Electron–phonon and electron–electron interactions in organic field effect transistors

Abstract

Recent experiments have demonstrated that the performances of organic FETs strongly depend on the dielectric properties of the gate insulator. In particular, it has been shown that the temperature dependence of the mobility evolves from a metallic-like to an insulating behavior upon increasing the dielectric constant of the gate material. This phenomenon can be explained in terms of the formation of small polarons, due to the polar interaction of the charge carriers with the phonons at the organic/dielectric interface. Building on this model, the possible consequences of the Coulomb repulsion between the carriers at high concentrations are analyzed.

Hopping and trapping mechanisms in organic field-effect transistors

“…Similar results were used by Fratini et al to justify the existence of small polarons in the channel of single-crystal rubrene transistors 14,17,31,32 that exhibited room-temperature mobilities as high as 20 cm 2 / V s. Their model 32 was used to interpret the dependence of the mobility on both the temperature and the dielectric constant of the gate. 14…”

“…17,31,32 We now examine both models in a manner that includes the effects of polarization discussed in the previous sections.…”

“…This situation is well described by a Fröhlich surface polaron Hamiltonian. Depending on the distance of the carrier to the gate interface and the nature of the dielectric, the coupling is either strong 15,17 or weak to moderate. 16 In the strong-coupling limit, the charge tends to form a small polaron, 17 whereas the carrier is less localized in the moderate coupling regime.…”

“…Depending on the distance of the carrier to the gate interface and the nature of the dielectric, the coupling is either strong 15,17 or weak to moderate. 16 In the strong-coupling limit, the charge tends to form a small polaron, 17 whereas the carrier is less localized in the moderate coupling regime. 16 In this paper, we discuss both trap-limited and smallpolaron hopping transport mechanisms in the channel of an organic transistor close to gate interface.…”

Two-dimensional quasi-freestanding molecular crystals for high-performance organic field-effect transistors

“…4c, Supplementary Fig. 33a) due to additional sources of scattering such as electron-electron interactions 35 . The drastic improvement of mobility indicated that the density of charge traps and grain boundaries was significantly reduced 8 .…”