Theoretical Characterization of GaSb Colloidal Quantum Dots and Their Application to Photocatalytic CO2 Reduction with Water

Near-Infrared Polarimetric Image Sensors Based on Ordered Sulfur-Passivation GaSb Nanowire Arrays

The near-infrared polarimetric image sensor has a wide range of applications in the military and civilian fields, thus developing into a research hotspot in recent years. Because of their distinguishing 1D structure features, the ordered GaSb nanowire (NW) arrays possess potential applications for near-infrared polarization photodetection. In this work, single-crystalline GaSb NWs are synthesized through a sulfur-catalyzed chemical vapor deposition process. A sulfur-passivation thin layer is formed on the NW surface, which prevents the GaSb NW core from being oxidized. The photodetector based on sulfur-passivation GaSb (S-GaSb) NWs has a lower dark current and higher responsivity than that built with pure GaSb NWs. The photodetector exhibits a large responsivity of 9.39 × 10² A/W and an ultrahigh detectivity of 1.10 × 10¹¹ Jones for 1.55 μm incident light. Furthermore, the dichroic ratio of the device is measured to reach 2.65 for polarized 1.55 μm light. Through a COMSOL simulation, it is elucidated that the origin of the polarized photoresponse is the attenuation of a light electric field inside the NW when the angle of incident polarization light rotates. Moreover, a flexible polarimetric image sensor with 5 × 5 pixels is successfully constructed on the ordered S-GaSb NW arrays, and it exhibits a good imaging ability for incident near-infrared polarization light. These good photoresponse properties and polarized imaging abilities can empower ordered S-GaSb NW arrays with technological potentials in next-generation large-scale near-infrared polarimetric imaging sensors.

Tuning the Radiative Lifetime in InP Colloidal Quantum Dots by Controlling the Surface Stoichiometry

InP nanocrystals exhibit a low photoluminescence quantum yield. As in the case of CdS, this is commonly attributed to their poor surface quality and difficult passivation, which give rise to trap states and negatively affect emission. Hence, the strategies adopted to improve their quantum yield have focused on the growth of shells, to improve passivation and get rid of the surface states. Here, we employ state-of-the-art atomistic semiempirical pseudopotential modeling to isolate the effect of surface stoichiometry from features due to the presence of surface trap states and show that, even with an atomistically perfect surface and an ideal passivation, InP nanostructures may still exhibit very long radiative lifetimes (on the order of tens of microseconds), broad and weak emission, and large Stokes' shifts. Furthermore, we find that all these quantities can be varied by orders of magnitude, by simply manipulating the surface composition, and, in particular, the number of surface P atoms. As a consequence it should be possible to substantially increase the quantum yield in these nanostructures by controlling their surface stoichiometry.