Near-infrared response thienoisoindigo-based small molecule for solution-processed bulk-heterojunction solar cells

5'-Hexyl-2,2'-bithiophene end-capped thienoisoindigo-based small molecule (TIDO2T) is synthesized by Stille coupling reaction. The TIDO2T exhibits good solubility in common organic solvents such as THF, toluene, dichlorobenzene and chloroform. The UV-vis absorption spectrum of TIDO2T shows wide absorption between 427 nm and 871 nm in thin solid film, and the optical band-gap calculated from absorption onset was 1.42 eV. Bulk heterojunctions (BHJ) solar cell was fabricated with TIDO2T as the donor and 6,6-phenyl-C-61-butyric acid methyl ester (PC61 BM) as the acceptor by simple solution spin-coating processing. The device obtained a power conversion efficiency of 1.14% with V-OC 0.44V, J(SC) 7.76 mA cm(-2) and FF 33% under AM 1.5G solar simulator. The external quantum efficiency (EQE) curve extends to near-infrared region (around 900-1000 nm). (C) 2013 Elsevier B.V. All rights reserved.