Improvement of Plasmonic CuS Nanocrystals’ Optoelectronic Properties via Cation Exchange for Infrared Detection Enhancement

Colloidal quantum dot (CQD) active thin films benefitting from plasmonic light trapping have emerged as an ideal platform to boost the performance of optoelectronic devices. Copper chalcogenides exhibit infrared absorption in concomitance with tunable localized surface plasmon resonances (LSPRs) within the near to mid infrared range. Regardless of the facile adjustment of the plasmonic oscillation and strong absorption in the infrared range, the application is limited due to very short-living photo-carriers followed by carrier recombination (∼100 ps). Herein, CuS nanocrystals (NCs) are developed as an infrared photoactive material to be functionalized via Pb2+ cation substitution. A short period of cation exchange causes a large reduction in photoluminescence, reaching efficient photo-response in near infrared as a consequence of charge separation. Estimated detectivity and responsivity as high as 2.16 × 1011 Jones and 870 mA W–1 at 750 nm illumination, respectively, were achieved. Increased reaction time and Pb2+ contents result in a growing trend in photoluminescence intensity, consistent with trap passivation: detectivity = 2.15 × 1011 Jones and responsivity = 730 mA W–1 at 950 nm illumination and 1.94 × 1011 Jones and 659 mA W–1 at 840 nm. Manipulation of optical and electrical properties of Cu2–xS NCs with precise cation substitution may open up possibilities for the application of plasmonic semiconductor NCs in optoelectronic devices.