Low HOMO isoindigo based small molecule for high open-circuit voltage 1.0 V solution processed organic solar cells

• Isoindigo-based compound is synthesized.
• The solar cells device shows high open-circuit voltage of 1.0 V.
• Small molecule solar cells device is solution-processing.

One isoindigo and triphenylamine (TPA) based small molecule was synthesized by Suzuki coupling reaction. The obtained molecule was characterized by 1H NMR 13C NMR and MS. The obtained molecule absorbs light from 400 to 743 nm in thin solid film. The band-gaps of the resulting molecule calculated from the absorption onset and cyclic voltammetry are respectively around 1.67 eV and 1.60 eV. Photovoltaic cell by using the blend of the obtained small molecule and [6,6]-phenyl-C61 butyric acid methyl ester (PCBM) as an active layer was fabricated by spin-coating method. The solar cells show open-circuit voltage (Voc) of 1.0 V with maximum power conversion efficiency 0.61%. This high open-circuit voltage is among the highest in literatures for solution processed small molecule organic solar cells.

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