Flexible p-i-n perovskite solar cell with optimized performance by KBF4 additive.

Flexible perovskite solar cells (F-PSCs) prevail in the clean energy field for their light weight, easy fabrication and installation, but the power conversion efficiency of F-PSCs needs further improvement. In this work, we numerically simulate and experimentally demonstrate the effect of the perovskite trap defects density on the power conversion efficiency. The pseudo-halide KBF4 is employed as the additive to passivate the trap defects in the perovskite films. The high electrophilicity of BF4 - group ensures its entering into perovskite lattice, optimizing crystallinity and improving the qualities of perovskite films, K+ ions can effectively passivate grain boundaries and inhibit halide anion migrations. After KBF4 passivation, trap defect density of the perovskite film was decreased from 8.0 × 1015cm-3 to 3.9 × 1015cm-3, and also the carrier lifetime increased from 108.52 ns to 234.72 ns. Consequently, the power conversion efficiency (PCE) of the F-PSCs devices increased from 13.99% to 16.04%.