DOI: https://doi.org/10.29363/nanoge.emlem.2024.036
Publication date: 13th July 2024
The science and technology of InAs Colloidal Quantum Dots (CQDs) are at the forefront of materials physics, chemistry, and engineering due to their promising applications in near-IR optoelectronics and their non-toxic nature. However, advancing InAs CQD technology is challenging due to complex synthesis processes, poor material quality, surface passivation issues, and surface traps, which result in low quantum yield (QY) and limited ambient stability, thereby restricting device applications.
To address these challenges, we performed advanced theoretical modeling to investigate the impact of surface defects on the electronic and optical properties of InAs CQDs. In particular, by following the Semi-Empirical Pseudopotential Method (SEMP)1,2 we modelled In-rich spherical-shaped isolated QDs with diameters of, 1.8 nm, 2.36 nm, and 2.96 nm, and In-terminated tetrahedral-shaped isolated QDs with a length of 2.55 nm. We predict the presence of unpassivated surface anions to give rise to states in the gap with an L-like character, resulting in an increase in Stokes' shifts and radiative recombination lifetimes in spherical dots, but having the opposite effect (reduced Stokes' shifts and radiative recombination times) in tetrahedra. We attribute these findings to the specific shape of the QDs3.
These findings offer valuable insights into the surface chemistry of InAs CQDs, particularly regarding traps induced by surface defects. This study provides experimentalists with crucial insights related to the characteristics of InAs CQDs, potentially leading to improved material performance and broader application in optoelectronic devices.
This work was financially supported by the Marie-Curie Fellowship Co-Fund, under the "ONISILOS" Program.
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