Highly photosensitive near infrared photodetector based on polypyrrole nanoparticle incorporated with CdS quantum dots

Abstract

Photoconductive films in near-infrared (NIR) were fabricated based on low bandgap (1.36 eV) polypyrrole (PPy) and polypyrrole doped with cadmium sulfide quantum dots (PPy/CdS QDs) as organic photodetectors (PDs). The performance of the PDs was evaluated when the PPy incorporated with different amounts of CdS QDs during the chemical polymerization. The represented PDs showed good photosensitivity at 850 nm with different light intensities (0.4–173 mW) and their responses were linear dependency with increasing the light intensities. The best photosensitivity behavior was obtained when the PPy doped with 22 ppm of CdS QDs and the photoresponsivity was enhanced almost six times compared to the undoped PPy PD. The PPy/CdS QDs (22 ppm) PD exhibits a high overall performance with a photoresponsivity of 3.8 mA/W, on/off ratio of 120, EQE of 560% and specific detectivity of up to 2.1 × 1016 Jones. This improvement was mainly attributed to efficiency and increased mobility of generated charge carriers in the photoconductive film based on PPy/CdS QDs (22 ppm) in NIR. It was verified by the UV–vis absorption when the absorption peak in the NIR region of the PPy/CdS QDs (22 ppm) has a shift of 20 nm toward the NIR region in compare to PPy. So, the PPy/CdS QDs PD with high sensitivity and low-cost fabrication made it practically useful in NIR sensors.