Improved efficiency of silicon polycrystalline commercial photovoltaic cells coated with a co-doped Er3+/Yb3+ silica matrix

Electrical energy produced by photovoltaic cells is extremely interesting because it originates from a clean and renewable source. However, cell efficiency is low due to factors such as temperature, solar spectrum radiation intensity, and incomplete use of all solar radiation wavelengths reaching the Earth (e.g., infrared radiation). Solar radiation reaching the Earth's surface has ultraviolet, visible, and infrared components, which has motivated us to coat commercial polycrystalline silicon cells purchased from Panda Energy Solar Importation LTDA-ME with a silica matrix obtained by the sol-gel process and co-doped with Er3+/Yb3+ lanthanide ions, to promote upconversion. The solar cells prepared herein were coated with thin films via the dip-coating technique and were dried at two different temperatures. The resulting coated photovoltaic cells were characterized by photoluminescence and electrical measurements; voltage, current, and electrical power were considered. Upon excitation at 980 nm, typical Er3+ emission bands emerged in the green (546 nm) and red (650 nm) regions. The emission band at 546 nm was more intense, indicating that the mechanism involved excitation by two photons, and that intensity depended on laser power. Electrical measurements showed that cell efficiency increased when the cell was covered with the thin film.