Gravity-Guided Growth of Large-Area High-Quality Two-Dimensional Ruddlesden–Popper Perovskite Thin Films for Stable Ultraviolet Photodetectors

Two-dimensional (2D) Ruddlesden–Popper (RP) perovskites are excellent optoelectronic materials due to their natural quantum well structure and enhanced environmental stability. However, the growth of their large-area high-quality thin films is still fundamentally challenging. Herein, a novel gravity-guided growth method is proposed to grow a wafer-scale (∼8 cm²) (PEA)₂PbBr₄ thin films (∼μm) with a centimeter-scale crystal domain on an inclined substrate. A model is established to elucidate the role of gravity in the growth process. It can be concluded that the tip of the precursor solution on an inclined substrate should be preferentially induced to nucleate and crystallize. In addition, the crystallization growth is directionally guided and its velocity increases as the rear contact angle decreases. Experimentally, the controllable inclination angles can optimize the quality and thickness of the films. Moreover, the arrayed photodetectors based on the resulting (PEA)₂PbBr₄ thin films have been demonstrated to have an extremely dark current of 10^–12 A and good environmental stability. After 100 days of storage in the atmosphere for the unencapsulated samples, there is only a small photocurrent degradation of 18%. This work provides a promising solution for scalable fabrication of the large-area high-quality 2D perovskite thin films that can serve as a good candidate for stable photodetectors.