T-shaped (D)2–A–π–A type sensitizers incorporating indoloquinoxaline and triphenylamine for organic dye-sensitized solar cells

Four novel T-shaped metal-free organic sensitizers QX22–25 based on triphenylamine and indoloquinoxaline have been successfully designed and synthesized as a (D)2–A–π–A type structure. These dye sensitizers have two triphenylamine donors attaching on an indoloquinoxaline-based subordinate acceptor. Different π-bridges (thiophene and furan) and acceptor/anchoring groups (cyanoacrylic acid and 2-(1,1-dicyanomethylene)rhodanine) were involved to tune the photoelectrical properties. Their optical, electrochemical, and photovoltaic properties as well as the DFT calculations have been systematically investigated, indicating these four dyes are all capable as photosensitizers. A highest power conversion efficiency up to 7.09% with a Jsc of 12.9 mA cm−2 and a Voc of 817 mV has been achieved by the dye QX23 with a furan π-bridge and a cyanoacrylic acid acceptor/anchoring group, indicating it is a promising strategy to construct efficient (D)2–A–π–A type sensitizers by incorporating indoloquinoxaline and triphenylamine.