PbS solar control coatings: safety, cost and optimisation

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Abstract
Assessments of safety and cost and the optimisation of chemically deposited PbS thin films for solar control applications are presented. The maximum integrated infrared reflectance, 44%, is obtained at a PbS thin film thickness of approximately=95 nm. The corresponding value of the solar control parameters (AM2 case) are: integrated infrared transmittance, 45%; integrated visible transmittance, 17% (yellowish appearance); integrated visible reflectance, 21% (purple appearance); and integrated solar absorptance, 36%. The total solar radiation and heat transfer into the building through a glazing with such a PbS coating is less than 44%, as compared with the approximately=84% of 3 mm thick clear glass, giving a shading coefficient of approximately=50%. A film thickness of 95 nm is obtainable with a deposition time of 50 min from a bath (at 24 degrees C) containing Pb2+ ions and thiourea in the 1:3 molar ratio. However, molar ratios up to 1:5 may be employed, thereby enabling the reduction of deposition time to 35 min. Analyses of the safety and the cost of these coatings have shown excellent promise for their application as medium-efficiency low-cost solar control coatings appropriate for small-scale industrial and 'do-it-yourself' production of the coatings.