Abstract: Squaraines have been promising donor materials because of their strong and broad absorption band in the visible and near infrared regions which is suitable for application in organic photovoltaic (OPV) cells. Two unsymmetrical squaraines (USQs), namely BIBISQ and TIBISQ, with two electron-donating aryls directly linked to the electron-withdrawing squaric acid core (Y-manner) could act as high performance donor materials for solution-processed bulk-heterojunction OPV cells. Both of two USQs show ideal low bandgaps (1.47 eV for BIBISQ and 1.39 eV for TIBISQ) with an intense and broad absorption band in the range of 500-900 nm, and relatively low HOMO levels of ~ -5.10 eV. The BHJ-OPV based on both of them simultaneously show excellent Jsc (over 13 mA cm-2), Voc (0.84V), FF (0.49) and PCEs of over 5% under the blend ratio of USQs:PC71BM=1:3. These results are indicating that the two USQs are quite promising candidates for small molecular (SM) OPV and the Y-manner should be quite perspective linked method for USQs.

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