title: Tuning the optoelectronic properties of nonfullerene electron acceptors.
abstract: Broad spectral coverage over the solar spectrum is necessary for photovoltaic technologies and is a focus for organic solar cells. We report a series of small-molecule, nonfullerene electron acceptors containing the [(benzo[c][1,2,5]thiadiazol-4-yl)methylene]malononitrile unit as a high electron affinity component. The optoelectronic properties of these molecules were fine-tuned with the objective of attaining strong absorption at longer wavelengths by changing the low-ionization-potential moiety. The electron-accepting function of these materials was investigated with poly(3-n-hexylthiophene) (P3HT) as a standard electron donor. Significant photocurrent generation in the near infrared region, with an external quantum yield reaching as high as 22 % at 700 nm and an onset >800 nm was achieved. The results support efficient hole transfer to P3HT taking place after light absorption by the acceptor molecules. A Channel II-dominated power conversion efficiency of up to 1.5 % was, thus, achieved.
authors.affiliation: Centre for Organic Photonics & Electronics, The University of Queensland, Brisbane QLD 4072 (Australia).
authors.forename: Yuan
authors.initials: Y
authors.lastname: Fang
authors.forename: Ajay K
authors.initials: AK
authors.lastname: Pandey
authors.forename: Dani M
authors.initials: DM
authors.lastname: Lyons
authors.forename: Paul E
authors.initials: PE
authors.lastname: Shaw
authors.forename: Scott E
authors.initials: SE
authors.lastname: Watkins
authors.forename: Paul L
authors.initials: PL
authors.lastname: Burn
authors.forename: Shih-Chun
authors.initials: SC
authors.lastname: Lo
authors.forename: Paul
authors.initials: P
authors.lastname: Meredith
keywords: energy conversion; materials science; organic electronics; solar cells; thin films