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

Abstract

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.