Molecular Donor–Acceptor Dyads for Efficient Single‐Material Organic Solar Cells

Single-material organic solar cells (SMOSCs) promise several advantages withrespect to prospective applications in printed large-area solar foils. Only onephotoactive material has to be processed and the impressive thermal and pho-tochemical long-term stability of the devices is achieved. Herein, a novel structuraldesign of oligomeric donor–acceptor (D–A) dyads 1–3 is established, in which anoligothiophene donor and fullerene acceptor are covalently linked by a exiblespacer of variable length. Favorable optoelectronic, charge transport, andself-organization properties of the D–A dyads are the basis for reaching powerconversion efciencies up to 4.26% in SMOSCs. The dependence of photovoltaicand charge transport parameters in these ambipolar semiconductors on thespecic molecular structure is investigated before and after post-treatment bysolvent vapor annealing. The inner nanomorphology of the photoactive lms ofthe dyads is analyzed with transmission electron microscopy (TEM) and grazing-incidence wide-angle X-ray scattering (GIWAXS). Combined theoretical calculationsresult in a lamellar supramolecular order of the dyads with a D–A phase separationsmaller than 2 nm. The molecular design and the precise distance between donorand acceptor moieties ensure the fundamental physical processes operative inorganic solar cells and provide stabilization of D–A interfaces