Solution-Processed Perovskite Photoabsorbers with Mixed Cations for Improved Stability in Solar Cells

Perovskite solar cells (PSCs) have been the centre of attention for third-generation photovoltaics ever since power conversion efficiencies (PCEs) of similar to 9.7% were reported in 2012. Since then, intense activity in perovskite research has resulted in a certified PCE of 25.5% in 2020 for single-junction PSCs. This feat can be partly ascribed to the development of various thin film deposition techniques to grow perovskite films, particularly using solution processing techniques. Following the pioneering work resulting from methylammonium lead triiodide (MAPbI(3)) PSCs, formamidinium (FA(+)) cation has been investigated by various research groups as another promising candidate for the 'A'-site cation in the photoabsorber layer, largely due to its improved environmental stability and extended light absorption approaching the near infra-red (NIR) region of the light spectrum compared to methylammonium (MA(+)) cation. In the present study, we have studied the solution-processed mixed MA(+)/FA(+) cation-based perovskite (i.e. MA(1-x)FA(x)PbI(3)) and compared the properties of MA(1-x)FA(x)PbI(3) and MAPbI(3) perovskite films.