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Highly crystalline perovskite films with large grains and few grain boundaries are conducive for efficient and stable perovskite solar cells. Current methods for preparing perovskite films are mostly based on a fast crystallization process, with rapid nucleation and insufficient growth. In this study, MAPbI 3 perovskite with inhibited nucleation and promoted growth in the TiO 2 /ZrO 2 /carbon triple mesoscopic scaffold was crystallized by modulating the precursor and the crystallization process. N-methylformamide showed high solubility for both methylammonium iodide and PbI 2 and hampered the formation of large colloids in the MAPbI 3 precursor solution. Furthermore, methylammonium chloride was added to reduce large colloids, which are a possible source of nucleation sites. During the crystallization of MAPbI 3 , the solvent was removed at a slow controlled speed, to avoid rapid nucleation and provide sufficient time for crystal growth. As a result, highly oriented MAPbI 3 crystals with suppressed non-radiative recombination and promoted charge transport were obtained in the triple mesoscopic layer with disordered pores. The corresponding hole-conductor-free, printable mesoscopic perovskite solar cells exhibited a highest power conversion efficiency of 18.82%. The device also exhibited promising long-term operational stability of 1000 h under continuous illumination at maximum power point at 55 ± 5 °C and damp-heat stability of 1340 h aging at 85 °C as well as 85% relative humidity., Competing Interests: The authors declare that they have no conflicts of interest in this work., (© 2021 The Authors. Publishing Services by Elsevier B.V. on behalf of KeAi Communications Co. Ltd.)