Donor-acceptor-donor ?-conjugated material derived from merocyanine-diketopyrrolopyrrole: design, synthesis and photovoltaic applications

In this work, two diketopyrrolopyrrole based donors (DPP3 and DPP4) with an electron rich merocyanine as a side arm conjugating with the electron-accepting DPP through different linking groups such as phenyl and thiophene, respectively. As a result DPP4, which is linked with thiophene, possesses significant red-shifted absorption. BHJ solar cells were fabricated using DPP3 and DPP4 as donor materials and the commercially available PC61BM as an acceptor moiety. It was observed that DPP4 gave less power conversion efficiency (0.4%) but higher short-circuit current (JSC) 1.88 mA/cm2 than the DPP3 with 0.48% power conversion efficiency with 1.72 mA/cm2 JSC. Our results suggest that the optical and electrochemical properties and photovoltaic performance of the DPP based BHJ devices can be influenced by the rational design of the DPP donor unit with merocyanine linkers.