Improvement in performance of Si-based thin film solar cells with a nanocrystalline SiO2-TiO2 layer

In this paper, titanium dioxide (TiO2) solution with grain sizes of 1-5 nm is prepared by microwave hydrothermal synthesis, and then mixed with silicon dioxide (SiO2) solution to yield different SiO2/TiO2 ratios. The mixed solution is then sol-gel spin-coated on glass as an anti-reflecting and self-cleaning bi-functional layer. The experimental results show that the transmittance is optimized not only by minimizing the reflectance by reflective index matching at the glass/air interface, but also by improving the film/glass interface adhesion. Adding SiO2 into TiO2 in a weight ratio of 5 leads to the highest average transmittance of 93.6% which is 3% higher than that of glass. All of the SiO2-TiO2 films exhibit a remarkable inherent hydrophilicity even when not illuminated by ultra-violet light. Using the optimized SiO2-TiO2 film in a hydrogenated amorphous silicon/microcrystalline silicon tandem, solar cell increases its conversion efficiency by 5.2%. Two months of outdoor testing revealed that cells with the SiO2-TiO2 film avoid 1.7% of the degradation loss that is caused by dust and dirt in the environment. (C) 2014 Elsevier B. V. All rights reserved.