High Open-Circuit Voltage Solar Cells Based on New Thieno[3,4-<i>c</i>]pyrrole-4,6-dione and 2,7-Carbazole Copolymers

Abstract

New alternating copolymers derived from thieno[3,4-c]pyrrole-4,6-dione (TPD) and 2,7-carbazole moieties have been synthesized by Suzuki cross-coupling reaction and characterized. These polymers combine interesting properties such as good solubility and excellent thermal and air stability. The present studies indicate that the combination of TPD and 2,7-carbazole building blocks can be a very effective way to lower the HOMO energy level and ultimately to enhance the Voc of polymer solar cells. The Voc reported here (up to 1.07 V) is one of the highest observed for polymer:[60]PCBM bulk heterojunction devices, and preliminary results on the photovoltaic devices (power conversion efficiencies up to 1.8%) indicate that performance could probably be improved by increasing the molecular weights and by fine-tuning the electronic properties and the morphology.