Abstract
The development of a high-performance polymer PBDT-BT for bulk heterojunction solar cell devices is summarized. The polymer was first synthesized by Stille polycondensation, and solar cell devices in conventional geometry were optimized through the use of a lithium salt cathode interlayer reaching 6% power conversion efficiency. Improvements were made to the synthesis of the polymer using Suzuki polycondensation giving high-molecular weight material in the M-n = 100 kg/mol range. Further device optimization in inverted geometry gave power conversion efficiency of over 9%. The synthesis scalability as well as the batch-to-batch reproducibility of the polymer were extensively investigated.