Developing high-performance polymer donors are highly demanded to fulfil the potential of the layer-by-layer (LBL) processed organic solar cells (OSCs). In this study, we present an effective method to develop...

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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.