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Intrinsic Surface Dipoles Control the Energy Levels of Conjugated Polymers
Author(s) -
Heimel Georg,
Salzmann Ingo,
Duhm Steffen,
Rabe Jürgen P.,
Koch Norbert
Publication year - 2009
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.200901025
Subject(s) - conjugated system , materials science , intramolecular force , polymer , dipole , organic electronics , chemical physics , nanotechnology , organic chemistry , voltage , transistor , composite material , chemistry , physics , quantum mechanics
Conjugated polymers are an important class of materials for organic electronics applications. There, the relative alignment of the electronic energy levels at ubiquitous organic/(in)organic interfaces is known to crucially impact device performance. On the prototypical example of poly(3‐hexylthiophene) and a fluorinated derivative, the energies of the ionization and affinity levels of π ‐conjugated polymers are revealed to critically depend on the orientation of the polymer backbones with respect to such interfaces. Based on extensive first‐principles calculations, an intuitive electrostatic model is developed that quantitatively traces these observations back to intrinsic intramolecular surface dipoles arising from the π ‐electron system and intramolecular polar bonds. The results shed new light on the working principles of organic electronic devices and suggest novel strategies for materials design.