A crystalline D-π-A organic small molecule with naphtho[1,2-b:5,6-b′]dithiophene-core for solution processed organic solar cells

► A new naphtho[1,2-b:5,6-b′]dithiophene containing D-A organic small molecule, NDT(TTz)2 was designed and synthesized. ► The small molecule NDT(TTz)2 shows crystalline feature at room temperature with energy levels well-matched with PC71BM. ► Solution processed organic solar cells based on NDT(TTz)2 as a donor afforded a PCE up to ∼1.44% in preliminary trials.