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Energy Level Engineering in Organic Thin Films by Tailored Halogenation
Author(s) -
Ortstein Katrin,
Hutsch Sebastian,
Hinderhofer Alexander,
Vahland Jörn,
Schwarze Martin,
Schellhammer Sebastian,
Hodas Martin,
Geiger Thomas,
Kleemann Hans,
Bettinger Holger F.,
Schreiber Frank,
Ortmann Frank,
Leo Karl
Publication year - 2020
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.202002987
Subject(s) - pentacene , materials science , organic semiconductor , band gap , ionization energy , organic electronics , halogen , semiconductor , chemical physics , electronic band structure , optoelectronics , range (aeronautics) , molecular engineering , ionization , nanotechnology , transistor , ion , condensed matter physics , organic chemistry , thin film transistor , physics , chemistry , voltage , alkyl , layer (electronics) , quantum mechanics , composite material
In modern electronics, it is essential to adapt band structures by adjusting energy levels and band gaps. At first sight, this “band structure engineering” seems impossible in organic semiconductors, which usually exhibit localized electronic states instead of Bloch bands. However, the strong Coulomb interaction in organic semiconductors allows for a continuous shift of the ionization energy (IE) over a wide range by mixing molecules with halogenated derivatives that exhibit different quadrupole moments. Here, this effect of energy level engineering on blends of pentacene and two fluorinated derivatives, in which the position but not the number of fluorine atoms differ, is studied. Structural investigations confirm that pentacene forms intermixed phases in blends with the fluorinated species. The investigation of electronic properties and simulations reveals a much larger shift of the ionization energy (1.5 eV) than in previous studies, allowing to test this model in a range not investigated so far, and emphasizing the role of the position of the halogen atoms. The tuning effect is preserved in electronic devices such as field‐effect transistors and significantly influences device characteristics.