Synthesis and Characterization of Phenothiazine-based Small molecule and Polymeric Transparent Organic Hole Transporting Materials for Perovskite Solar Cells

In this work we are presenting the synthesis of novel classes of transparent Hole Transporting Materials (HTMs) based on Low-Cost Phenothiazine (PTZ) for perovskite solar cells applications. Three scaffolds based on PTZ were prepared either by alkylation of the nitrogen atom by nucleophilic substitution in presence of base (scaffold 1) or by Buchwald-Hartwig arylation (scaffold 2). Scaffolds 1 and 2 were brominated using bromine to prepare the intermediates for the coupling reactions, and the brominated scaffold 2 was further oxidized the prepare the scaffold 3 intermediate. The Suzuki coupling was used for the synthesis of small molecule based HTMs, while for the polymeric based HTMs Buchwald amination polymerization was preferred to polymerize the brominated scaffold 1 intermediate with different low-cost anilines. All HTMs were properly characterized with several techniques and were transparent to visible light. The tuning of the phenothiazine core and of their substituents gave access to new HTMs with different properties. Some of them were applied in perovskite solar cells, obtaining interesting results.