Naphthalenothiophene Imide-Based Polymer Donor for High-Performance Polymer Solar Cells

Naphthalenothiophene imide (NTI), bearing six-membered imide and a five-membered aromatic ring, was synthesized by a one-step Suzuki reaction in high yield. NTI is an electron-deficient monomer that could effectively lower the HOMO energy level of the polymer. Thus, the NTI-based polymer PNTB1 has a low-lying HOMO energy level (−5.42 eV) without introducing any F or Cl group into the polymer backbone. By mixing with a nonfullerene electron acceptor Y6, solar cell devices exhibit power conversion efficiency as high as 15.18%. Because of the high efficiency of the NTI-based polymer and avoidance of multi-step synthesis of introducing other electron-accepting groups into the polymer chain, the electron-deficient NTI is a promising building unit for high-performance polymer donors.