Acene‐Modified Small‐Molecule Donors for Organic Photovoltaics

We design and synthesize a series of acene-modified small molecules and investigate their photovoltaic characteristics by using the small molecules in organic photovoltaics (OPVs). We introduce different cores to modulate the conjugation lengths of the small molecules and the bulk heterojunction (BHJ) morphologies. Three small-molecule donors are made, namely Ph-TTR, Na-TTR, and An-TTR, having phenyl, naphthalene, and anthracene moieties, respectively, as conjugated cores. These donors were synthesized in a few steps and exhibited favorable BHJ morphologies, thereby giving promising power conversion efficiencies (PCEs). The donors showed excellent miscibility with the acceptor PC71BM, and the use of the additive 1,8-diiodooctane (DIO) led to a remarkable increase in crystallinity, thereby increasing the PCEs of their OPVs. Of the three donors, Na-TTR showed the most efficient charge carrier generation and favorable molecular packing structures; and hence of the three types of devices tested, the Na-TTR:PC71BM devices exhibited the highest PCE, specifically 6.27%, without pre- or post-treatments. The promising PCEs achieved from these easily synthesized acene-modified small molecules suggested that acene-modified small molecules can be useful materials in OPVs.