Enhanced thermodynamic stability and carrier lifetime in BF4-doped wide-band-gap perovskite solar cells

Recent experiments show that doping a small amount of fluorinated pseudohalides $\left({\mathrm{BF}}_4\right)$ into ${\mathrm{CH}}_3{\mathrm{NH}}_3{\mathrm{PbI}}_3$ $\left({\mathrm{MAPbI}}_3\right)$ can enhance the performance of wide-band-gap (WBG) perovskite solar cells. Using time-domain density functional theory and ab initio nonadiabatic molecular dynamics we demonstrate that ${\mathrm{BF}}_4$-doped WBG perovskites not only maintain the high defect tolerance but also exhibit greatly improved thermodynamic stability due to enhanced dissociation energy and reduced thermal atomic fluctuation. The strengthened hydrogen bond network introduces increased lattice rigidity, confined inner space, and the reorientated dipole direction of methylammonium molecules, which synergistically suppress the ion migration in ${\mathrm{BF}}_4$-doped ${\mathrm{MAPbI}}_3$ perovskite. Notably, the charge carrier lifetime experiences an order-of-magnitude improvement after ${\mathrm{BF}}_4$ doping, which is mainly attributed to the weakened nonadiabatic coupling. This work provides valuable insights into the effect of fluorinated pseudohalides doped in perovskite materials and suggests a promising approach to enhancing the stability and efficiency of WBG perovskite solar cells.