Energy, from the research of the PoliMi more efficient solar cells

Perovskite-based solar cells more efficient thanks to supramolecular chemistry. This is the new horizon outlined by a study by the Milan Polytechnic. Supramolecular chemistry – which deals with multimolecular systems – and in particular halogen bonding, i.e. the intermolecular interaction involving halogen atoms (I, Br and Cl) present in organic molecules – can help improve the performance of solar cells based on perovskites, allowing to reach high efficiencies and high stability. And this is the conclusion of the researchers of the Politecnico di Milano who have published in the prestigious Angewandte Chemie International Edition. The researchers explain that hybrid organic-inorganic perovskites – ionic compounds made up of small organic cations and metal halides – have been known since the 19th century, but have only recently been used in optoelectronics for the construction of lasers, diodes, photodetectors and cells. solar. In particular, the first perovskite-based photovoltaic cell was produced in 2009 and since then there has been an intense research activity that has made it possible to achieve an efficiency of more than 25%, even surpassing the silicon that currently dominates the photovoltaic market. The low cost and excellent performance of perovskites make them very attractive for photovoltaic applications, but, the PoliMi scholars warn, there are still a series of problems that prevent these materials from entering the market. First of all, their low stability to air and humidity. Furthermore, the presence of defects, or imperfections of the crystal lattice, can generate “trap states” that interfere with the movement of the charge carriers (electrons and holes) generated by the light inside the material, trapping them and thus causing energy losses. electric. Generally these trap states are unbound halide ions that can move under the effect of an electric field and recombine with holes. The study conducted at the Politecnico highlighted how the use of additives capable of forming a halogen bond with the halide ions present in perovskites, brings considerable advantages for the development of solar cells with better crystallinity and greater stability.