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

Abstract 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.