Theoretical modelling of metal-based and metal-free dye sensitizers for efficient dye-sensitized solar cells: A review

Motivated by the great importance of fundamental research in finding new and improved pathways to harvest energy from the sun, the present review provides an account of theoretical modelling sustaining the development of dye-sensitized solar cells (DSSCs). This review starts with a sum up of concepts and factors that guide the efficiency of DSSCs, including the key equations for their evaluation. The operability of the modelling as a screening and predictive tool is demonstrated though analysis of a number of applications, and it is shown how the modelling can lead to prediction of optimal factor values, as well how it is used for interpretation purpose. The analysis is divided up between metal-based and metal-free dye sensitizers, where for the former the Ru-based and Zn-based sensitizers are given an in-depth attention. Various key factors affecting the efficiency of DSSCs are presented, like donor moieties, acceptors and anchoring groups, pi-linkers, use of companion dyes and multistrategies, co-adsorption, aggregation and other mechanisms, where in each case key published theoretical works are highlighted and analyzed. At the end of the review a complementary account is given for machine learning approaches that have increasingly emerged in the last few years as very powerful tools for the prediction of optimal molecules, materials and device constructions in the DSSC field. With this survey, we hope to bring to the fore the notion of theoretical modelling as an indispensable factor in the further development of DSSCs, and other solar cells, for the benefit of climate and society.