Photoemission Spectroscopy and Atomic Force Microscopy Investigation of Vapor Phase Co-Deposited Silver/Poly(3-hexylthiophene) Composites

TL;DR

This study investigates the microstructure, chemical interactions, and electronic properties of vapor-phase co-deposited silver/P3HT nanocomposites, revealing controllable electronic characteristics and preserved polymer conjugation.

Contribution

It provides new insights into the chemical states, microstructure, and electronic properties of vapor-deposited Ag/P3HT composites, demonstrating tunable barrier heights and preserved polymer order.

Findings

Ag nanoparticles exhibit two chemical binding states with sulfur in P3HT.

Microstructure and surface roughness change with Ag concentration.

Electronic properties such as barrier height can be tuned by adjusting Ag content.

Abstract

Nanocomposite matrices of silver/poly(3-hexylthiophene) (P3HT) were prepared in ultrahigh vacuum through vapor-phase co-deposition. Change in microstructure, chemical nature and electronic properties with increasing filler (Ag) content were investigated using in-situ XPS and UPS, and ambient AFM. At least two chemical binding states occur between Ag nanoparticles and sulfur in P3HT at the immediate contact layer but no evidence of interaction between Ag and carbon (in P3HT) was found. AFM images reveal a change in Ag nanoparticles size with concentration which modifies the microstructure and the average roughness of the surface. Under co-deposition, P3HT largely retains its conjugated structures, which is evidenced by the similar XPS and UPS spectra to those of P3HT films deposited on other substrates. We demonstrate here that the magnitude of the barrier height for hole injection and the position of the highest occupied band edge (HOB) with respect to the Fermi level of Ag can be controlled and changed by adjusting the metal (Ag) content in the composite. Furthermore, UPS reveals distinct features related to the C 2p (Sigma states) in the 5-12 eV regions, indicating the presence of ordered P3HT which is different from solution processed films.