title: Linking the HOMO-LUMO gap to torsional disorder in P3HT/PCBM blends.
abstract: The electronic structure of [6,6]-phenyl C61 butyric acid methyl ester (PCBM), poly(3-hexylthiophene) (P3HT), and P3HT/PCBM blends is studied using soft X-ray emission and absorption spectroscopy and density functional theory calculations. We find that annealing reduces the HOMO-LUMO gap of P3HT and P3HT/PCBM blends, whereas annealing has little effect on the HOMO-LUMO gap of PCBM. We propose a model connecting torsional disorder in a P3HT polymer to the HOMO-LUMO gap, which suggests that annealing helps to decrease the torsional disorder in the P3HT polymers. Our model is used to predict the characteristic length scales of the flat P3TH polymer segments in P3HT and P3HT/PCBM blends before and after annealing. Our approach may prove useful in characterizing organic photovoltaic devices in situ or even in operando.
authors.affiliation: College of Nano Science and Technology, Soochow University, 199 Ren-Ai Rd., Suzhou, Jiangsu 215123, China.
authors.forename: John A
authors.initials: JA
authors.lastname: McLeod
authors.affiliation: Department of Physics and Engineering Physics, University of Saskatchewan, 116 Science Place, Saskatoon, Saskatchewan S7N 5E2, Canada.
authors.forename: Amy L
authors.initials: AL
authors.lastname: Pitman
authors.affiliation: Institute of Metal Physics, Russian Academy of Sciences-Ural Division, 620990 Yekaterinburg, Russia.
authors.forename: Ernst Z
authors.initials: EZ
authors.lastname: Kurmaev
authors.affiliation: Institute of Metal Physics, Russian Academy of Sciences-Ural Division, 620990 Yekaterinburg, Russia.
authors.forename: Larisa D
authors.initials: LD
authors.lastname: Finkelstein
authors.affiliation: Ural Federal University, 620002 Yekaterinburg, Russia.
authors.forename: Ivan S
authors.initials: IS
authors.lastname: Zhidkov
authors.affiliation: Molecular Electronics and Photonics Research Unit, Department of Mechanical Engineering and Materials Science and Engineering, Cyprus University of Technology, Kitiou Kiprianou St. 45, 3603 Limassol, Cyprus.
authors.forename: Achilleas
authors.initials: A
authors.lastname: Savva
authors.affiliation: Department of Physics and Engineering Physics, University of Saskatchewan, 116 Science Place, Saskatoon, Saskatchewan S7N 5E2, Canada.
authors.forename: Alexander
authors.initials: A
authors.lastname: Moewes
mesh_terms: D004583:Electrons; D037741:Fullerenes / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry*; D011789:Quantum Theory; D013876:Thiophenes / Q000737:chemistry*
chemical_list: C539575:(6,6)-phenyl C61-butyric acid methyl ester; D037741:Fullerenes; D011108:Polymers; D013876:Thiophenes; C000588862:poly(3-hexylthiophene-2,5-diyl)