Plasmonic Enhancement of Colloidal Quantum Dot Infrared Photodetector Photosensitivity

Infrared photodetector based on lead sulfide (PbS) colloidal quantum dot has been shown to be a promising candidate for infrared detectors, due to the low-cost process of fabrication and their extremely high sensitivity. Moreover, these photodetectors have successfully achieved ultrahigh detectivity - exceeding the indium gallium arsenide-based photodetectors - at room temperature. In this paper, PbS colloidal quantum dots have been synthesized through an all-chemical solution process and their X-ray diffraction patterns have been analyzed to verify the quality of the product. Transmission electron micrograph microscopy image confirms the production of 10-nm PbS nanoparticles. The as-synthesized PbS colloidal quantum dots were mixed with MEH-PPV to form a hybrid nanocomposite. PbS/MEH-PPV hybrid nanocomposite was used as an active material to detect infrared photons and convert into electrical current. The photoconductive photodetector was fabricated by drop casting the hybrid nanocomposite on interdigitated electrodes and tested under different conditions. To study the effect of silver nanoparticles on the performance of the device, different concentrations of Ag/PbS composition were used in the structure of the photodetector. The results show that the Ag additive reduces dark current due to band bending and increases photocurrent through plasmonic effect. Thus, a photoconductive photodetector with improved photosensitivity and enhanced performance has been achieved.