A Stendal

Enhancement of the photovoltaic conversion efficiency of copper phthalocyanine thin film devices by incorporation of metal clusters

ITO-copperphthalocyanine-indium sandwich structures have been prepared by thermal evaporation in high vacuum. Different types of metal nanoclusters have been incorporated at the ITO-copperphthalocyanine interface. Significant differences in the photovoltaic conversion efficiency of the sandwich samples have been established as a function of the excitation wavelength. Copper clusters have been found to increase the conversion efficiency by a factor of nearly three for solar illumination. The observed effects are discussed assuming resonant light absorption in the metal clusters as the responsible physical mechanism for enhancement.

The incorporation of metal clusters into thin organic dye layers as a method for producing strongly absorbing composite layers: an oscillator model approach to resonant metal cluster absorption

We present data on the NIR/VIS/UV optical constants of thin composite layers, built up from a copper phthalocyanine matrix with embedded metal clusters. The metal clusters (copper, gold and silver) have diameters on a nanometre scale and act as strong absorption centres. In particular, local plasmon resonances and metal interband transitions could be observed from a fit of the experimentally determined dielectric functions by means of a Lorentzian multi-oscillator model. Average dipole transition matrix elements with respect to a single metal cluster have been estimated from the oscillator parameters.

Gaussian quadrature approach to the calculation of the optical constants in the vicinity of inhomogeneously broadened absorption lines

A fast numerical procedure to calculate the convolution of Gaussian and Lorentzian functions is introduced as well as its application to the approximation of experimental spectra. It is shown that these spectra can be well approximated with the method, especially in the case when the inhomogeneous and homogeneous linewidth contributions as parameters of a Voigt lineshape are of the same order of magnitude. Particularly, the method is applicable to refractive index modelling in the vicinity of inhomogeneously broadened absorption lines.

Tuning of the plasmon absorption frequency of silver and indium nanoclusters via thin amorphous silicon films

Silver and indium nanoclusters have been incorporated into thin sputtered amorphous silicon films. The optical properties of these films have been investigated and compared with the results of spectra simulations. The dependence of the metal cluster plasmon resonance position on the silicon film thickness has been established. Additionally, the inhomogeneous broadening of the plasmon line has been estimated. The data are discussed with respect to the results of transmission electron microscopy.

A statistical approach for interpreting the optical spectra of metal island films: effects of multiple scattering in a statistical assembly of spheres

We calculate the linear optical response of island films, considering, in particular, a statistical character of the geometry of the cluster assembly as well as electromagnetic interaction between the clusters in the film. The work involves Monte Carlo simulations of the island-film growth followed by aggregate calculations of the island-film optical extinction. The results of Monte Carlo simulations are compared with the transmission electron micrographs of silver island films on fused silica. The optical response of the film has been approximated by the extinction of a statistical assembly of spheres, whose sizes and positions have been obtained from the Monte Carlo simulations. The comparison of the calculation with oblique incidence optical transmission spectra allows us to illuminate the role of the various effects contributing to the transmission behaviour of the films.

Enhanced Raman signals in thin solid films formed from fullerene, copperphthalocyanine, or perylene derivates and incorporated metal clusters

Abstract Surface enhanced Raman spectroscopy (SERS) experiments have been carried out in thin organic films with incorporated metal clusters. Copperphthalocyanine, N , N ′-dimethyl-3,4,9,10-perylenedicarboximid (MPP) and fullerene have been used as matrix materials, while the clusters were formed from silver, gold, or copper. In these systems, maximum Raman cross-section enhancement values of the molecular matrix have been found to be around 70. The effects have been attributed to resonant excitation of local plasmon modes in the metal clusters. The Raman spectra are discussed with respect to spectral shape and Raman intensity enhancement in terms of a semiclassical microscopic SERS approach. In particular, the different effects of homogeneous and inhomogeneous plasmon line broadening on the SERS efficiency are extensively discussed.

Linear optical constants of ultrathin copperphthalocyanine films from transmittance and reflectance data: error function minimization when the film thickness is below 20 nm

Thin copperphthalocyanine layers have been deposited on quartz glass substrates and investigated by means of transmission and reflection spectroscopy. The film thickness ranged between 20 nm and the subnanometer region. The determination of the optical constants allowed the estimation of the oscillator strengths for the relevant molecular transitions. A thickness dependence of the Q-band absorption maximum position could be established for layers with a thickness below 5 nm. The contributions of several physical mechanisms to such lineshifts are discussed.