Formamidine and cesium-based quasi-two-dimensional perovskites as photovoltaic absorbers.

Formamidine (FA) and cesium (Cs) cations were introduced into quasi-two-dimensional (2D) perovskites as B site cations. The unique crystalline growth of the resulting (n-C6H13NH3)2FAPb2I7, which promotes charge transport in photovoltaic solar cells, was confirmed, as was the stability of this material. The photovoltaic properties of (n-C6H13NH3)2FAPb2I7 were found to be superior to those of other homologous quasi-2D perovskite compounds.