On‐Chip Mercury‐Free Deep‐UV Light‐Emitting Sources with Ultrahigh Germicidal Efficiency

Abstract In the current COVID‐19 scenario, there is an urgent need for developing efficient and mercury‐free deep‐ultraviolet (deep‐UV) light sources for disinfection applications. AlGaN‐based light‐emitting diodes (LEDs) may be considered as an alternative, but due to their inherent low efficiencies in the deep‐UV spectral region, significant developments are required to address efficiency issues. Here, a mercury‐free chip‐size deep‐UV light source is shown which is enabled by high‐vacuum chip‐scale cavity sealing overcoming the limitations of both mercury lamps and deep‐UV LEDs. These deep‐UV chips are cathodoluminescence based, in which a cavity is created with high vacuum integrity for efficient field‐emission. These chips demonstrate optical output power ≥20 mW (efficiency ≈4%) and, owing to the spectral overlap of phosphor cathodoluminescence spectra and germicidal effectiveness curve, resulted in log 6 (99.9999%) germicidal efficiency. Additionally, these chips offer high reliability, “instant” ON/OFF capability, high operational lifetimes, and low‐temperature dependence with complete design freedom.