Thermally stable red electroluminescent hybrid polymers derived from functionalized silsesquioxane and 4,7-bis(3-ethylhexyl-2-thienyl)-2,1,3-benzothiadiazole

• Published in: Journal of polymer science. Part A, Polymer chemistry Polymer chemistry, 2009-11, Vol.47 (21), p.5661-5670
• Main Authors: Xiao, Yang, Lu, Xuehong, Tan, Li-Wei, Ong, K.S, He, Chaobin
• Format: Article
• Language: English
• Subjects: Applied sciences; conjugated polymers; Current efficiency; Electric potential; Electroluminescence; Electronics; Exact sciences and technology; fluorescence; hyperbranched; Inorganic and organomineral polymers; Light-emitting diodes; luminescence; Optoelectronic devices; Physicochemistry of polymers; Polymerization; Polymers; POSS; Preparation; red; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Spectra; Thermal stability; Voltage
• ISSN: 0887-624X; 1099-0518; 1099-0518
• DOI: 10.1002/pola.23608

Hyperbranched organic-inorganic hybrid conjugated polymers P1 and P2 were prepared via FeCl₃-oxiditive polymerization of 4,7-bis(3-ethylhexyl-2-thienyl)-2,1,3-benzothiadiazole (A) and octa(3-ethylhexyl-2-thienyl-phenyl)polyhedral oligomeric silsesquioxane (POSS) (B) at different POSS concentrations. Compared to linear polymer PM derived from A, P1, and P2 exhibit much higher PL quantum efficiency (φPL₋f) in condensed state with improved thermal stability. φPL₋f of P1 and P2 increased by 80% and 400%, and the thermal degradation temperatures of P1 and P2 are increased by 35 °C and 46 °C, respectively. Light-emitting diodes were fabricated using P1, P2, and PM. While the electroluminescent spectra of both P1 and PM show λmax at 660 nm, P1 exhibits a much narrower EL spectrum and higher electroluminescence (~500%) compared with PM at a same voltage and film thickness. The maximum current efficiency of P1 is more than seven times of that of PM. The turn-on voltages of the LEDs are in the order of P2 > PM > P1. LED prepared by blending P1 with MEH-PPV shows a maximum luminescence of 2.6 x 10³ cd/m² and a current efficiency of 1.40 cd/A, which are more than twice (1.1 x 10³ cd/m²) and five times (0.27 cd/A) of LED of PM/MEH-PPV blend, respectively.