Flexible p-i-n perovskite solar cell with optimized performance by KBF 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 KBF is employed as the additive to passivate the trap defects in the perovskite films. The high electrophilicity of BF 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 KBF passivation, trap defect density of the perovskite film was decreased from 8.0 × 10cm to 3.9 × 10cm, 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%.