Epitaxial quasi-2D/3D hybrid perovskite heterojunctions for photodetector with enhanced detectivity and stability

Although numerous metal halide perovskite materials have been investigated in the field of optoelectronic, the development of perovskite heterojunctions with exotic structures is still rare. Herein, we report the epitaxial growth of quasi-two-dimensional (Q-2D) perovskites on methylammonium lead iodide (MAPbI₃) single crystals to form perovskite heterojunctions with interfacial bonding. The MAPbI₃ adjacent to epitaxial Q-2D perovskite shows blue shifted photoluminescence with shortened lifetime, which becomes significant with the reduced layer number of the Q-2D perovskites. Our findings suggest the presence of an interfacial strain gradient leading to enhanced photocarrier separation. Accordingly, compared to the MAPbI₃ single crystal detector, the BA₂MAPb₂I₇/MAPbI₃ (BA: n-butylamine) heterojunction-based photodetector demonstrates a bandpass detecting property and exhibits 5 times enhanced external quantum efficiency and 83 times enhanced specific detectivity (D* = 3.26 × 10¹¹ Jones). Remarkably, the unencapsulated BA₂MAPb₂I₇/MAPbI₃ heterojunction is stable in ambient condition for > 300 days. The Q-2D/3D heterojunction shows suppressed ion inter-diffusion due to the presence of Q-2D phase.