The effect of porous lead iodide precursor film on perovskite film formation and its photovoltaic property after an effective pretreatment

• Crystalline porous PbI2 precursor films prepared by solvent SND pretreatment.
• The time of SND pretreatment is critical to PbI2 precursor film.
• 10 min pretreatment PbI2 precursor film makes the perovskite device of 8.6%.

An effective solvent sealed natural drying (SND) pretreatment was introduced for forming a satisfactory crystalline porous iodide (PbI2) precursor film, which could help to generate excellent CH3NH3PbI3 perovskite films for high performance of planar heterojunction perovskite solar cells. And the influence of SND pretreated time on the device performance was investigated in detail. We found that the PbI2 precursor film after 10 min pretreatment could make the perovskite device achieve the optimal power conversion efficiency (PCE) of 8.6%, significantly increased up to 95.5% and 28.4% compared to without pretreatment or traditional treatment. The results show that the time of SND pretreatment is critical to forming large grain size and good crystallinity for PbI2 precursor film, which would markedly improve the efficiency of planar heterojunction perovskite solar cells.