Benzothiazole-based arylamines as hole transporting materials for perovskite solar cells

The performance of perovskite solar cells (PSCs) is partially dependent on the properties of the hole transporting material (HTM) used. Here, we present the synthesis and study of novel benzothiazole-based arylamine HTMs. The compounds are thermally stable, decomposing at temperatures >350 °C, and exist in amorphous states. The ionization potential values of the HTMs are between 5.26-5.62 eV, which are optimal with respect to the valence band energy of perovskite (∼5.7 eV). PSCs employing the best performing HTM resulted in a power conversion efficiency (PCE) of 20.74% with a fill factor (FF) of 77.6%. With this we present donor-π-bridge-acceptor type-strategy as an effective method to increase charge transport properties of benzothiazole-based small molecule HTMs that are obtained in high yield via a simple Knoevenagel condensation reaction resulting in improved performance of the hole transporting layer in PSCs.