Highly Stable and Efficient Mesoporous and Hollow Silica Antireflection Coatings for Perovskite Solar Cells

Fresnel reflection at the air–substrate interface of a solar cell inevitably occurs causing an important optical loss in photovoltaic conversion efficiency. Transparent materials with a low reflective index are prerequisites for efficient antireflection coating (ARC) to virtually eliminate Fresnel loss but are not readily available. Herein, we developed two methods to reduce the refractive index of the silica by incorporating hollow or mesoporous nanostructures into the film. The application of structured silica ARC in perovskite solar cells can effectively reduce specular light reflection in the broad wavelength range, leading to a significant efficiency enhancement from 19% to above 20% and a clear reduction of the dependence of power conversion on the incidence angle of light. Furthermore, the high hydrophobicity and chemical inertness of the silica render the substrate a self-protection property against dust and water uptake and excellent long-term stability under outdoor operational conditions. Therefore, the solution-processed silica ARCs provide an efficient and cost-effective way to maximize light harvesting in perovskite solar cells, possessing prominent application potential to reduce the levelized cost of energy for photovoltaic grid parity.