Low band gap thienoisoindigo-based molecules for near-infrared organic photovoltaics

Novel near-infrared organic molecules (TII 1 and TII 2) based on D-π-A-π-D structure using di-p-tolylamine and carbazole as the electron donor, thiophene and benzene as the π-linker, and thienoisoindigo (TII) as the electron acceptor were synthesized and their photo-physical properties were characterized. The maximum absorption band of TII 1 and TII 2 located at 790 and 627 nm while the absorption onset was extended to 923 and 726 nm, respectively, which corresponding to the bandgap of 1.50 and 1.70 eV. The bulk heterojunction solar cell device fabricated by using TII 1/PC61BM and TII 2/PC61BM as the active layer exhibited a power conversion efficiency (PCE) of 0.02∼0.82%.