Diketopyrrolopyrrole based small molecules with near infrared absorption for solution processed organic solar cells

•Two new small molecules with DPP as core unit were reported.•The two molecules gave optical bangap as low as 1.40 eV.•The two molecules exhibited wide absorption ranging from 300 to 900 nm.

Two small molecules DOR2TDPP and DCAO2TDPP with a diketopyrrolopyrrole (DPP) unit as the central building block have been designed and synthesized for solution-processed bulk-heterojuntion (BHJ) solar cells. The two molecules in films exhibited broad absorption ranging from 300 to 900 nm with optical bandgaps of around 1.40 eV. The BHJ solar cell devices based on the DOR2TDPP and DCAO2TDPP as donors and PC71BM as acceptors gave a PCE of 2.05% and 1.09%, respectively, under the illumination of AM.1.5G, 100 mW cm−2. The influence of blend ratio of donor/acceptor and amount of additive on the performance of the solar cell were studied systematically.

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