Photovoltaic and Photomultiplication Dual-Mode Near-Infrared Organic Detectors with Large Dynamic Range for Intensive and Faint Light Sensing.

Conventional detectors usually operate in one detection mode, namely photovoltaic mode, photoconductive mode, or photomultiplication mode, etc., which may have limitations such as insufficient sensitivity and limited dynamic range for applications. In this study, a photovoltaic/photomultiplication dual-mode organic photodetector is developed by integrating two different organic bulk heterojunctions (BHJs), one introduces the photovoltaic effect, and the other triggers photomultiplication charge generation in the stacked device at different voltage polarities. The combination of the two operation modes largely extends the dynamic range of detectors, even superior to that of a commercial silicon detector. The ultra-low noise level of the photovoltaic mode enables it to detect faint light with exceptional sensitivity, while the photomultiplication mode can handle a significantly large saturation photocurrent, allowing for the precise detection of high-intensity signals. A dynamic range of 225 dB is achieved by precisely controlling the operation conditions of the dual-mode detector, which surpasses the dynamic range of 140 dB of a commercial silicon detector. The detector can, as a result, precisely detect light signals (800 nm) in the range of 10-10 W cm. This study demonstrates the versatility of organic semiconductors in designing multi-functional and high-performing photodetectors for practical applications.