Two BDT-TPP-Based Polymer Semiconductors: It’s Characterization and Application for Photovoltaics

Novel conjugated polymers composed of benzodithiophene (BDT) unit and new acceptor TPP group, which has alkoxyphenyl substituent on thienopyrroledione (TPD) unit, were designed and synthesized. Two conjugated polymers have different side chains on BDT units and were applied to solar cell devices. OBDT-TPP with linear alkoxy side chain on the BDT unit showed a power conversion efficiency (PCE) of 1.55%, while EBDT-TPP with branched alkoxy side chains exhibited an increased PCE of 2.07%. UV-visible absorption and cyclic voltammetry measurements reveal that the different side chains on BDT unit have little influences on the optical band gap and the energy levels of the polymers. However, the XRD studies and hole mobility measurement exhibited increased polymer crystallinity and hole carrier mobility in EBDT-TPP:PC₇₁BM blends. These results lead to slight increase in PCE of solar cell with EBDT-TPP.