In situ formation of an inorganic lead oxysalt surface passivation layer for highly efficient and stable CsPbI₃ perovskite solar cells

Herein, the surface of all-inorganic CsPbI3 perovskites is converted into water-insoluble lead(ii) chromate via the in situ reaction of Pb(ii) cations with chromate, considerably improving the efficiency and stability of all-inorganic perovskite solar cell (PSC) devices. A lead chromate passivation layer formed on the surface of the CsPbI3 perovskite films. These thin coatings of lead chromate salt effectively reduce the defect density on the perovskite surface by passivating uncoordinated surface lead centers to form strong Pb-O ionic bonds. The hydrophobicity of lead chromate enhances the water resistance of the perovskite film. Because of their inorganic nature, the lead chromate-passivated PSC devices show enhanced heat stability compared to the phenethyl ammonium iodide-passivated PSC devices. The formation of a lead oxysalt layer increases the carrier recombination life and improves the efficiency of the solar cell from 17.96% to 19.09%. Encapsulated devices can maintain 96.03% of their initial efficiency after storage at 25% +/- 5% relative humidity in air for 500 h and 95.62% of their initial efficiency after annealing at 80 C-degrees in N-2 for 500 h.