Conjugated silole and carbazole copolymers : Synthesis, characterization, single-layer light-emitting diode, and field effect carrier mobility

Soluble conjugated random and alternating copolymers (PCz-PSP) derived from N-hexyl-3,6-carbazole (Cz) and l,l-dimethyl-2,3,4,5-tetraphenylsilole (PSP) were synthesized by palladium(0)-catalyzed Suzuki coupling reactions. The feed ratios of Cz to PSP were 95:5, 90:10, 80:20, 70:30, and 50:50. Chemical structures and optoelectronic properties of the copolymers were characterized by 1 H NMR, 13 C NMR, UV absorption, cyclic voltammetry, photoluminescence, electroluminescence, and field effect transistor. HOMO levels of the copolymers are between -5.15 and -5.34 eV. Single-layer devices with a configuration of ITO/copolymer/Ba/Al were fabricated and the copolymer with PSP content of 20% displayed the highest external quantum efficiency of 0.77%. Field effect transistors with tantalum pentoxide-polyacrylonitrile double insulators demonstrated that hole mobilities of the copolymers decreased with their PSP contents, and the hole mobility up to 9.3 x 10 -6 cm 2 . (V .s) -1 could be achieved.

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