Strategies to improve the performance of metal-free dye-sensitized solar cells

In recent years dye-sensitized solar cells (DSSCs) have attracted more and more attention due to many advantages such as high molar absorption coefficient, facile molecular tailoring and simple fabrication process as compared to conventional silicon devices. High-energy conversion efficiency is one of the most important factors for the large-scale commercialization. However, the maximum reported DSSCs efficiency of 12.3% is still short of the performance of silicon devices (above 25%) and other commercialized technologies. Even lower efficiency for metal-free organic dyes as sensitizers in DSSCs have been reported. Therefore much work is required to reach optimal efficiency. Improving performance of metal-free DSSCs is a great challenge to the academic research community and for industrial applications scientists. The purpose of this review is to highlight the recent progress in improving the performance of metal-free DSSCs based on the chemical design of the sensitizer and interface molecular engineering principles.