Abstract:

The efficiency of metal halide perovskite solar cells has skyrocketed, however defects created by aging precursor solutions and during crystallization pose a significant barrier to reproducibility and efficiency of solar cells. Herein, we report an additive method using Fluoro-N,N,N',N'-tetramethylformamidinium hexafluorophosphate (F-(CH₃)₄-N₂H₄PF₆, abbreviated as TFFH) to stabilize precursor solution and improve crysallization dynamics simutaneously for high-performance FAPbI₃ (FA=formamidinium)-based perovskite indoor photovoltaics. The F-(CH₃)₄-N₂H₄ cations stabilize precursor solution by inhibiting oxidation of I⁻ and reducing newly generated I⁰ to I⁻ simultaneously. The PF₆⁻ anions interact strongly with the Pb-I framework to passivate undercoordinated Pb²⁺. Time-resolved optical diagnostics show a prolonged perovskite crystallization dynamics during which in situ defect passivation is achieved in the precesence of strong FA⁺···TFFH···Pb-I interaction. Simultaneous regulation of precursor solution and crystallizaiton dynamics guarantee larger perovskite grain sizes, better crystal orientation, and less defects of perovskite films as well as more efficient charge extraction in complete solar cells. The optimized solar cells achieve improved reproducibility, better stability and reach effciency of 42.43% at illumination of 1002 lux, which is the highest efficiency among all indoor photovoltaics. It is anticipated that the concurrent stabilization of solutions and regulation of crystallization dynamics will emerge as a prevalent approach for enhancing the reproducibility and efficiency of perovskite.

http://onlinelibrary.wiley.com/doi/full/10.1002/adma.202304809