Organic photomultiplication photodetectors exhibiting bias-dependent switchable operations between broadband and narrowband responses

Organic photodetectors (OPDs) have attracted significant attention due to their advantages over traditional inorganic semiconductor-based counterparts. Their features of low-cost processing, ease of bandgap tunability, flexible nature, and scalable processing make them great candidates for a wide range of photodetection platforms. Herein, we report photomultiplication-type OPDs prepared with non-fullerene acceptors (NFAs) exhibiting switchable operations between broadband and narrowband responses. The device can switch operations between narrowband and broadband detection modes based on the application of bias of different magnitudes. The use of NFAs extends the spectral response of the OPDs into the near-infrared spectral range. At the low bias of 0.3 V irrespective of polarity, the device shows narrowband responses with an external quantum efficiency (EQE) over 100 %. When the magnitude of bias exceeds 0.5 V, the device switches to broadband detection mode with a spectral range spanning from UV to NIR while maintaining the photomultiplication nature. To the best of our knowledge, high EQE values have never been reported in narrowband photodetectors with dual modes prepared with NFAs. Furthermore, the device shows a fast response up to 10 kHz, making it the fastest reported dual-mode NFA organic photodetector. Such dual-mode detection functionality is achieved without the need for an external optical filter and trans-impedance amplifier. This is beneficial for reducing the complexity of the device and thus greatly simplifies overall instrumentation needs for many applications.