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A Solution‐Processable Liquid‐Crystalline Semiconductor for Low‐Temperature‐Annealed Air‐Stable N‐Channel Field‐Effect Transistors
Author(s) -
Ozdemir Resul,
Choi Donghee,
Ozdemir Mehmet,
Kim Hyekyoung,
Kostakoğlu Sinem Tuncel,
Erkartal Mustafa,
Kim Hyungsug,
Kim Choongik,
Usta Hakan
Publication year - 2017
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.201601430
Subject(s) - materials science , semiconductor , band gap , organic semiconductor , acceptor , homo/lumo , electron mobility , field effect transistor , alkyl , solubility , optoelectronics , analytical chemistry (journal) , transistor , organic chemistry , chemistry , condensed matter physics , molecule , physics , quantum mechanics , voltage
A new solution‐processable and air‐stable liquid‐crystalline n‐channel organic semiconductor (2,2′‐(2,8‐bis(5‐(2‐octyldodecyl)thiophen‐2‐yl)indeno[1,2‐b]fluorene‐6,12‐diylidene)dimalononitrile, α,ω‐2OD‐TIFDMT ) with donor–acceptor–donor (D‐A‐D) π conjugation has been designed, synthesized, and fully characterized. The new semiconductor exhibits a low LUMO energy (−4.19 eV) and a narrow optical bandgap (1.35 eV). The typical pseudo‐focal‐conic fan‐shaped texture of a hexagonal columnar liquid‐crystalline (LC) phase was observed over a wide temperature range. The spin‐coated semiconductor thin films show the formation of large (≈0.5–1 μm) and highly crystalline platelike grains with edge‐on molecular orientations. Low‐temperature‐annealed (50 °C) top‐contact/bottom‐gate OFETs have provided good electron mobility values as high as 0.11 cm 2 (V s) −1 and high I on / I off ratios of 10 7 to 10 8 with excellent ambient stability. This indicates an enhancement of two orders of magnitude (100×) when compared with the β‐substituted parent semiconductor, β‐DD‐TIFDMT (2,2′‐(2,8‐bis(3‐dodecylthiophen‐2‐yl)indeno[1,2‐b]fluorene‐6,12‐diylidene)dimalononitrile). The current rational alkyl‐chain engineering route offers great advantages for D‐A‐D π‐core coplanarity in addition to maintaining good solubility in organic solvents, and leads to favorable optoelectronic/physicochemical characteristics. These remarkable findings demonstrate that α,ω‐2OD‐TIFDMT is a promising semiconductor material for the development of n‐channel OFETs on flexible plastic substrates and LC‐state annealing of the columnar liquid crystals can lower the electron mobility for transistor‐type charge transport.