A Minimalist, Flexible, Transparent, and Water‐Degradable Ultraviolet Photodetector for Visible‐Blind Applications

The advancement of flexible and transparent photodetectors represents a technological frontier for wearable electronics and imperceptible monitoring networks. This study presents an ultraviolet (UV) photodetector that harmonizes flexibility, transparency, and water‐degradability within a minimalist bilayer architecture. The device is constructed by seamlessly depositing patterned indium tin oxide (ITO) on cast‐cured polyvinyl alcohol (PVA) films. The ITO serves dual roles as the UV‐sensitive medium and transparent conducting electrodes, while the PVA acts as both a flexible transparent substrates and low‐conductivity transport channel that effectively suppresses dark current. The resulting devices exhibit high optical transparency, retaining >89% transmittance, and a broad spectral response spanning 254–405 nm, covering UVA, UVB and UVC bands. They also demonstrate outstanding mechanical conformability, maintaining stability under extreme deformations (e.g., 60° bending angle, convex bending radii of 0.4 cm) and enduring over 5000 bending cycles with minimal performance degradation. Furthermore, they maintain stable operation under long‐term continuous illumination, high bias voltage (200 V), elevated temperature (150°C), and strong visible‐light interference. Last, the detector enables visible‐blind UV communication via ASCII and Morse encoding schemes. The seamless combination of minimalist design, high transparency, mechanical conformability, and controlled water disposability offers opportunities for imperceptible and sustainable optoelectronic applications.