Proceedings of nanoGe Fall Meeting19 (NFM19)
Publication date: 18th July 2019
The efficiency of nanocrystal (NC)-based devices is often limited by the presence of surface states that lead to localized energy levels in the bandgap. Yet, a complete understanding of the nature of these traps remains challenging. Although theoretical modeling has greatly improved our comprehension of the NC surface, several experimental studies suggest the existence of metal-based traps that have not yet been found with theoretical methods. Since there are indications that these metal-based traps form in the presence of excess electrons, we have used density functional theory (DFT) calculations to study the effects of charging II–VI semiconductor NCs with either full or imperfect surface passivation. It is found that charge injection can lead to trap-formation via two pathways: metal atom ejection from perfectly passivated NCs or metal–metal dimer-formation in imperfectly passivated NCs. These results shed light on how L-type amine ligands can passivate NCs, which may also be relevant for charge neutral NCs, where photoexcited electrons could get trapped in metal-based traps. This work has clear implications for n-doping II–VI semiconductor NCs without introducing surface traps due to metal ion reduction.
A.J.H. acknowledges support from the European Research Council Horizon 2020 ERC Grant 678004 (Doping on Demand). I.I. acknowledges The Netherlands Organization of Scientific Research (NWO) for financial support through the Innovational Research Incentive (Vidi) Scheme (Grant 723.013.002). The computational work was carried out on the Dutch national e-infrastructure with the support of the SURF Cooperative.
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