High Open-Circuit VoltageSolar Cells Based on New Thieno[3,4-c]pyrrole-4,6-dioneand 2,7-Carbazole Copolymers.

New alternating copolymers derived from thieno[3,4-c]pyrrole-4,6-dione (TPD) and 2,7-carbazole moieties havebeen synthesized by Suzuki cross-coupling reaction and characterized.These polymers combine interesting properties such as good solubilityand excellent thermal and air stability. The present studies indicatethat the combination of TPD and 2,7-carbazole building blocks canbe a very effective way to lower the HOMO energy level and ultimatelyto enhance the Vocof polymer solar cells.The Vocreported here (up to 1.07 V) isone of the highest observed for polymer:[60]PCBM bulk heterojunctiondevices, and preliminary results on the photovoltaic devices (powerconversion efficiencies up to 1.8%) indicate that performance couldprobably be improved by increasing the molecular weights and by fine-tuningthe electronic properties and the morphology. [ABSTRACT FROM AUTHOR]