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

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 Cs₂AgBiBr₆/Cs₃Bi₂Br₉-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.