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Orientation Control of Linear‐Shaped Molecules in Vacuum‐Deposited Organic Amorphous Films and Its Effect on Carrier Mobilities
Author(s) -
Yokoyama Daisuke,
Setoguchi Yousuke,
Sakaguchi Akio,
Suzuki Michio,
Adachi Chihaya
Publication year - 2010
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.200901684
Subject(s) - materials science , amorphous solid , substrate (aquarium) , molecule , biphenyl , carbazole , vacuum deposition , surface roughness , chemical physics , thin film , crystallography , nanotechnology , composite material , organic chemistry , chemistry , oceanography , geology
The molecular orientation of linear‐shaped molecules in organic amorphous films is demonstrated to be controllable by the substrate temperature. It is also shown that the molecular orientation affects the charge‐transport characteristics of the films. Although linear‐shaped 4,4′‐bis[( N ‐carbazole)styryl]biphenyl molecules deposited on substrates at room temperature are horizontally oriented in amorphous films, their orientation when deposited on heated substrates with smooth surfaces becomes more random as the substrate temperature increases, even at temperatures under the glass transition temperature. Another factor dominating the orientation of the molecules deposited on heated substrates is the surface roughness of the substrate. Lower carrier mobilities are observed in films composed of randomly oriented molecules, demonstrating the significant effect of a horizontal molecular orientation on the charge‐transport characteristics of organic amorphous films.