Fullerene C₆₀-silver nanoparticles hybrid structures: Optical and photoelectric characterization

A detailed optical and photoelectric characterization of pristine fullerene C₆₀ films deposited onto n-silicon substrates (C₆₀/Si), C₆₀ films crosslinked by means of the solvent-free chemical functionalization with 1,8-diaminooctane (C₆₀-DA/Si), and the pristine and crosslinked films decorated with silver nanoparticles (C ₆₀-Ag/Si and C₆₀-DA-Ag/Si), was carried out. The reflectance spectra obtained allowed to calculate the absorption coefficient (α = 47π/λ) spectral dependencies and the spectra of light transmittance in layered barrier structures metal(Au)/fullerene/Si. Photoelectric properties of the films were investigated as well. The experimentally measured values of band gap were in a good agreement with mobility gap values (2.3 ± 0.1 eV). The decoration of fullerene films (both pristine and chemically crosslinked) with silver nanoparticles did not change the photocurrent spectra as compared to those for undecorated fullerene films, but lowered the values of internal quantum efficiency O_int. The photocurrent generated in fullerene/Si heterostructure, showed a maximum value at λ ∼450 nm (Q_{int max} ≈ 0.25 for decorated and undecorated C₆₀-DA/Si films), and it was higher for the samples based on pristine C₆₀ films, in accordance with their higher absorption coefficient. Diminishing of O_int for C₆₀-DA/Si and C ₆₀-DA-Ag/Si films was observed for the spectral range of photocurrent generated in Si layer. The analysis of dark current-voltage characteristics showed that the barrier properties differ insignificantly, though a certain increase of series resistance was observed for the C₆₀-DA/Si samples.