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

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.