The research activity of the R2ES group (Research on Renewable Energy and Sustainability) at the Department of Biotechnology, Chemistry and Pharmacy, University of Siena focuses on the design and characterization of new sensitizers for innovative energy conversion systems from renewable sources and hydrogen production. It also deals with the evaluation of the sustainability of advanced materials and innovative technologies for the conversion of energy from renewable sources and energy storage systems. The R2ES group boasts collaborations with both national and international research laboratories and companies and its research is demonstrated by numerous publications in international high-impact scientific journals.