Naphthalene Diimide-Based Ionenes as Universal Interlayers for Efficient Organic Solar Cells.

Self-doping ionone polymers were efficiently synthesized by reacting functional naphthalene diimide (NDI) with 1,3-dibromopropane ( NDI-NI ) or trans-1,4-dibromo-2-butene ( NDI-CI ) via quaternization polymerization. These NDI-based ionene polymers are universal interlayers with random molecular orientation, boosting the efficiencies of fullerene-based, non-fullerene-based, and ternary organic solar cells (OSCs) over a wide range of interlayer thicknesses, with maximum efficiency of 16.9%. NDI-NI showed higher interfacial dipole (Δ), conductivity and electron mobility than NDI-CI, affording solar cells with higher efficiencies. These polymers proved to efficiently lower the work function ( WF ) of air stable metal and optimize the contact of metal electrode and organic semiconductor, highlighting their power to overcome energy barriers of electron injection and extraction process for efficient organic electronics.