Chemical encapsulation of perovskite film by tetra-thiol copper(II) porphyrin for stable and clean photovoltaics

Abstract The undersaturated lead or iodide ions can produce defects during the preparation of polycrystalline perovskite films, the defects critically influenced photovoltaic device efficiency and stabilities. The leakage of toxic lead also has certain environmental safety risks. In response to the above problems, we designed a molecular modification strategy for problems. A tetra-thiol copper porphyrin (CuP) molecule was synthesized and used to modify the perovskite film. The Raman spectroscopy tests determined that CuP can be anchored on the surface of perovskite film through the Pb–S bonds between the thiol of CuP and lead on perovskite film surface. The density functional theory (DFT) calculation indicate that CuP can adsorb iodide ion and iodine, then effectively reduced iodide ions and iodine vacancies. In addition, the photoluminescence and space-charge limited current measurements shown that CuP can effectively passivate defects and improve film quality. Finally, the CuP modified PSCs enhancement of the power conversion efficiencies, the best efficiency up to 20.7%. The stabilities of humidity, thermal and photo also improved. Moreover, the surface encapsulation of CuP can also effectively prevent the leakage of lead. This work provides a strategy to fabricate stable and clean PSCs by the in situ chemical coordination on perovskite films.