In Situ Growth of Large‐Area and High‐Quality Perovskite Single Crystal Thin Films for Optoelectronic Devices With Superior Stability

ABSTRACT Metal halide perovskite single‐crystal thin films (SCTFs) show great promise for high‐stability optoelectronic applications since their long‐range ordered stacking with large grains, few grain boundaries, and low defect density. However, their growth always requires high temperatures due to the inverse temperature solubility of the precursors, which increases the production costs, and decreases the crystal area and quality. Here, an assisting solvent strategy is developed to achieve in situ growth of large‐area and high‐quality perovskite SCTFs at low temperatures. Tetrahydrofuran serves as the assisting solvent in γ‐butyrolactone to hydrogen bond with the precursor to improve the saturation solubility at room temperature. The resulting SCTFs show a maximum area of over 10 mm ² , a low defect density of 4.42 × 10 ¹² cm ⁻³ , and superior optoelectronic properties. The as‐fabricated self‐powered photodetectors exhibit a high detectivity of 4.01 × 10 ¹² Jones, a large linear dynamic range of 127 dB, and reproducible photocurrent response. Moreover, the devices show long‐term stability in humid conditions, maintaining approximately 90% of the initial photocurrents after being stored for nearly 120 days in 60% relative humidity conditions. Our work not only presents state‐of‐the‐art perovskite photodetectors with superior stability, but also demonstrates the huge potential of perovskite SCTFs in optoelectronic applications.