Preparation and optical-electronic properties of thin films comprising P3HT and few-layer graphene nanosheets

Abstract

The present work investigates the production of thin films from nanocomposites obtained by solution mixing a synthesized P3HT with different proportions of few-layered graphene (FLG) in chloroform and its influence on crystallography and light absorption in the visible region. Commercial FLG produced through exfoliation in the liquid phase assisted by a non-anionic surfactant was employed, being a material not yet tested for the production of nanocomposites, let alone to be applied in photovoltaic cells. The deposition of thin films was evaluated at low (1000 rpm) and high (2500 rpm) rotation speeds in a dynamic and static deposition process. In addition, the annealing heat treatment in the optimized thin films was evaluated. The results showed that the P3HT was synthesized with suitable molar mass, regioregularity, and thermal resistance as characterized by the analyses of gel permeation chromatography (GPC), 1H-nuclear magnetic resonance (1H NMR), and thermogravimetric analysis (TGA). The thin films produced showed that the FLG enlarged and strengthened the P3HT absorption, increasing the absorption region by up to 34 % in addition to improving the resolution of the absorption peaks favoring the π-π* transition, which is important for the photovoltaic effect. By the X-ray diffraction analysis, it can be suggested that incorporating the FLG improves the charge mobility as there was an increase in the crystallite size without changing the interplanar distance. Based on these results, it can be suggested that P3HT/FLG nanocomposites are promising for application in both the active and hole transport layers of solar cells.