title: Isoindigo-Containing Molecular Semiconductors: Effect of Backbone Extension on Molecular Organization and Organic Solar Cell Performance.
abstract: We have synthesized three new isoindigo-based small molecules by extending the conjugated length through the incorporation of octyl-thiophene units between the isoindigo core and benzothiophene terminal units. Both UV-vis and Grazing incidence X-ray diffraction experiments show that such extension of the π-conjugated backbone can induce H-aggregation, and enhance crystallinity and molecular ordering of these isoindigo-based small molecules in the solid state. Compared to two other isoindigo-based derivatives in the series, the derivative with two octyl-thiophene units, BT-T2-ID, is the most crystalline and ordered, and its molecular packing motif appears to be substantially different. Devices utilizing these new extended isoindigo-based small molecules as the electron donor exhibit higher performance than those utilizing nonextended BT-ID as the electron donor. Particularly, devices containing BT-T2-ID in an as-cast blend with PC61BM show power conversion efficiencies up to 3.4%, which is comparable to the best devices containing isoindigo-based molecular semiconductors and is a record among devices containing isoindigo-based small molecules that were processed in the absence of any additives.
authors: Department of Chemical and Biological Engineering, Princeton University , Princeton, New Jersey 08544, United States ; Princeton Center for Complex Materials, Princeton University , Princeton, New Jersey 08544, United States.
authors: Yi
authors: Y
authors: Ren
authors: Department of Chemical and Biological Engineering, Princeton University , Princeton, New Jersey 08544, United States.
authors: Anna K
authors: AK
authors: Hailey
authors: Department of Chemical and Biological Engineering, Princeton University , Princeton, New Jersey 08544, United States.
authors: Anna M
authors: AM
authors: Hiszpanski
authors: Department of Chemical and Biological Engineering, Princeton University , Princeton, New Jersey 08544, United States ; Princeton Center for Complex Materials, Princeton University , Princeton, New Jersey 08544, United States.
authors: Yueh-Lin
authors: YL
authors: Loo