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Phenacyl–Thiophene and Quinone Semiconductors Designed for Solution Processability and Air‐Stability in High Mobility n‐Channel Field‐Effect Transistors
Author(s) -
Letizia Joseph A.,
Cronin Scott,
Ortiz Rocio Ponce,
Facchetti Antonio,
Ratner Mark A.,
Marks Tobin J.
Publication year - 2010
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200901513
Subject(s) - phenacyl , thiophene , homo/lumo , materials science , semiconductor , organic semiconductor , electron mobility , organic field effect transistor , field effect transistor , oligomer , chemistry , transistor , polymer chemistry , organic chemistry , molecule , optoelectronics , physics , quantum mechanics , voltage
Electron‐transporting organic semiconductors (n‐channel) for field‐effect transistors (FETs) that are processable in common organic solvents or exhibit air‐stable operation are rare. This investigation addresses both these challenges through rational molecular design and computational predictions of n‐channel FET air‐stability. A series of seven phenacyl–thiophene‐based materials are reported incorporating systematic variations in molecular structure and reduction potential. These compounds are as follows: 5,5′′′‐bis(perfluorophenylcarbonyl)‐2,2′:5′,‐ 2′′:5′′,2′′′‐quaterthiophene ( 1 ), 5,5′′′‐bis(phenacyl)‐2,2′:5′,2′′: 5′′,2′′′‐quaterthiophene ( 2 ), poly[5,5′′′‐(perfluorophenac‐2‐yl)‐4′,4′′‐dioctyl‐2,2′:5′,2′′:5′′,2′′′‐quaterthiophene) ( 3 ), 5,5′′′‐bis(perfluorophenacyl)‐4,4′′′‐dioctyl‐2,2′:5′,2′′:5′′,2′′′‐quaterthiophene ( 4 ), 2,7‐bis((5‐perfluorophenacyl)thiophen‐2‐yl)‐9,10‐phenanthrenequinone ( 5 ), 2,7‐bis[(5‐phenacyl)thiophen‐2‐yl]‐9,10‐phenanthrenequinone ( 6 ), and 2,7‐bis(thiophen‐2‐yl)‐9,10‐phenanthrenequinone, ( 7 ). Optical and electrochemical data reveal that phenacyl functionalization significantly depresses the LUMO energies, and introduction of the quinone fragment results in even greater LUMO stabilization. FET measurements reveal that the films of materials 1 , 3 , 5 , and 6 exhibit n‐channel activity. Notably, oligomer 1 exhibits one of the highest μ e (up to ≈0.3 cm 2 V −1 s −1 ) values reported to date for a solution‐cast organic semiconductor; one of the first n‐channel polymers, 3 , exhibits μ e ≈10 −6 cm 2 V −1 s −1 in spin‐cast films ( μ e =0.02 cm 2 V −1 s −1 for drop‐cast 1 : 3 blend films); and rare air‐stable n‐channel material 5 exhibits n‐channel FET operation with μ e =0.015 cm 2 V −1 s −1 , while maintaining a large I on:off =10 6 for a period greater than one year in air. The crystal structures of 1 and 2 reveal close herringbone interplanar π‐stacking distances (3.50 and 3.43 Å, respectively), whereas the structure of the model quinone compound, 7 , exhibits 3.48 Å cofacial π‐stacking in a slipped, donor‐acceptor motif.