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Ambipolar Transport in the Smectic E Phase of 2‐Propyl‐5′′‐Hexynylterthiophene Derivative over a Wide Temperature Range
Author(s) -
Funahashi Masahiro,
Zhang Fapei,
Tamaoki Nobuyuki,
Hanna Junichi
Publication year - 2008
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.200800206
Subject(s) - ambipolar diffusion , electron , phase (matter) , atmospheric temperature range , electron mobility , homo/lumo , terthiophene , chemistry , materials science , molecule , condensed matter physics , physics , organic chemistry , thermodynamics , quantum mechanics
5‐Hexyl‐5′′‐hexynyl‐2,2′:5′,2′′‐terthiophene exhibits the smectic E phase below 200 °C and does not crystallize when it is cooled to −100 °C. Between 200 and −100 °C, non‐dispersive transport is observed for holes and electrons with time‐of‐flight spectroscopy. Over the entire temperature range, the electron mobility is approximately twice as high as that of the hole. The hole and electron transport characteristics in the smectic phase below 0 °C are explained by the Gaussian disorder model, which was proposed for amorphous organic semiconductors. The disorder parameters, σ and Σ , are almost the same for holes and electrons. However, the pre‐exponential parameter μ 0 for the electron is twice as large as that for the hole, which can be attributed to the difference in the extension of the LUMO of the molecules. The energetic disorder σ is primarily determined by the disorder in the orientation of the permanent dipoles of liquid crystal molecules.