title: New low bandgap near-IR conjugated D-A copolymers for BHJ polymer solar cell applications.
abstract: We synthesized two novel ultra low bandgap donor-acceptor (D-A) copolymers (E(g) ≤ 1.2 eV), containing the thiadiazoloquinoxaline unit as the main electron accepting unit (A) and benzodithiophene (BDT) and dithienosilole (DTS) as different donor units (D), denoted as P1 and P2, respectively, using the cross-coupling Stille reaction. The copolymers possess light absorption ranging from UV (350 nm) to near-IR (1300 nm) with optical bandgaps of 1.16 eV and 1.08 eV, respectively. Quantum-chemical calculations and experimental data were compared for proposing a more detailed concept for the optical and electronic properties of these copolymers which can be used as donors for polymer solar cells (PSCs). The PSCs based on optimized P1:PC71BM and P2:PC71BM showed overall power conversion efficiencies (PCEs) of 4.32% and 3.48%, respectively. Although P2 possesses a broad absorption coverage of up to 1300 nm, the lower PCE may be attributed to the low J(sc), due to the poor driving force for exciton dissociation, since the LUMO offset with PC71BM is less than 0.3 eV. The PCE has been significantly increased to 7.27% and 6.68% for solvent vapor annealing (SVA) treated P1:PC71BM and P2:PC71BM active layers, respectively. This improvement arises from the appropriate nanoscale morphology and an increase in hole mobility, induced by the SVA treatment of the active layers.
authors.affiliation: Institute of Organoelement Compounds of the Russian Academy of Sciences, Vavilova St., 28, 119991 Moscow, Russian Federation. keshtov@ineos.ac.ru.
authors.forename: M L
authors.initials: ML
authors.lastname: Keshtov
authors.affiliation: Institute of Organoelement Compounds of the Russian Academy of Sciences, Vavilova St., 28, 119991 Moscow, Russian Federation. keshtov@ineos.ac.ru.
authors.forename: S A
authors.initials: SA
authors.lastname: Kuklin
authors.affiliation: Carl von Ossietzky University of Oldenburg, 26129, Oldenburg, Germany.
authors.forename: N A
authors.initials: NA
authors.lastname: Radychev
authors.affiliation: Institute of Organoelement Compounds of the Russian Academy of Sciences, Vavilova St., 28, 119991 Moscow, Russian Federation. keshtov@ineos.ac.ru.
authors.forename: A Y
authors.initials: AY
authors.lastname: Nikolaev
authors.affiliation: Lomonosov Moscow State University, Faculty of Physics, 1-2 Leninskiye Gory, Moscow 119991, Russian Federation.
authors.forename: I E
authors.initials: IE
authors.lastname: Ostapov
authors.affiliation: Institute of Organic Chemistry of the Russian Academy of Sciences, Leninsky Prospect 47, 119991 Moscow, Russian Federation.
authors.forename: M M
authors.initials: MM
authors.lastname: Krayushkin
authors.affiliation: Institute of Organoelement Compounds of the Russian Academy of Sciences, Vavilova St., 28, 119991 Moscow, Russian Federation. keshtov@ineos.ac.ru.
authors.forename: I O
authors.initials: IO
authors.lastname: Konstantinov
authors.affiliation: Nanotechnology and Advanced Materials Laboratory, Department of Chemical Engineering, University of Patras, Patras, 26500 GR, Greece and Molecular Engineering Laboratory, Department of Physics, University of Patras, Patras, 26500 GR, Greece.
authors.forename: E N
authors.initials: EN
authors.lastname: Koukaras
authors.affiliation: Department of Electronics and Communication Engineering, LNMIIT (Deemed University), Jamdoli, Jaipur (Raj.) 302031, India.
authors.forename: Abhishek
authors.initials: A
authors.lastname: Sharma
authors.affiliation: Molecular Electronics and Optoelectronics Research Laboratory, Department of Physics, LNMIIT (Deemed University), Jamdoli, Jaipur (Raj.) 302031, India. gdsharma273@gmail.com.
authors.forename: G D
authors.initials: GD
authors.lastname: Sharma