The output decline of solar photovoltaic modules as their temperature increase during operation is a major concern for developers and users. This paper investigates the utilization of a passive evaporative cooling technique to control the temperature rise of PV modules that occurs due to the absorption of solar irradiance. The method involves incorporating a layer of synthetic clay to the back of the module and allowing a thin film of water to evaporate, and thus reducing the module temperature. The results have proven the technical feasibility of the proposed approach by exhibiting a maximum increase of 19.4% to the output voltage and 19.1% to the output power. The incorporation of clay is very effective, cheap, silent and environmentally friendly.