Transient conductive-radiative numerical analysis of multilayer thin filmsheated by different laser pulses

A thermal and optical one-dimensional numerical analysis of semi-transparen t single and multilayer thin films on a transparent thermically semi-infini te glass substrate, irradiated by a laser source, is presented, in classica l conductive Fourier hypothesis. The absorption is evaluated by means of th e classical optical matrix method. Both in thermal and optical models the e ffects of temperature on the properties are taken into account. A pulsed la ser source impinges on the glass side of the structure. Four different typi cal pulse shapes are compared at the same energy amount: a rectangular on-o ff shape, a symmetric triangular shape, a Gaussian shape, an asymmetric tri angular Weibull profile. Numerical calculations are performed, with referen ce to a Nd-YAG pulsed laser and to the three structures by means of which a n amorphous silicon photovoltaic cell is progressively manufactured: a sing le transparent conductive oxide SnO2 (TCO) layer, a double layer of amorpho us silicon (a-Si) and TCO, an Al/a-Si/TCO multilayer thin film. In each cas e the single or composite thin films are on a glass substrate. Results are reported in terms of depth and time profiles of radiative coefficients and temperature. (C) 2001 Editions scientifiques et medicales Elsevier SAS.