ABSTRACT Restriction of Hazardous Substances (RoHS) compliant InAs colloidal quantum dots (CQDs) are a class of promising nanomaterials for near infrared optoelectronics. However, the presence of long‐chain organic ligands severely limits their electrical conductivity, and the influence of temperature on ligand dynamics remains poorly understood. Here, we investigate spin‐coated InAs/ZnSe CQD thin films on SiO 2 /Si substrates subjected to annealing up to 300°C in air. Steady‐state and time‐resolved photoluminescence measurements reveal that emission properties are partially preserved up to 250°C. Raman spectroscopy and X‐ray diffraction (XRD) analyses confirm the retention of crystal structure throughout the annealing process. Notably, Kelvin probe force microscopy (KPFM) indicates a substantial change in contact potential difference (CDP) at 250°C, coinciding with a pronounced increase in electrical conductivity from current density‐voltage measurements. This enhancement is attributed to the partial desorption of oleylamine (OLA) ligands, as supported by Raman, Fourier transform infrared spectroscopy (FTIR), Thermogravimetric analysis (TGA) and X‐ray Photoelectron Spectroscopy (XPS) analyses, which lowers interparticle barriers and facilitates charge transport while maintaining film morphology. These findings highlight the critical interplay between ligand chemistry, structural stability, and charge transport, demonstrating that thermal annealing provides an effective pathway to enhance electrical performance while preserving optical quality in InAs/ZnSe CQD films.
Thakur et al. (Tue,) studied this question.