Nanomaterials - 10

Abstract

Solution-processed colloidal III–V semiconductor quantum dot photodiodes (QPDs) have potential applications in short-wavelength infrared (SWIR) imaging due to their tunable spectral response range, possible multiple-exciton generation, operation at 0-V bias voltage and low-cost fabrication and are also expected to replace lead- and mercury-based counterparts that are hampered by reliance on restricted elements (RoHS). Our previous work successfully synthesized InSb quantum dots (QDs) via a solution-based method and utilized these QDs to fabricate SWIR detection diodes. However, similar to other studies, our devices exhibited significant limitations such as excessive dark current and prolonged detection times, attributed to the high surface defect density of the QDs, which diminished their practical application potential.
 In this study, we employed ligand exchange, utilizing sulfur ion oleylamine ligands to reduce the In₂O₃ oxide defects on the surface of the InSb QDs. This modification led to an enhanced photodetection response speed (rise time of 0.1s) and significantly reduced the dark current (as low as nA/cm2). Additionally, the reduced interdot spacing improved the carrier mobility within the QD layer of the device. As a result, the external quantum efficiency (EQE) of the ligand-modified device increased to 18.5%, thereby enhancing the potential of InSb QDs for infrared imaging sensor.