Efficient chemical structure and device engineering for achieving difluorinated 2,2′-bithiophene-based small molecular organic solar cells with 9.0% efficiency

Abstract

Three novel narrow band gap small molecules (SMs) with D(A–Ar)2 molecular frameworks, based on fluorinated 2,2′-bithiophene (FBT) as an electron-donating (D) central core coupled with different electron-acceptor (A) bridge units, and 2-octylthiophene (Ar) units as end-capping units, were designed and synthesized for application as donor materials in solution-processed SM-OSCs. Under optimized conditions, a high PCE of 9.00% with a very high Jsc of 16.14 mA cm−2 and a FF of 73.52% for FBT(TDPP-T)2/PC71BM is obtained in single layer OSCs, which is among the highest reported for D(A–Ar)2-type SM based solar cells with a PCE up to 9% so far.