A comparison of model calculations and experimental results on photoluminescence energy and open circuit voltage of µc-Si:H solar cells

A simple model is proposed to calculate photoluminescence (PL) spectra and open circuit voltages (V-oc) in thin film p-i-n microcrystalline silicon (mu c-Si:H) solar cells with different structural compositions, as a function of temperature. By using a new technique, namely voltage-modulated PL on solar cells, experimental data are obtained that can be directly compared with the model. The model is based on the distributions of electrons and holes in quasi-equilibrium conditions. Recombination between the two distributions determines the PL band (energy and width of the spectrum). A symmetrical density of states distribution (DOS) described by a superposition of a DOS like that in c-Si and band tail states for the conduction and valence bands is assumed, The best agreement between the model calculations and experimental results for two solar cells with different structural properties is obtained by using an E-o approximate to 0.031 eV for the slope of both exponential band tail states

ZnO:H thin films for room temperature selective NH3 sensors

International audienceZnO thin films were deposited by magnetron sputtering in Ar and Ar+H2 atmospheres. The influence of the substrate temperature, Ts, on their optical, structural and electrical properties was investigated. The optical band gap, Eopt, of the films, from transmission and reflection spectra, ranged from 3.27 to 3.31 eV, and decreased with increasing Ts. The Urbach band tail width was also calculated - its value decreased with increasing substrate temperature. XRD analyses showed an improvement of the structural properties with increasing Ts. A discussion of the influence of Ts and hydrogen on the properties is presented. The change of the sensitivity in the presence of NH3 vapour at room temperature is also presented

Dependence of the photoluminescence intensity of Tb(3+) ions in thin films on the deposition conditions

This paper presents results on the deposition and characterization of thin silica and alumina films containing TP(3+) ions, prepared by magnetron co-sputtering The films are intended for applications as spectral converters of the solar spectrum in thin film silicon solar cells The dependence of the photoluminescence intensity in the films on the deposition parameters and position on the substrate is studied, in order to assess the suitability of this method of preparation for the stated purpose, and to optimize the deposition conditions At a distance of 7 5 cm between the target and the growing film, strong dependence of the photoluminescence (PL) intensity and film thickness on the substrate radial position is observed The increased PL intensity over the erosion zone is explained by bombardment of the growing film by particles from the plasma, which causes a better dispersion of Tb ions and less clustering However, greater distances between the target and substrates should be used for achieving a homogeneous PL intensity and thicknes