Application of Small Molecule Donor Materials Based on Phenothiazine Core Unit in Bulk Heterojunction Solar Cells

A D-π-A type small molecule PTZ1 and an A-π-D-π-A type small molecule PTZ2 with phenothiazine as the central building block and dicyanovinyl as the electron-withdrawing end-group have been designed and synthesized. Compared with D-π-A type donor material PTZ1, the donor material PTZ2 with A-π-D-π-A configuration shows much wider response to solar light. The donor material PTZ1 possesses more positive highest occupied molecular orbital level, and higher V_oc was obtained for devices with PTZ1/PC71BM blend as the active layer. An improved efficiency of 3.25% was obtained for the PTZ2/PC71BM based solar cells.