Cetrimonium bromide and potassium thiocyanate assisted post-vapor treatment approach to enhance power conversion efficiency and stability of FAPbI(3) perovskite solar cells

Formamidinium lead iodide (FAPbI(3)) is the most promising perovskite material for producing efficient perovskite solar cells (PSCs). Here, we develop a facile method to obtain an α-phase FAPbI(3) layer with passivated grain boundaries and weakened non-radiative recombination. For this aim, during the FAPbI(3) fabrication process, cetrimonium bromide + 5% potassium thiocyanate (CTABr + 5% KSCN) vapor post-treatment is introduced to remove non-perovskite phases in the FAPbI(3) layer. Incorporation of CTA(+) along with SCN(−) ions induces FAPbI(3) crystallization and stitch grain boundaries, resulting in PSCs with lower defect losses. The vapor-assisted deposition increases the carriers' lifetime in the FAPbI(3) and facilitates charge transport at the interfacial perovskite/hole transport layer via a band alignment phenomenon. The treated α-FAPbI(3) layers bring an excellent PCE of 22.34%, higher than the 19.48% PCE recorded for control PSCs. Besides, the well-oriented FAPbI(3) and its higher hydrophobic behavior originating from CTABr materials lead to improved stability in the treated PSCs.