Solution-processible perylene diimide based star-shaped small molecule acceptor: Synthesis and photovoltaic properties

Previously we have reported a series of perylene dimide (PDI) dimers as efficient solution-processible small molecule acceptors. In this paper we present a new solution-processible PDI trimer with triphenylamine as the romatic bridge. This trimer was synthesized by Suzuki coupling reaction and fully characterized with H-1-NMR, C-13-NMR, TOF-MS, and elementary analysis. It exhibits a broad absorption band in the wavelength range from 450 to 650 nm with a peak round 533 nm and a maximum extinction coefficient of 9.61 x 10(4) M-1 cm(-1). Its lowest unoccupied and highest occupied molecular orbit (LUMO and HOMO) energies are -3.75 and -5.60 eV. When blend with the commercial P3HT, it gives an open-circuit voltage (V-oc) of 0.73 V, a short-circuit current-density (J(sc)) of 0.60 mA/cm(2), a fill-factor (FF) of 51.0% and an efficiency of 0.22%. When utilizing the conjugated polymer of PBDTTT-C-T as the donor and 5% DIO as the additive, the best conventional cell yields 1.82% efficiency with a V-oc of 0.99 V, a Jsc of 3.44 mA/cm(2), and an FF of 53.0%.