Oligothiophene based small molecules with a new end group for solution processed organic photovoltaics

• A new terminal group named INER was synthesized by merging other two groups together.
• Two small molecules with INER as the terminal group were designed and synthesized for organic solar cells.
• Both molecules show broad and red-shift absorption with very narrow band gaps.

Two oligothiophene based small molecules (DINER5T and DINER7T) with a new end group INER were synthesized as the donors for organic solar cells, and their photovoltaic performance was studied and compared with the corresponding compounds (DRHD7T and DIN7T) with the same backbone structure but different end groups. Both of the new molecules exhibit broad and red shift absorption compared with DRHD7T and DIN7T, with very low band gaps of 1.47 eV and 1.34 eV, respectively. The devices based on DINER5T:PC71BM and DINER7T:PC71BM blend films gave PCEs of 4.22% and 4.02%, respectively, through a solvent vapor annealing (SVA) process with CH2Cl2.

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