Intrinsic Surface Dipoles Control the Energy Levels of Conjugated Polymers

Abstract

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.

Operando ESR elucidation of charge accumulation and molecular orientation in ternary polymer solar cell materials using organic electrochemical transistor structures

“…3d), which is consistent with the nding obtained from an earlier study of 2D-GIXD showing that the predominant orientation of PTzBT molecules is face-on orientation 4,22,32 . Consequently, as charge accumulation begins, holes are accumulated primarily in molecules with edge-on orientation for shallow HOMO levels 32 . As V G increases, the charge accumulation amount increases.…”

“…Consequently, the orientation of molecules with charge accumulation is found to be "face-on" (Fig. 3d), which is consistent with the nding obtained from an earlier study of 2D-GIXD showing that the predominant orientation of PTzBT molecules is face-on orientation 4,22,32 . Consequently, as charge accumulation begins, holes are accumulated primarily in molecules with edge-on orientation for shallow HOMO levels 32 .…”

Ordered Growth and Electronic Properties of 1,2:8,9-Dibenzopentacene (trans-DBPen) on Ag(111)

“…The ionization energy decreases from 5.6 to 5.4 eV, which is compatible with our interpretation of tilted trans -DBPen molecules starting to occur somewhere beyond an island height of two layers. Similar cases were already discussed for Pen on Ag(111) and other molecules. ,− …”

From Monolayer to Multilayer N‐Channel Polymeric Field‐Effect Transistors with Precise Conformational Order

“…As observed for oligothiophenes, the valence levels are affected in the same way as the core levels, which directly translates into a variation of the ionization energy. As a reference for P3HT, a decrease of ionization energy by 0.4 eV from the face-on to the edge-on configurations has been calculated, [20] that is in nice agreement with our findings experiencing such effect for the first time on a polymeric system. Once we established control on the P(NDI2OD-T2) film morphology and microstructure, we characterized the field-effect transport properties for edge-on monolayers in a staggered topgate geometry, using PMMA as the gate dielectric (see the inset to Figure 4a).…”