Use of benzothiadiazole-triphenylamine amorphous polymer for reproducible performance of polymer-fullerene bulk-heterojunction solar cells

An amorphous polymer, poly(BTD-TPA), which consists of benzothiadiazole and triaryl-amine units, can be successfully utilized to fabricate bulk heterojunction (BHJ) organic photovoltaics (OPVs), and the OPV performance can be demonstrated to be independent of the casting solvent or thermal annealing temperature. The OPV based on poly(BTD-TPA):PC70BM (1:4) that was fabricated using chloroform (boiling point of 61 degrees C) and annealed at 60 degrees C for 10 min exhibited a power conversion efficiency (PCE) of 2.81% under simulated solar irradiation through an air mass of 1.5 at 100 mW cm (2). On the other hand, the OPV fabricated using o-dichlorobenzene (boiling point of 181 degrees C) and annealed at 110 degrees C for 10 min exhibited a PCE of 2.65%. Almost the same PCEs and incident photon to current conversion efficiencies (IPCEs) were obtained in both OPVs. The use of an amorphous film of poly(BTD-TPA) in the fabrication of OPVs offers great advantages over the use of a polycrystalline film of regioregular poly(3-hexylthiophene) (P3HT) in terms of high reproducibility of the OPV performance. (c) 2012 Elsevier B.V. All rights reserved.