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Polymorphism in the 1:1 Charge‐Transfer Complex DBTTF–TCNQ and Its Effects on Optical and Electronic Properties
Author(s) -
Goetz Katelyn P.,
Tsutsumi Jun'ya,
Pookpanratana Sujitra,
Chen Jihua,
Corbin Nathan S.,
Behera Rakesh K.,
Coropceanu Veaceslav,
Richter Curt A.,
Hacker Christina A.,
Hasegawa Tatsuo,
Jurchescu Oana D.
Publication year - 2016
Publication title -
advanced electronic materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.25
H-Index - 56
ISSN - 2199-160X
DOI - 10.1002/aelm.201600203
Subject(s) - materials science , ambipolar diffusion , acceptor , x ray photoelectron spectroscopy , crystallography , tetracyanoquinodimethane , raman spectroscopy , charge transfer complex , spectroscopy , charge (physics) , organic semiconductor , electronic structure , chemical physics , electron , molecule , chemistry , photochemistry , computational chemistry , nuclear magnetic resonance , optoelectronics , condensed matter physics , organic chemistry , physics , quantum mechanics , optics
The organic charge‐transfer complex dibenzotetrathiafulvalene–7,7,8,8‐tetracyanoquinodimethane is found to crystallize in two polymorphs when grown by physical vapor transport: the known α‐polymorph and a new structure, the β‐polymorph. Structural and elemental analysis via selected area electron diffraction, X‐ray photoelectron spectroscopy, and polarized IR spectroscopy reveal that the complexes have the same stoichiometry with a 1:1 donor: acceptor ratio, but exhibit unique unit cells. The structural variations result in significant differences in the optoelectronic properties of the crystals, as observed in the experiments and electronic‐structure calculations. Raman spectroscopy shows that the α‐polymorph has a degree of charge transfer of about 0.5 e , while the β‐polymorph is nearly neutral. Organic field‐effect transistors fabricated on these crystals reveal that in the same device structure both polymorphs show ambipolar charge transport, but the α‐polymorph exhibits electron‐dominant transport while the β‐polymorph is hole‐dominant. Together, these measurements imply that the transport features result from differing donor–acceptor overlap and consequential varying in frontier molecular orbital mixing, as suggested theoretically for charge‐transfer complexes.