Dipole-Controlled Energy Level Alignment at Dielectric Interfaces in Organic Field-Effect Transistors

In this section the energy level alignment at the semiconductor–dielectric interface in organic field-effect transistors is discussed. We focus at the comparison of pristine oxide structures with advanced organic interlayer structures. The interface is particularly interesting, since the performance of an organic field-effect transistor is significantly influenced by the energy level alignment. The study targets on an understanding of interfacial effects, hence complementary techniques are presented to investigate the interface. Most appropriately a combination of device analysis with a device-related photoemission spectroscopy study provides insight on the energy level alignment. Especially the role of commonly used organic interlayers is discussed, which enhance transistor performances. On organic–organic interfaces dipoles arise, which shift the relative positions of energy levels. Interestingly the magnitude and the direction of the shift is reflected in the device parameter analysis and in the corresponding photoemission spectra explaining the enhanced transistor performance.