Eco‐Friendly In‐Plane Epitaxial Growth of 2D/3D Perovskite Hetero‐Crystal for Efficient X‐ray Detection

ABSTRACT In‐plane lateral growth of hetero‐crystals enables combining the advantages of two dimentional (2D) and three dimentional (3D) semiconductors and exhibits exceptional conductivity to avoid an inter‐layer carrier transport process. Lead‐free perovskites have attracted wide interest due to their robust crystal stability, which provides a low ion migration rate even under high voltage bias and long‐term operation. However, epitaxial growth of in‐plane heterostructures of 2D/3D lead‐free perovskites is still challenging due to the mismatch in their crystallographic constants. Here, we developed an intercalation modulation method via inorganic ion ligand kinetics, enabling in‐plane lateral epitaxial growth of the 2D/3D Cs ₂ AgBiBr ₆ /Cs ₃ Bi ₂ Br ₉ ‐Ag (CABB/CBB‐Ag) halide perovskite hetero‐crystals. In this process, Ag ⁺ intercalation modulates the in‐plane interlayer lattice spacing in 2D CBB to enhance lattice compatibility with 3D CABB, enabling periodic connectivity patterns at the CABB/CBB‐Ag hetero‐crystals for near‐atomically sharp boundaries. Additionally, we demonstrated an excellent sensitivity of 1980 µC Gy _air ⁻¹ cm ⁻² at 700 V for Bi‐based halide perovskite X‐ray detectors due to the built‐in electrical field and the complementary optoelectronic characteristics of the hetero‐crystals. The high‐voltage bias endurance of the detectors is contributed to by the large bonding energy of Bi‐based halide perovskites (∼3.94 eV) compared with lead/tin‐based ones (∼2.57 eV). Our study offers insights into the epitaxial growth of mixed‐dimensional semiconductor hetero‐crystals, and promises high‐performance X‐ray detectors for X‐ray imaging flat panels.