Intermediate-Controlled\nSynthesis of Quasi-2D (PEA)<sub>2</sub>MA<sub>4</sub>Pb<sub>5</sub>I<sub>16</sub> in the 20–30%\nRelative Humidity Glovebox Environment for Fabricating Perovskite\nSolar Cells w

Herein, quasi-two-dimensional\n(Q-2D) (PEA)<sub>2</sub>MA<sub>4</sub>Pb<sub>5</sub>I<sub>16</sub> (prepared by a two-step process) and\nhole transport layer of a solar cell were fabricated in a high relative\nhumidity (25 ± 5%) environment. The PSC behavior of most Q-2D\nperovskites is worse than that of three-dimensional perovskites owing\nto the horizontal alignment of the innate characteristic organic plates\non the substrate. Using hybrid immersion solvents (HISs), we have\nimproved vertical alignment in an appropriate ratio to enhance the\nefficiency of charge transfer and the high coverage of the first priming\nlayer (first step). The grazing incidence X-ray diffraction pattern\nof the optimized structures revealed a preferential orientation for\nthe vertical alignment of (111), which improved the charge transfer\nin PSCs and micrometer-level grain size growth. The second step was\nprocessed in a high-humidity environment (50 ± 5%) (methylammonium\niodide solution embedded), and Q-2D (PEA)<sub>2</sub>MA<sub>4</sub>Pb<sub>5</sub>I<sub>16</sub> demonstrated distinct grain boundaries.\nThe power conversion efficiency (PCE, 13.09%) of the champion device\nof the first priming layer prepared using the HIS system increased\nby >55% compared to the single-immersion solvent (8.3%). The PCE\nof\nthe ion-modified ETL PSCs was 16.02% (CsF-3) and 14.58% (CsCl-3) and\ndemonstrated 22 and 11% improvement, respectively. The ion-modified\nelectron transport layer (ETL) was deposited in the air, which reduced\nthe power consumption of preparing perovskite solar cells (PSCs).\nFinally, all Q-2D PSCs were stored in the air, and three PSCs (DMF/DMSO,\nCsF-3, and CsCl-3) using HIS exhibited long-term stability for 1 month\nmaintaining 80–88% of PCE, demonstrating the importance of\nthe HIS system to improve the first step of growth orientation, which\nenhances the stability and photovoltaic properties of PSCs.