Synthesis of High-Quality Multilayer Hexagonal Boron Nitride Films on Au Foils for Ultrahigh Rejection Ratio Solar-Blind Photodetection

Solar-blind photodetectors have widespread applications due to the unique merit of a "black background" on the earth. However, most solar-blind photodetectors reported previously exhibited quite low rejection ratios (R_200nm/R_280nm < 10³) and were interfered with by light longer than 280 nm. Herein, by an ambient pressure chemical vapor deposition (CVD) method, large-area, clean, and uniform two-dimensional (2D) multilayer h-BN films with different thicknesses have been successfully synthesized on Au foils. The synthesized multilayer h-BN film is transparent to light longer than 280 nm, showing excellent optical and optoelectronic properties to weak solar-blind light (μW/cm²). This sensitive solar-blind h-BN photodetector exhibits ultrahigh rejection ratios (R_220nm/R_280nm > 10³ and R_220nm/R_290nm > 10⁴), a low dark current (10² fA), and a large detectivity (3.9 × 10¹⁰ Jones). It is noteworthy that the rejection ratio (R_220nm/R_290nm) here is superior to most of those previously reported based on traditional semiconductors. This large-scale, clean, and uniform multilayer h-BN film will contribute to the progress of next-generation optoelectronic devices.