Visible‐Blind Deep Ultraviolet Photomultiplication Organic Photodetectors with Ultrahigh Gain for UVB and UVC Light Detection

Photomultiplication‐type organic photodetectors (PM‐OPDs) have developed rapidly in UVA, visible and near‐infrared ranges, but they face great challenges in the UVB and UVC ranges, mainly due to the difficulty of simultaneously realizing deep UV light‐transmittance electrode and high gain structure. Here, the copper and silver bilayer composite electrodes are developed to overcome the problem of silver island growth, thus ensuring high deep UV light transmittance and good matching with electrical gain mechanism. The fabricated device shows high external quantum efficiency as high as 195,665% at 255 nm in UVC region. Furthermore, the above electrodes are integrated with low‐cost UV filter glass ZWB1 by simple vacuum evaporation. Finally, low‐cost visible‐blind deep UV PM‐OPDs with a rejection ratio of up to 4788 is achieved through an additional strategy of adjusting the absorption spectrum of the active layer. Benefiting from its fast response speed, the device can be directly applied to faint flame monitoring in real‐time. The ultrahigh gain UVC organic photodetectors are constructed by using high deep‐UV transmittance Cu/Ag bilayer composite electrode and effective photomultiplication structure. Furthermore, a high UV‐vis rejection ratio of up to 4788 is achieved by combining low‐cost UV filter substrates and the spectral tunability of organic materials. Finally, real‐time detection of weak flames is demonstrated.