How structural and vibrational features affect optoelectronic properties of non-stoichiometric quantum dots: computational insights. Issue 15 (4th April 2023)

• Record Type: Journal Article
• Authors: Bhati, Manav; Ivanov, Sergei A.; Senftle, Thomas P.; Tretiak, Sergei; Ghosh, Dibyajyoti
• Is Part Of: Nanoscale. Volume 15:Issue 15(2023)
• Page Start: 7176
• Page End: 7185
• Publication Date: 2023-04-04
• Subjects: Nanoscience -- Periodicals; Nanotechnology -- Periodicals; 620.505
• DOI: 10.1039/d2nr06785d
• Languages: English
• ISSNs: 2040-3364

Abstract

Abstract : Ab initio molecular dynamics calculations on non-stoichiometric QDs reveal that dynamic Se atoms influences optical modes and HOMO fluctuations to the greatest extent, thereby weaking photoluminescence in Se-rich QDs compared to Cd-rich QDs. Abstract : While stoichiometric quantum dots (QDs) have been well studied, a significant knowledge gap remains in the atomistic understanding of the non-stoichiometric ones, which are predominantly present during the experimental synthesis. Here, we investigate the effect of thermal fluctuations on structural and vibrational properties of non-stoichiometric cadmium selenide (CdSe) nanoclusters: anion-rich (Se-rich) and cation-rich (Cd-rich) using ab initio molecular dynamics (AIMD) simulations. While the excess atoms on the surface fluctuate more for a given QD type, the optical phonon modes are mostly composed of Se atoms dynamics, irrespective of the composition. Moreover, Se-rich QDs have higher bandgap fluctuations compared to Cd-rich QDs, suggesting poor optical properties of Se-rich QDs. Additionally, non-adiabatic molecular dynamics (NAMD) suggests faster non-radiative recombination for Cd-rich QDs. Altogether, this work provides insights into the dynamic electronic properties of non-stoichiometric QDs and proposes a rationale for the observed optical stability and superiority of cation-rich candidates for light emission applications.