Effective surface passivation of environment-friendly colloidal quantum dots for highly efficient near-infrared photodetectors

Abstract

Near-infrared (NIR) photodetectors fabricated from colloidal quantum dots (QDs) are promising for next-generation light sensing, thanks to their facile solution-processing, tunable optoelectronic properties and flexible compatibility. However, the majority of current QD-NIR photodetectors are still based on QD materials consisting of extremely toxic heavy metals (e.g. Pb and Hg), which are detrimental to the natural environment and human health, hindering the commercialization prospects. Herein, eco-friendly CuInSnSe (CISnSe) QDs with broadband absorption were engineered via effective ZnSe shell passivation to realize NIR QD-photodetector applications. It is revealed that the ZnSe shell coating on the CISnSe core QDs enables suppressed non-radiative recombination and optimized electronic band structure, thus leading to improved charge carrier population and efficient charge extraction in the corresponding QD-photodetector devices. As a result, the fabricated environment-friendly CISnSe/ZnSe core/shell QD-based photodetectors exhibit responsivities of 0.95 and 0.24 A W⁻¹ as well as detectivities of 1.74 × 10¹⁰ and 3.77 × 10⁹ Jones under NIR 790 and 980 nm illumination (0.5 mW), respectively. Our findings indicate that the rational surface engineering of eco-friendly, narrow-band gap QDs is promising for the fabrication of cost-effective, highly efficient and “green” NIR photodetectors.