Investigation of Damp Heat aging on soda-lime glass for photovoltaic applications

International audienceDamp heat test was performed on commercial soda-lime glass to characterize functional properties of glass in photovoltaic applications and to define aging mechanisms. In addition to the measurements of optical properties, FTIR, SEM-EDX and XPS analyses were carried out. The damp heat exposed samples presented an increased transmittance in UV, visible and near-IR ranges. The results were explained by hydration of glass network with heat. Molecular water adsorption involves a leaching process of network modifier cations and especially sodium ions. Hydrolysis also occurs in silica network with free molecular water reaction. This phenomenon enhances concentration of hydroxyl groups in glass highlighted by FTIR measurements and promotes formation of silanol groups. The tin side dependence on sodium leaching which acts as a passivating barrier for ionic transport is emphasized which would be worth taking into consideration for photovoltaic module design

Etude du vieillissement des verres : corrélation entre émissivité apparente (IR) et transmittance (visible)

International audienceLe verre joue un rôle majeur comme protection supérieure, substrat et piégeage de la lumière dans la plupart des systèmes PV. Cependant, des travaux ont montré qu'au cours de sa durée de vie, un panneau solaire photovoltaïque perd entre 10 et 15% de son rendement, essentiellement à cause de pertes optiques. Nous avons testé une méthode de contrôle non destructif et non intrusif permettant de diagnostiquer l'état de vieillissement du verre sodocalcique, à l'aide d'une caméra LWIR. La caractérisation du verre sodocalcique exposé à la chaleur humide durant 1000 h a mis en évidence la pertinence de l'utilisation de l'émissivité apparente comme indicateur de vieillissement. Deux cinétiques de dégradation sont alors apparues lors du vieillissement accéléré. Nous avons également montré la correspondance entre vieillissement naturel et vieillissement accéléré sous UV. Les modifications provoquées par le vieillissement sous UV sont qualitativement identiques pour les spectres de transmittance dans la gamme [300-2300 nm], au contraire du vieillissement sous chaleur humide

Improvement of temperature homogeneity of a silicon wafer heated in a rapid thermal system (RTP: Rapid Thermal Process) by a filtering window

Rapid thermal processes are used in various key stages in the microelectronics industry. In this study, the heat transfer in a rapid thermal system is modelled with the finite volume method. The influence of the radiative properties of the quartz window on the thermal profile of the silicon wafer is first investigated. The obtained temperatures are interpreted by analyzing the radiative properties according to wavelength and temperature. The wafer temperature profile for a non-optimized heating in steady-state is explained by a four-phase scheme where the radiative heat fluxes are depicted. From this scheme, a filter on the underside of the quartz window is envisaged to achieve temperature uniformity for the wafer. Two configurations are tested, one where the filter covers the entire lower surface of the quartz window and another where it is placed in a ring close to the reactor wall to confine the infrared radiations with wavelengths beyond 2.6 μm in order to raise the temperature at the edge of the wafer. Simulations demonstrate that the latter modification enables a more significant improvement of the wafer temperature homogeneity with less than 1% dispersion. The implementation of the filtering window is also discussed