Graded refraction index antireflection coatings based on silicon and titanium oxides

Thin films with a graded refraction index constituted from silicon and titanium oxides were deposited by plasma enhanced chemical vapor deposition using electron cyclotron resonance. A plasma of oxygen reacted with two precursors: the tetraethoxysilane (TEOS) and the titanium isopropoxide (TIPT). The automatic regulation of the precursor flows makes it possible to modify the chemical composition, and consequently the optical index, through the deposited films. To control the thickness, the refraction index and the growth kinetics, in situ spectroscopic ellipsometer was adapted to the reactor. The analysis of ex situ ellipsometric spectra measured at the end of each deposition allow to determine a refraction index profile and optical properties of the inhomogeneous deposited films. Measurements of reflectivity carried out in the ultraviolet-visible-near infrared range show that these films could be used as antireflective coatings for silicon solar cells: 3.7 % weighted average reflectivity between 300 and 1100 nm and 48 % improvement of the photo-generated current were obtained

Reflection loss minimization for a ZnO/CdS/CuInSe₂ photovoltaic cell

A photovoltaic cell, based on copper and indium selenide (CuInSe₂) thin layers, with a good efficiency can be achieved by simple, easy to implement and low cost techniques. The high refractive index materials used as absorbers in photovoltaic cells cause high reflection losses (about 30%). Thin CdS and ZnO films that are, respectively, the buffer layer and the window of the cell have lower indices and are naturally suited to antireflective applications. Also, a suitable choice of the film thickness leads to minimization of reflection losses, resulting in a significant improvement of the photovoltaic efficiency. The aim of this work is to provide easy solutions that reduce reflection losses to less than 4% while respecting technological constraints

L'etude de l'influence des oxydes sur les proprietes electriques des composants electroniques en phosphure d'indium

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

An original way to obtain porous Zn(1–x)MgxO thin films by spray pyrolysis technique

Zn(1–x)MgxO thin films with various concentrations of magnesium were deposited using the spray pyrolysis method. The transmittance spectra recorded for all films exhibit maxima exceeding 90%. The band gap energy of the films with wurtzite structure increases from 3.22 up to 3.60 eV by incorporating Mg into ZnO. However, when the atomic ratio of Mg exceeded 0.4, a second crystalline phase (assigned to cubic MgO) became discernable in XRD patterns, a compressive strain was observed in the wurtzite lattice, and crystallite sizes decreased significantly. In accordance with these observations, finer grains with a pronounced columnar growth were observed in 3D AFM representations and the surface roughness decreases significantly. Finally, selective etching in water yields to porous films with a great surface-to-volume ratio, a lower refractive index and a better light transmission. These porous films with tunable band gap seem to be excellent candidates to various interesting applications