Epitaxy growth of MAPbBr_xCl_3-x single-crystalline perovskite films toward spectral selective detection in both broadband and narrowband ranges

Single-crystalline perovskites with low trap density, high mobility, and long diffusion length are ideal for creating high-performance optoelectronic devices. However, growing mixed-halide single-crystalline perovskite films or wafers with arbitrary halide components and controlled thickness is challenging. Here, a liquid-phase epitaxial (LPE) method based on inverse temperature crystallization (ITC) was developed to address this issue, using orientated MAPbCl(3) single crystals as substrates, resulting in a series of single-crystalline MAPbBr(x)Cl(3-x) perovskite films with continuous variable bandgaps from 2.19 eV to 2.91 eV and excellent optical-electrical properties. A series of planar-type photodetectors are designed and fabricated based on the epitaxial single-crystalline MAPbBr(x)Cl(3-x) films, which present a dual-mode detection ability with response in both broadband and narrowband spectra ranges by manipulating the light incident direction from top illumination and bottom illumination, respectively. Through adjusting halide compositions, these photodetectors exhibit a selective optimal response spectrum and excellent optoelectronic detection performance, demonstrating the potential for multi-functional spectral detection with epitaxial perovskite devices.