Current solar panel technologies require a sheet of glass to serve as both mechanical support and to protect the cells from the environment. The reflection from the glass sheet can reflect up to 8% of the incident light, reducing the power output of the panel. Antireflective coatings can be used to allow more light to enter the panel to be converted into usable electricity. However, no solid thin film materials exhibit a low enough index of refraction to serve as antireflective coatings for common solar glass. The main goal of this research was to investigate the self-cleaning, antifogging, and antireflective behavior of low index of refraction silica nanoparticle films, with an ultimate goal to develop a method to deposit these films on glass substrates from aqueous solutions.
The optical, wetting, and self-cleaning ability of these films was evaluated at a laboratory scale. It was determined that the film performance could be significantly improved by utilizing a polyvinylpyrrolidone (PVP) adhesion layer during the deposition process. Using this method, the solar weighted transmittance of glass was improved to 97.4%, with peak transmittance of 99.5%, using a double sided coating.
The short-circuit current and conversion efficiency of silicon solar cells was improved by a relative 4.4% over an equivalent cell packaged behind uncoated glass. This represents 50% recovery of the losses associated with packaging. Dual-layer antireflective coatings for both silicon and gallium arsenide solar cells using the silica nanoparticle coating were also created. An average increase of 28% in the short-circuit current and 32% relative improvement in device efficiency was achieved with silicon devices. The average conversion efficiency of the planar silicon cells was increased from 10.6% to 14% by addition of the coating.
In summary, the experimental study of the optical properties and surface morphology of silica nanoparticle films deposited with a PVP adhesion layer demonstrated the potential of these films as optical coatings and functional self-cleaning and antifogging surfaces. The characterization of these silica nanoparticle films provided a fundamental understanding of the relationship between the optical and wetting properties of the nanoparticle coating and the morphology of the film
