Metal-free organic dyes for dye-sensitized solar cells: from structure: property relationships to design rules

Dye-sensitized solar cells (DSSC) have attracted considerable attention in recent years as they offer the possibility of low-cost conversion of photovoltaic energy. This Review focuses on recent advances in molecular design and technological aspects of metal-free organic dyes for applications in dye-sensitized solar cells. Special attention has been paid to the design principles of these dyes and on the effect of various electrolyte systems. Cosensitization, an emerging technique to extend the absorption range, is also discussed as a way to improve the performance of the device. In addition, we report on inverted dyes for photocathodes, which constitutes a relatively new approach for the production of tandem cells. Special consideration has been paid to the correlation between the molecular structure and physical properties to their performance in DSSCs.