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Tightly Bound Double‐Caged [60]Fullerene Derivatives with Enhanced Solubility: Structural Features and Application in Solar Cells
Author(s) -
Brotsman Victor A.,
Ioutsi Vitaliy A.,
Rybalchenko Alexey V.,
Markov Vitaliy Yu.,
Belov Nikita M.,
Lukonitalia S.,
Troyanov Sergey I.,
Ioffe Ilya N.,
Trukhanov Vasiliy A.,
Galimova Galina K.,
Mannanov Artur A.,
Zubov Dmitry N.,
Kemnitz Erhard,
Sidorov Lev N.,
Magdesieva Tatiana V.,
Paraschuk Dmitry Yu.,
Goryunkov Alexey A.
Publication year - 2017
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.201700194
Subject(s) - fullerene , organic solar cell , solubility , chemistry , fullerene chemistry , homo/lumo , intermolecular force , delocalized electron , cycloaddition , intramolecular force , crystallography , materials science , molecule , photochemistry , stereochemistry , organic chemistry , polymer , catalysis
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 CO 2 R (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 C 60 . Neat thin films of the n ‐decyl compound 1 a demonstrated electron mobility of (1.3±0.4)×10 −3 cm 2 V −1 s −1 , which was comparable to phenyl‐C 61 ‐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.