Brilliant white polystyrene microsphere film as a diffuse back reflector for solar cells

• Brilliant white films of randomly distributed PS microspheres were fabricated.
• The 20-μm-thick films exhibited high reflectivity and excellent diffuse properties.
• The films were applied as back reflectors for silicon thin film solar cells.
• The films greatly enhanced the short circuit current and efficiency.

Inspired by the microstructures in brilliant white beetle scales, we prepared films composed of randomly distributed dielectric polystyrene (PS) microspheres by a coagulation method. It is found that the about 20-μm-thick microsphere films appear brilliant white, with up to 98% reflectivity in the visible and near-infrared (IR) range and excellent scattering properties close to the Lambertian reflector. The microsphere films were applied as back reflectors for silicon thin-film solar cells, and enhanced the short circuit current and conversion efficiency by 31.2% and 36.7% on average, respectively. The fabrication of the films is low-cost, simple and mild, which is applicable for mass production.