Bilayer-Assisted Substrate Engineering for Fully Vacuum-Deposited CsPbI₂Br Perovskite Photodetectors

The advancement of all-inorganic metal halide perovskites for visible light detection has been constrained by challenges in scalable, continuous fabrication that ensure both high-quality film formation and robust device stability. Here, we report one of the few all-inorganic perovskite photodetectors (PDs) fabricated entirely through a fully vacuum-based, continuous deposition process, without any solution processing, using a bilayer-engineered substrate to promote uniform crystallization and optimal interface formation. The CsPbI₂Br PD achieves a dark current density of 9.2 × 10^-10 A cm^-2, a specific detectivity (D*) of 2.0 × 10¹³ Jones, and a fast response time of ∼2 μs, along with a linear dynamic range of 109 dB and a cutoff frequency exceeding 300 kHz, underscoring its utility in high-speed optical communication and real-time audio transmission. Long-term operational stability is also demonstrated, with the device retaining 70% of its initial photocurrent after 30 days under continuous AM 1.5G illumination. Importantly, we integrated the PD into a functional Li-Fi system, successfully validating its data transmission capability. Notably, the proposed fabrication route is fully compatible with existing OLED manufacturing processes, providing a clear pathway for future integration of perovskite-based photodetectors into mature optoelectronic production lines. This work establishes a rare, continuous, and fully vacuum-deposited fabrication strategy for all-inorganic perovskite PDs, advancing their readiness for scalable, high-speed optoelectronic applications.