Facile tuning of PbI2 porosity via additive engineering for humid air processable perovskite solar cells

Abstract

Fabrication of perovskite solar cells (PSC) in ambient environment or high relative humidity (RH) condition may assist in reducing the production cost and simplifying the fabrication process. However, processing PSC in high-humidity faces major challenges related to degradation of perovskite material and formation of low-quality film. To this end, we focus on improving the perovskite film quality by introducing 4-tert-butylpyridine (TBP) as additive to manipulate the morphology of PbI2 for fabricating efficient PSC in ambient air with RH30–40%. The amount of TBP is varied between 0 and 15 vol%. It is found that increasing the amount of TBP gradually transforms the compact PbI2 layer to porous structure. This allows methylammonium iodide solution to penetrate deep into the layer even after volume expansion of perovskite crystals. As a result, high-quality perovskite layer with low defect and appropriate amount of PbI2 phase passivation layer is produced. Such feature enhances the light absorption, improves the charge separation and reduces the charge recombination. By increasing the TBP content to 10 vol%, a best efficiency of 15.1% has been acquired and the device also exhibits better ambient stability. The additive engineering approach developed in this work may offer a new insight for the development of efficient and stable PSC under humid atmosphere.