Molecular Consideration for Small Molecular Acceptors Based on Ladder‐Type Dipyran: Influences of O‐Functionalization and π‐Bridges

Abstract Molecular engineering of nonfullerene acceptors (NFAs) plays a vital role in the development of organic photovoltaics. Oxygen as an electron donating atom is incorporated into the NFA system as alkoxyl forms at central, terminal, or central conjugated moieties due to the tunability at structural conformation, solubility, electron donating ability, absorption, energy levels, etc. In this work, a novel dipyran‐based ladder‐type building block (Ph‐DTDP), which possesses two oxygen atoms in the conjugated skeleton, is designed and facilely synthesized. It is applied as the donor core for the acceptor–donor–acceptor‐type NFA design and such functionalized‐O efficiently enhances the electron donating ability, lowers the band gap, redshifts and extends the absorption spectra. In addition, the π‐bridge effects are considered as well. Photovoltaic performances are systematically investigated and a high power conversion efficiency of 9.21% can be afforded with an energy loss of 0.57 eV. Meanwhile, the morphologies as well as the carrier mobilities of the blend films are studied to assist further understanding of the structure–property relationships. Overall, the study in this work provides a new promising ladder‐type dipyran building block and brings in a novel way to use oxygen in NFA molecular structure design.