A new D–A–π–A type organic sensitizer based on substituted dihydroindolo [2,3-b] carbazole and DPP unit with a bulky branched alkyl chain for highly efficient DSCs

Two new D–A–π–A configuration metal-free organic sensitizers (T1–T2) based on 5,7-dihexyl-6,12-diphenyl-5,7-dihydroindolo[2,3-b]carbazole and a DPP unit with a bulky branched alkyl chain have been synthesized for dye-sensitized solar cells. Due to a bulky branched alkyl chain being attached to the donor and DPP unit, both compounds obtain high Voc values. Under standard global AM 1.5 solar light conditions, the T1 based-device gives a high conversion efficiency of 8.24% with a Jsc of 15.72 mA cm−2, a Voc of 0.74 V and a FF of 0.71. These excellent performances make the donor dihydroindolo[2,3-b] carbazole and DPP unit promising candidates for further application in DSCs.