Tuning electronic properties of molecular acceptor-π-porphyrin-π-acceptor donors via π-linkage structural engineering

Abstract

Abstract Three new molecular A-π-D-π-A type donors, P1, P2 and P3, comprising an alkylthiothienyl substituted porphyrin electron donor core (D) and two 3-ethylrhodanine electron acceptor moieties (A) connected peripherally to the porphyrin core via respectively a monomeric, dimeric or trimeric phenylethynyl π-linkage, are synthesized and studied for their optoelectronic, charge transport, and photovoltaic properties. The hole mobilities of their blend films with PC71BM follow the order of P3> P2 > P1 in hole-only device. When used as electron donors with fullerene acceptor, PC71BM, in conventional bulk heterojunction organic solar cells, the optimal device with P1 donors shows a lower FF, but an intensity stronger and broader EQE, the highest JSC and VOC. As a whole, the PCEs of their optimal devices follow the order of P1> P2 > P3, corresponding to 8.61%, 8.20% and 7.82%, respectively. These results clearly demonstrate the decisive influence of π–linkage length over photovoltaic performance, and that the shorter the π–linkage length the better the photovoltaic performance.