Chain-Assisted Charge Transport in Semicrystalline Conjugated Polymers

Abstract

Charge-carrier transport in a paradigmatic semicrystalline polymer semiconductor (P3HT) is important for both fundamental understanding and applications. In samples with enhanced structural disorder due to ad-hoc point defects, the mobility displays rich behavior as a function of electric field (F) and temperature (T ). At low T , the mobility increases with the applied field but upon further increasing T, the field-dependence becomes shallower. Eventually, at the highest T considered, the slope changes sign and the mobility then decreases with the field. This phenomenon can be interpreted with our model as a result of the competition between intra-chain conductive-like transport (which slows down on increasing F) and interchain activated transport (which is faster at higher F). The former is controlling at high T where inter-chain hops are strictly limited to nearest-neighbour monomers on adjacent chains. At low-T, instead, inter-chain hops to distant sites are allowed and control the positive correlation of the mobility with the field.

Charge delocalization characteristics of regioregular high mobility polymers

“…Consistent with previous studies, 17–19 the differences in mobility likely lie in the way the polymers pack together and the electronic coupling between the chains in the bulk. This coupling can only be assessed with precise geometrical information on the relative distances, orientation and translations between chains; information that is not available at this point in time.…”

“…16 In the case of hopping transport in disordered systems, the interchain ordering, or morphology, is a deterministic factor that limits transport. 17–19 Electron–phonon coupling determining the reorganization energies for single electron-transfer events may be a lesser factor, however, its role nevertheless needs to be clarified in relation to the regiochemistry at a single polymer chain level. Moreover, reorganization energies along with electronic couplings provide the necessary microscopic input into theoretical global dispersive transport simulations provided that the morphology of the materials is well understood.…”

Generalized Kinetic Monte Carlo Framework for Organic Electronics

“…Therefore, charge transport along polymer chains, called intrachain transport, is faster than charge transport between two separate polymer chains, which we refer to as inter-chain transport [51][52][53]. Vanlaeke et al showed that crystallization of P3HT increases the mobility [54].…”

“…While for some devices such as OLEDs, a low mobility is critical to optimize the performance, OSCs and OTFTs demand a high mobility. In semiconducting polymers, charge carrier mobility strongly depends on the morphology [54,55], but its interplay is not well understood [52,96]. Investigating the impact of different transport mechanisms, such as intrachain hopping, on carrier mobility can help the development of organic materials and improve device performance.…”

Harnessing Entropy in Single-Molecule Force Spectroscopy with Semiconducting Polymers

“…Besides the elucidation of mechanical response and polymer dynamics at the molecular scale, another application could be the identification of the pathways taken by charges in semiconducting polymer materials for solar cells, where the charge mobility is linked in a non-trivial way to the macromolecule conformation. 11 However, challenges both in the implementation of this method and in the method itself remain; for example, chemical inhomogeneity in the polymeric force sensors leads to signal broadening. Improvement of the synthetic protocols would enable a more fine-tuned detection of forces in which the artificial signal due to chemical heterogeneity is suppressed.…”