High‐Detectivity Flexible Near‐Infrared Photodetector Based on Chalcogenide Ag₂Se Nanoparticles

Abstract Novel, low‐voltage, high‐detectivity, solution‐processed, flexible near‐infrared (NIR) photodetectors for optoelectronic applications are realized and their optoelectronic properties are investigated for the first time. This is achieved by synthesizing Ag₂Se nanoparticles (NPs) in aqueous solutions, and depositing highly crystalline Ag₂Se thin films at 150 °C with redistributed Ag₂Se NPs in aqueous inks. The high conductivity and low trap concentration of the 150 °C annealed Ag₂Se films result from the Ag formed inside the films and the improved film quality, respectively. These factors are both critical for the realization of high‐performance flexible photodetectors. The fabricated device exhibits a high detectivity of 7.14 × 10⁹ Jones (above 1 × 10⁹) at room temperature, delivering low power consumption. This detectivity is superior to those of reported low band‐gap semiconductor systems, although the device has undergone 0.38% compressive and tensile strains. Moreover, the performance of the device is better than that of MoS₂‐based phototransistors, black arsenic phosphorus field‐effect transistors, or commercial thermistor bolometers at room temperature (D* ≈ 10⁸ Jones), and is exposed to mid‐infrared light.