Abstract
Four small molecule electron acceptors TEH-PDI, TEH-DPDI, TPDI and TDPDI based on a porphyrin core and perylene bisimides (PDI) units were designed and synthesized. The energy levels and aggregation properties of the four acceptors were tuned to match those of a porphyrin electron donor C19OD-DPP based on a porphyrin core and 1,4-diketopyrrolo[3,4-c]pyrroles (DPP) end groups by adjusting the number of PDI units and the connection manners to a porphyrin core synergistically. The all-porphyrin bulk heterojunction (BHJ) solar cells exhibit panchromatic photon-to-current conversion from 300 to 900 nm with a small valley around 650 nm and provide power conversion efficiencies (PCEs) of 0.11%–2.57% when the active layers were prepared in the presence of octane-1,8-dithiol (ODT) additive. Further investigations show that more balanced hole/electron mobility, less trap-assisted monomolecular recombination and bimolecular recombination are beneficial for achieving higher Jsc and PCE for C19OD-DPP/TPDI devices.
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