We have developed a new class of ladder-type dithienosilolo-carbazole (DTSC ), dithienopyrrolo-carbazole (DTPC ) and dithienocyclopenta-carbazole (DTCC ) units in which two outer thiophene subunits are covalently fastened to the central 2,7-carbazole cores by silicon, nitrogen and carbon bridges, respectively. The heptacyclic multifused monomers were polymerized with the benzothiadiazole (BT ) acceptor by palladium-catalyzed cross-coupling to afford three alternating donor-acceptor copolymers PDTSCBT , PDTCCBT  and PDTPCBT . The devices based on PDTSCBT  and PDTCCBT  exhibited high hole mobilities of 0.073 and 0.110 cm2 V-1s-1 with good on-off ratio of 1.1 � 106 and 1.7 � 104, respectively. The bulk heterojunction photovoltaic device using PDTSCBT  as the p-type material delivered a promising efficiency of 5.2% with a Voc of 0.82 V, a Jsc of 11.1 mA/cm2, a FF of 56.7%. The embedded silole units to effectively lower the HOMO energy level of PDTSCBT  are responsible for the highest Voc value of the device.

Carbazole-based heptacyclic arenes with carbon, silicon, and nitrogen bridges: Synthesis, molecular properties and photovoltaic applications

243rd National Meeting (2012)

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