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

A D-π-A type small molecule <b>PTZ1</b> and an A-π-D-π-A type small molecule <b>PTZ2</b> 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 <b>PTZ1</b>, the donor material <b>PTZ2</b> with A-π-D-π-A configuration shows much wider response to solar light. The donor material <b>PTZ1</b> possesses more positive highest occupied molecular orbital level, and higher <i>V</i>_oc was obtained for devices with <b>PTZ1</b>/<b>PC71BM</b> blend as the active layer. An improved efficiency of 3.25% was obtained for the <b>PTZ2</b>/<b>PC71BM</b> based solar cells.