Two conjugated acceptor–p–donor–p–acceptor (A–p–D–p–A) small molecules with a zinc porphyrin
donor core and 3-ethylrhodanine terminal acceptors connected at the meso positions by ethynylene
groups and linked by one or two thienylenevinylene units denoted by 1a and 1b were synthesized and
their optical and electrochemical properties were investigated. Bulk heterojunction organic solar cells
fabricated with 1a : PC71BM and 1b : PC71BM processed with THF exhibited power conversion efficiencies
of 2.75% (Jsc ¼ 7.96 mA cm_x0002_2, Voc ¼ 0.96 V and FF ¼ 0.36) and 3.18% (Jsc ¼ 8.84 mA cm_x0002_2, Voc ¼ 0.90
V and FF ¼ 0.40), respectively. Moreover, organic solar cells based on 1a : PC71BM and 1b : PC71BM
processed with pyridine/THF solution displayed PCEs of 5.27% (Jsc ¼ 10.61 mA cm_x0002_2, Voc ¼ 0.92 V and
FF ¼ 0.54) and 5.78% (Jsc ¼ 11.58 mA cm_x0002_2, Voc ¼ 0.86 V and FF ¼ 0.58), respectively. However, most
important is the observation that the PCE was further increased to 7.24% for devices based on
1a : PC71BM and 1b : PC71BM active layers processed with pyridine/THF solution by employing CuSCN as
a selective contact electrode instead of the most common hole transport material, namely, PEDOT:PSS.