title: Tightly Bound Double-Caged [60]Fullerene Derivatives with Enhanced Solubility: Structural Features and Application in Solar Cells.
abstract: A series of novel highly soluble double-caged [60]fullerene derivatives were prepared by means of lithium-salt-assisted [2+3] cycloaddition. The bispheric molecules feature rigid linking of the fullerene spheres through a four-membered cycle and a pyrrolizidine bridge with an ester function CO2R (R=n-decyl, n-octadecyl, benzyl, and n-butyl; compounds 1 a-d, respectively), as demonstrated by NMR spectroscopy and X-ray diffraction. Cyclic voltammetry studies revealed three closely overlapping pairs of reversible peaks owing to consecutive one-electron reductions of fullerene cages, as well as an irreversible oxidation peak attributed to abstraction of an electron from the nitrogen lone-electron pair. Owing to charge delocalization over both carbon cages, compounds 1 a-d are characterized by upshifted energies of frontier molecular orbitals, a narrowed bandgap, and reduced electron-transfer reorganization energy relative to pristine C60. Neat thin films of the n-decyl compound 1 a demonstrated electron mobility of (1.3±0.4)×10-3cm2V-1s-1, which was comparable to phenyl-C61-butyric acid methyl ester (PCBM) and thus potentially advantageous for organic solar cells (OSC). Application of 1 in OSC allowed a twofold increase in the power conversion efficiencies of as-cast poly(3-hexylthiophene-2,5-diyl) (P3HT)/1 devices relative to the as-cast P3HT/PCBM ones. This is attributed to the good solubility of 1 and their enhanced charge-transport properties - both intramolecular, owing to tightly linked fullerene cages, and intermolecular, owing to the large number of close contacts between the neighboring double-caged molecules. Test P3HT/1 OSCs demonstrated power-conversion efficiencies up to 2.6 % (1 a). Surprisingly low optimal content of double-caged fullerene acceptor 1 in the photoactive layer (≈30 wt %) favored better light harvesting and carrier transport owing to the greater content of P3HT and its higher degree of crystallinity.
authors.affiliation: Chemistry Department, Lomonosov Moscow State University, Leninskie Gory, 1-3, 119991, Moscow, Russia.
authors.forename: Victor A
authors.initials: VA
authors.lastname: Brotsman
authors.affiliation: Chemistry Department, Lomonosov Moscow State University, Leninskie Gory, 1-3, 119991, Moscow, Russia.
authors.forename: Vitaliy A
authors.initials: VA
authors.lastname: Ioutsi
authors.affiliation: Chemistry Department, Lomonosov Moscow State University, Leninskie Gory, 1-3, 119991, Moscow, Russia.
authors.forename: Alexey V
authors.initials: AV
authors.lastname: Rybalchenko
authors.affiliation: Chemistry Department, Lomonosov Moscow State University, Leninskie Gory, 1-3, 119991, Moscow, Russia.
authors.forename: Vitaliy Yu
authors.identifier: http://orcid.org/0000-0003-4452-4087
authors.initials: VY
authors.lastname: Markov
authors.affiliation: Chemistry Department, Lomonosov Moscow State University, Leninskie Gory, 1-3, 119991, Moscow, Russia.
authors.forename: Nikita M
authors.initials: NM
authors.lastname: Belov
authors.affiliation: Chemistry Department, Lomonosov Moscow State University, Leninskie Gory, 1-3, 119991, Moscow, Russia.
authors.forename: Natalia S
authors.identifier: http://orcid.org/0000-0003-4017-8930
authors.initials: NS
authors.lastname: Lukonina
authors.affiliation: Chemistry Department, Lomonosov Moscow State University, Leninskie Gory, 1-3, 119991, Moscow, Russia.
authors.forename: Sergey I
authors.identifier: http://orcid.org/0000-0003-1663-0341
authors.initials: SI
authors.lastname: Troyanov
authors.affiliation: Chemistry Department, Lomonosov Moscow State University, Leninskie Gory, 1-3, 119991, Moscow, Russia.
authors.forename: Ilya N
authors.initials: IN
authors.lastname: Ioffe
authors.affiliation: Faculty of Physics & International Laser Center, Lomonosov Moscow State University, Leninskie Gory, 1-62, 119991, Moscow, Russia.
authors.forename: Vasiliy A
authors.initials: VA
authors.lastname: Trukhanov
authors.affiliation: Faculty of Physics & International Laser Center, Lomonosov Moscow State University, Leninskie Gory, 1-62, 119991, Moscow, Russia.
authors.forename: Galina K
authors.initials: GK
authors.lastname: Galimova
authors.affiliation: Faculty of Physics & International Laser Center, Lomonosov Moscow State University, Leninskie Gory, 1-62, 119991, Moscow, Russia.
authors.forename: Artur A
authors.initials: AA
authors.lastname: Mannanov
authors.affiliation: Institute of Nanotechnology of Microelectronics RAS, Leninsky Prospekt, 32A, 119991, Moscow, Russia.
authors.forename: Dmitry N
authors.initials: DN
authors.lastname: Zubov
authors.affiliation: Institut für Chemie, Humboldt Universität zu Berlin, Brook-Taylor-Strasse 2, 12489, Berlin, Germany.
authors.forename: Erhard
authors.identifier: http://orcid.org/0000-0002-5300-3905
authors.initials: E
authors.lastname: Kemnitz
authors.affiliation: Chemistry Department, Lomonosov Moscow State University, Leninskie Gory, 1-3, 119991, Moscow, Russia.
authors.forename: Lev N
authors.initials: LN
authors.lastname: Sidorov
authors.affiliation: Chemistry Department, Lomonosov Moscow State University, Leninskie Gory, 1-3, 119991, Moscow, Russia.
authors.forename: Tatiana V
authors.initials: TV
authors.lastname: Magdesieva
authors.affiliation: Faculty of Physics & International Laser Center, Lomonosov Moscow State University, Leninskie Gory, 1-62, 119991, Moscow, Russia.
authors.forename: Dmitry Yu
authors.identifier: http://orcid.org/0000-0002-9156-0657
authors.initials: DY
authors.lastname: Paraschuk
authors.affiliation: Chemistry Department, Lomonosov Moscow State University, Leninskie Gory, 1-3, 119991, Moscow, Russia.
authors.forename: Alexey A
authors.identifier: http://orcid.org/0000-0003-4460-5370
authors.initials: AA
authors.lastname: Goryunkov
keywords: X-ray diffraction; cage compounds; cyclic voltammetry; fullerenes; photochemistry