Influence of self-assembled monolayers on electronic properties of poly(3-hexylthiophene) at the polymer/substrate interface*

The impact of self-assembled monolayers (SAMs) on electronic properties of poly(3-hexylthiopene) (P3HT) thin films, of different morphologies, at P3HT/substrate interfaces is reported. The SAMs, trichloro(1H,1H,2H,2H-perfluorooctyl)silane (FTS) and octadecyltrichlorosilane (OTS), modified the surface energy and work function (WF) of indium tin oxide substrates, which influenced charge transfer and band bending behavior of P3HT films at the polymer/substrate interface. This band bending behavior could not be explained solely in terms of substrate WF modification. Investigations of P3HT films fabricated via matrix-assisted pulsed laser evaporation (MAPLE) and spin-casting revealed that the degrees of band bending and breadths of densities of states were associated with changes to electronic structure, strongly affected by the morphological structures of films. The morphological structures of films were influenced by film fabrication method and surface energies of the substrates. The implications of our findings are that the electronic properties of the system are influenced by the WFs and surface energies of SAM-modified substrates and the morphologies of thin P3HT films.<sup>1

1</sup>Wenderott, J. K.; Green, P.F. ACS Appl. Mater. Interfaces, 10 (25), 2018.