The fill factor (FF) is a fatal parameter to determine the power conversion efficiency (PCE) of perovskite solar cells. Especially, for the large area solar cells and modules, the low FF is the bottleneck towards the high PCE. The FF is highly correlated with the carrier recombination caused by defects at interfaces. Herein, we propose that ultra-thin inorganic alkali metal fluorides interlayer passivate the interface defects by vapor evaporation method at the perovskite/electron transport layer (ETL) interface. We confirmed that the alkali metal fluorides (AF) layer can function as both defect passivation layer and physical barrier layer, showing the significant enhancement of PCE and ambient stability. Eventually, we achieve the highest FF (80.6%) for 1 cm² size and highest FF (73.1%) for 10.8 cm² size perovskite solar cell by potassium fluoride (KF) as passivation layer. This functional interlayer strategy paves the way to resolve the industrial requirements with low cost, high fill factor large area planar perovskite solar cells.

填充因子（FF）是确定钙钛矿太阳能电池功率转换效率（PCE）的致命参数。特别是对于大面积的太阳能电池和组件，低FF是高PCE的瓶颈。FF与界面缺陷引起的载流子重组高度相关。在本文中，我们建议在钙钛矿/电子传输层（ETL）界面处通过气相蒸发法将超薄无机碱金属氟化物夹层钝化界面缺陷。我们确认碱金属氟化物（AF）层既可以用作缺陷钝化层，又可以用作物理阻挡层，显示出PCE和环境稳定性的显着增强。最终，我们达到1 cm ²尺寸的最高FF（80.6％）和10.8 cm的最高FF（73.1％）²尺寸的钙钛矿太阳能电池由氟化钾（KF）用作钝化层。这种功能性夹层策略为低成本，高填充因子大面积平面钙钛矿太阳能电池解决工业需求铺平了道路。