An ultra-thin inorganic interlayer strategy for achieving efficient inverted planar perovskite solar cells and modules with high fill factor

Abstract

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 cm 2 size and highest FF (73.1%) for 10.8 cm 2 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. • As for the alkali metal fluorides as passivation layer, the introduce of alkali metal fluorides can effectively reduce the defects at the perovskite surface: the alkali metal fluorides can improve fluorescence intensity and fluorescence lifetime, so that to decrease the surface defect evoked by the surface vacancy. • As for the alkali metal fluorides as physical barrier layer, the introduce of alkali metal fluorides can effectively reduce the carrier recombination at perovskite/transport layer interfaces and improve ambient stability: The inserted inorganic layer can selectively conduct one type of charges while block the other type, which spatially separates photogenerated electrons and holes to reduce their recombination • The inserted inorganic layer increases the contact angle, which obviously improves the device stability.