Acceptor-Enhanced Local Order in Conjugated Polymer Films.
Disorder in conjugated polymers is a general drawback that limits their use in organic electronics. We show that an archetypical conjugated polymer, MEH-PPV, enhances its local structural and electronic order upon addition of an electronic acceptor, trinitrofluorenone (TNF). First, acceptor addition in MEH-PPV results in a highly structured XRD pattern characteristic for semicrystalline conjugated polymers. Second, the surface roughness of the MEH-PPV films increases upon small acceptor addition, implying formation of crystalline nanodomains. Third, the low-frequency Raman features of the polymer are narrowed upon TNF addition and indicate decreased inhomogeneous broadening. Finally, the photoinduced absorption and surface photovoltage spectroscopy data show that photoexcited and dark polymer intragap electronic states assigned to deep defects disappear in the blend. We relate the enhanced order to formation of a charge-transfer complex between MEH-PPV and TNF in the electronic ground state. These findings may be of high importance to control structural properties as they demonstrate an approach to increasing the order of a conjugated polymer by using an acceptor additive.
Olga D
OD
Parashchuk
§Institute of Physics, University of Siegen, Emmy-Noether-Campus, Walter-Flex-Strasse 3, D-57068 Siegen, Germany.
Souren
S
Grigorian
Eduard E
EE
Levin
Vladimir V
VV
Bruevich
Kirill
K
Bukunov
Ilya V
IV
Golovnin
#Helmholtz-Zentrum Berlin, Hahn-Meitner-Platz 1, 14109 Berlin, Germany.
Thomas
T
Dittrich
∇Shubnikov Institute of Crystallography of the Russian Academy of Sciences, Leninskii prospekt 59, 119333 Moscow, Russia.
Kirill A
KA
Dembo
∇Shubnikov Institute of Crystallography of the Russian Academy of Sciences, Leninskii prospekt 59, 119333 Moscow, Russia.
Vladimir V
VV
Volkov
Dmitry Yu
DY
Paraschuk
Raman spectroscopy; X-ray diffraction; atomic force microscopy; bulk heterojunction; charge-transfer complex; conjugated polymers; organic electronics