Electrostatic Shielding to Stabilize Buried Interface Toward High‐Performance Inorganic Perovskite Solar Cells

Halide migration limits the stability of inorganic perovskite solar cells. It is demonstrated that the perovskite thin film undergoes a non-photovoltaic phase transition at a high temperature of 100 °C with a hole transport layer Poly(3-hexylthiophene-2,5-diyl) (P3HT), due to the iodine diffusion to P3HT through electrostatic interaction. To address this issue, a charge depolarization strategy is implemented by incorporating Chevrel phase Mo₆S₈ nanosheets into P3HT. The covalent coupling between Mo₆S₈ and the P3HT backbone redistributes interfacial charges, effectively suppressing the positive potential sites (C δ⁺) in P3HT and reducing its electrostatic attraction to iodine ions. The charge transfer through the S─Mo bond promotes the P3HT oxidized states generation and rearranges the energy alignment, which thereby contributes to a highly efficient charge collection in solar cell devices. The device structure used is FTO/TiO₂/CsPbI_2.95Br_0.05/P3HT/Ag. When the Mo₆S₈-incorporated, the PCE of perovskite solar cells improves from 18.43 to 20.46%. The inorganic devices demonstrate high stability, retaining 93% of their initial efficiency after 5280 h in ambient air (t = 25 °C, R.H. = 25%) and 95% of their initial efficiency after 989 h at 85 °C in ambient air.