Graphene to increase efficiency of perovskite solar cells

Researchers from Italy’s University of Florence have found that graphene oxide could significantly improve the efficiency of perovskite solar cells. The researchers have shown how the introduction of graphene and graphene oxide doped with lithium atoms (GO-Li) into a perovskite-based cell may increase its conversion efficiency, as both the carrier recombination dynamics and the defect density of the perovskite are considerably improved.

The scientists used graphene doped mesoporous TiO2 (G+mTiO2) with the addition of a lithium-neutralized graphene oxide (GO-Li) interlayer as ETL. They found that the carrier collection efficiency is increased by about a factor two with respect to standard mTiO2.

Other research, said the research coordinator, had already used graphene oxide on perovskite cells, but we were the first that adopted optical measurements to investigate the positive effects of this use. The result is important not only for the increased efficiency achieved but also because the same technique can be experienced in other materials. Until now experiments have been carried out on perovskites consisting of an organic-inorganic hybrid compound, the organic part of which unfortunately degrades very rapidly in the presence of moisture. The upcoming future scenario is the use of graphene and graphene oxide on completely inorganic perovskite cells: this will allow new improvements and these new technologies will be closer to commercial production.

Taking advantage of the absorption coefficient dispersion, the sensitized methylammonium lead iodide (MAPI) layer morphology is probed, along the thickness, finding that the MAPI embedded in the ETL composed by G+mTiO2 plus GO-Li brings to a very good crystalline quality of the MAPI layer with a trap density about one order of magnitude lower than that found with the other ETLs, the researchers said.