Organic semiconductors: A theoretical characterization of the basic parameters governing charge transport

TLDR

Organic semiconductors based on π‑conjugated oligomers and polymers are key components of plastic optoelectronic devices, and their performance is largely governed by charge‑transport efficiency, especially the magnitude of electronic transfer integrals between adjacent chains. This study uses quantum‑chemical calculations to investigate how the nature and relative positioning of interacting units affect the transfer integrals between adjacent chains. The calculations were performed on model systems comprising oligothienylenes, hexabenzocoronene, oligoacenes, and perylene. Results show that transfer integrals are highly sensitive to molecular packing, and certain arrangements can produce electron mobilities exceeding hole mobilities, as observed for perylene.

Abstract

Organic semiconductors based on pi-conjugated oligomers and polymers constitute the active elements in new generations of plastic (opto)electronic devices. The performance of these devices depends largely on the efficiency of the charge-transport processes; at the microscopic level, one of the major parameters governing the transport properties is the amplitude of the electronic transfer integrals between adjacent oligomer or polymer chains. Here, quantum-chemical calculations are performed on model systems to address the way transfer integrals between adjacent chains are affected by the nature and relative positions of the interacting units. Compounds under investigation include oligothienylenes, hexabenzocoronene, oligoacenes, and perylene. It is shown that the amplitude of the transfer integrals is extremely sensitive to the molecular packing. Interestingly, in contrast to conventional wisdom, specific arrangements can lead to electron mobilities that are larger than hole mobilities, which is, for instance, the case of perylene.