Star-shaped chromophores based on a benzodithiophene fused truxene core for solution processed organic solar cells

• A truxene based planar electron-rich core was designed and synthesized.
• A series of star-shaped chromophores with various terminal groups were prepared.
• Organic solar cells based on the chromophores exhibit Voc in the range of 0.86–1.07 V.
• The best power conversion efficiency of 2.40% has been achieved.

By fusing three benzodithiophenes with a truxene, a new planar aromatic electron-rich core was synthesized, which was used for the construction of novel star-shaped chromophores with various terminal groups. The absorption maxima of the synthesized star-shaped chromophores in thin film are varied from 366 nm to 527 nm depending on the electron donating/accepting properties of the terminal groups. Bulk heterojunction (BHJ) photovoltaic devices were fabricated by using the star-shaped chromophores as donor materials and (6, 6)-phenyl C71-butyric acid methyl ester (PC71BM) as an acceptor material. The fabricated solar cells showed open circuit voltages (Voc) in the range of 0.86–1.07 V, which are related with the energy difference between HOMO energy levels of the chromophores and the LUMO energy level of PC71BM. BHJ photovoltaic devices based on one of these star-shaped chromophores exhibit a power conversion efficiency of 2.40% without extended optimization.

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