Efficient and stable perovskite solar cells based on perfluorinated polymers

In this work, two novel polymeric semiconductors (D2 and D3), with perfluorinated side chains in their backbone, were developed. Moreover, a novel small molecule (D1), with a similar structure to polymers D2 and D3, was also designed for comparison purposes. Compounds D1-D3 were successfully synthesized, completely characterized and used as additives in perovskite solar cells (PSCs). The novel materials contain 26 fluorine atoms per unit, which is the largest amount of fluorine atoms reported for additives in PSCs. In this regard, D1-D3 were incorporated into the perovskite layer as additives and their effect on the film formation, stability and performance of PSCs was studied. As a result, D1-D3-based devices showed very good performances comparable to devices fabricated without additives and an increased stability. Thus, D1- A nd D2-fabricated devices retained 94 and 85% of their initial power, respectively, after 80 min under a bias, while the reference devices broke down completely. These results illustrate the extraordinary protective action of the perfluorinated polymers against humidity and oxygen, even at a low concentration of 2 mg ml^-1 used in our experiments.