole/triphenylamine-based compounds.

In this work, seven small molecular compounds named N,N -diphenyl-4-(2-phenylpyrimido [1,2-b]indazol-4-yl)aniline (1) , N , N -diphenyl-4-(5-phenylpyrazolo [1,5- a pyrimidin-7-yl)aniline (2) , N , N -diphenyl-4-(5-phenyl- [1,2,4]triazolo [1,5- a pyrimidin-7-yl)aniline (3) , 4,4'-(pyrimido [1,2-b]indazole-2,4-diyl)bis (N,N -diphenylaniline) (4) , 4,4'-(pyrazolo [1,5- a pyrimidine-5,7-diyl)bis (N , N -diphenylaniline) (5) , 4,4'-([1,2,4]triazolo [1,5- a pyrimidine-5,7-diyl)bis (N , N -diphenylaniline) (6) , N , N -diphenyl-4-(4-phenylpyrimido [1,2-b]indazol-2-yl)aniline (7) with donor-acceptor (D-A) structure were designed and synthesized by employing triphenylamine (TPA) as donor and indazole, pyrazole and/or triazole as acceptor. Systematic study and analysis on thermal, photophysical, electrochemical properties of all compounds were performed. All compounds exhibit good thermal and morphological stabilities with decomposition temperatures (T d) range from 270 to 462 °C, and glass transition temperatures (T g) range from 78 to 127 °C. The investigation of photophysical properties of these compounds revealed that all these compounds are of high photoluminescence quantum yields (PLQY), particularly for compound 6 , whose PLQY value was as high as 90.22%. To explore potential applications of these materials in organic light-emitting diodes (OLEDs), two devices with compounds 2 and 5 were fabricated. Both devices show excellent device performances with maximum current efficiency, maximum power efficiency and external quantum efficiency of 15.9 cd A−1, 10.4 l m W-1 and 8.4% for compound 2- based device and 10.1 cd A−1, 5.8 l m W-1 and 5.5% for compound 5- based device, respectively. Image 1 • Seven D-A type EL materials with the hole-transporting unit TPA and three different azole electron-transporting units were synthesized • These bipolar host materials exhibited good thermal and morphological stabilities, as well as high photoluminescence quantum yields. • Two materials were selected for fabrication of red fluorescent OLED devices and exhibited excellent device performance. [ABSTRACT FROM AUTHOR]