Photoaccelerated chemical deposition of PbS thin films: novel applications in decorative coatings and imaging techniques

Abstract

The deposition of PbS thin films from chemical baths is significantly accelerated when exposed to solar radiation or other sources of illumination. The enhanced deposition rate is seen to be a cumulative effect of an increase in the bath temperature due to photothermal conversion as well as to photoactivated deposition at the PbS film. For deposition employing a 1:1 ratio of Pb²⁺:thiourea (TU) in the bath, a film thickness of approximately=0.09 mu m, corresponding to an integrated reflectance in the visible region of approximately=17% and producing a purple appearance in reflected daylight, is obtained in 40 min under solar radiation of 750 W m^-2 as opposed to 80 min inside the laboratory (26 degrees C) and to 55 min when the bath temperature simulates the variation in temperature (i.e. up to 36 degrees C) observed in the bath under solar radiation. The time lag between the three cases can be varied by varying the bath composition. Novel applications of the photoaccelerated deposition process for producing a variably reflective glaze (golden, purple, bluish, etc.) on the glass surface for decorative coatings and to obtain pleasantly reflective latent images, such as a purple image on a golden background, are presented.