Inhibiting the Growth of 1D Intermediates in Quasi‐2D Ruddlesden−Popper Perovskites

Abstract Quasi‐2D perovskite solar cells have recently emerged as a highly prospective and inexpensive solution for sustainable energy due to their intrinsic optoelectronic properties and stability. The qualities of these promising quasi‐2D perovskite cells are generally affected by different intermediates derived from the precursor solution during film fabrication processing. However, efficient solutions to inhibit intermediates remain insufficient to date. Here, an effective strategy is prsented to inhibit the growth of 1D solvate intermediate during the fabricating process of quasi‐2D perovskite films by introducing a guanidinium thiocyanate (GUASCN) inhibitor. Theoretical calculations reveal that the SCN − anions spontaneously replace the iodide ions in the inorganic framework [PbI 6 ] 3− and induce the decomposition of the solvate intermediate. The resulted perovskite solar cells exhibit a significant improvement in power conversion efficiency (PCE), benefiting from the reduced trap‐state density and enhanced carrier mobilities. The unencapsulated devices retain 91% and 95% of the original PCEs under 45 ± 10% humidity in air or under continuous light irradiation at 100 mW cm −2 and 45 °C in a nitrogen atmosphere for 1000 h. Particularly, devices without electron‐transporting layers maintain 85% of the peak PCE under maximum power point tracking at 45 °C for 1000 h.