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Title: DOE Earlier Career Award: Modeling of Photoexcited Process at Interfaces of Functionalized Quantum Dots

Abstract

Funded by the DOE grant we achieved the following research results: (i) We combined the time-domain density functional theory (TD-DFT) with the time-dependent density matrix technique (TD-DMT) and developed a new approach to non-adiabatic dynamics (NAMD) allowing us to get insights into various non-radiative relaxation pathways and simulate the time-resolved emission spectra of quantum dots (QDs) with complicated surface chemistry and interfaces. (ii) Using the developed NAMD method, we determined which form – arrays or nanowires – maximizes the absorption and emission of nanostructures and how that efficiency is affected by the interactions between QDs and their structural disorder. In particular, we provided an exploitation of experimentally detected enhancement in blinking ‘on’ time corresponding to the system’s state with the high quantum efficiency in closely packed Si QDs. (iii) Using the NAMD method, we analyzed the fundamental process such as decoherence and Zeno effects in semiconductor nanostructures and established a direct connection between the phonon bottleneck (extremely slow energy dissipation to heat) and Zeno effect. This knowledge will be helpful in controlling dissipation process in QDs via synthetic manipulations of the QD’s shells, dopants, ligands, packing, and interfaces. (iv) Using the NAMD method, we elucidated the role of surface ligandsmore » in photoexcited dynamics of quantum dots (QDs), including slowing of elastic scattering in QDs by ligands providing favorable conditions for multiple excitons generation (MEG), controlling of which holds an important promise for improvement of the solar energy conversion. (v) We have quantified the range of applicability of our DFT-based techniques in predicting both linear and non-linear optical properties of quantum dots (QDs) and confirmed highly efficient two-photon absorption in 1-2 nm CdSe QDs. (vi) We identified mechanisms of the preferential binding of ionic ligands, such as carboxylates, thiolates, and halides, to various QDs. In particular, our calculations explained the mechanisms of formation of two-dimensional nanoplates (NPLs) of PbSe and the role that halide precursors play in controlling the surface direction and thickness of NPLs. This knowledge provides us insights into the nature of interactions between the QD and surface agents governing the efficiency of the optical response in QDs, which is important for their applications in optoelectronic and photovoltaic devices. (vii) We conducted quantum chemistry calculations to model the morphology, the electronic structure, and optical spectra of QDs functionalized by organic dyes and metal-organic complexes, which led us to predictions of the prerequisite conditions that govern the direction and rates of the charge transfer from the QD to the dye. Thus, we obtained important insights into the charge transfer that is a key process in the realization of new nanomaterials for photovoltaic and photocatalytic applications. (viii) Targeting design of metal-organic dyes with enhanced charge transfer and non-linear optical properties, we performed joined computational and experimental studies of optical properties of various Pt(II)-, Ru(II)-, and Ir(III)-complexes and demonstrated the practical realization of DFT-based predictions in rational structure-property design of molecular systems.« less

Authors:
ORCiD logo [1]
  1. North Dakota State Univ., Fargo, ND (United States)
Publication Date:
Research Org.:
North Dakota State Univ., Fargo, ND (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Chemical Sciences, Geosciences & Biosciences Division
Contributing Org.:
North Dakota State University
OSTI Identifier:
1574381
Report Number(s):
DE-SC0008446
DOE Contract Number:  
SC0008446
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
77 NANOSCIENCE AND NANOTECHNOLOGY; Quantum Dots, Charge Transfer, Excited State, first principles, nonadiabatic

Citation Formats

Kilina, Svetlana. DOE Earlier Career Award: Modeling of Photoexcited Process at Interfaces of Functionalized Quantum Dots. United States: N. p., 2019. Web. doi:10.2172/1574381.
Kilina, Svetlana. DOE Earlier Career Award: Modeling of Photoexcited Process at Interfaces of Functionalized Quantum Dots. United States. https://doi.org/10.2172/1574381
Kilina, Svetlana. Mon . "DOE Earlier Career Award: Modeling of Photoexcited Process at Interfaces of Functionalized Quantum Dots". United States. https://doi.org/10.2172/1574381. https://www.osti.gov/servlets/purl/1574381.
@article{osti_1574381,
title = {DOE Earlier Career Award: Modeling of Photoexcited Process at Interfaces of Functionalized Quantum Dots},
author = {Kilina, Svetlana},
abstractNote = {Funded by the DOE grant we achieved the following research results: (i) We combined the time-domain density functional theory (TD-DFT) with the time-dependent density matrix technique (TD-DMT) and developed a new approach to non-adiabatic dynamics (NAMD) allowing us to get insights into various non-radiative relaxation pathways and simulate the time-resolved emission spectra of quantum dots (QDs) with complicated surface chemistry and interfaces. (ii) Using the developed NAMD method, we determined which form – arrays or nanowires – maximizes the absorption and emission of nanostructures and how that efficiency is affected by the interactions between QDs and their structural disorder. In particular, we provided an exploitation of experimentally detected enhancement in blinking ‘on’ time corresponding to the system’s state with the high quantum efficiency in closely packed Si QDs. (iii) Using the NAMD method, we analyzed the fundamental process such as decoherence and Zeno effects in semiconductor nanostructures and established a direct connection between the phonon bottleneck (extremely slow energy dissipation to heat) and Zeno effect. This knowledge will be helpful in controlling dissipation process in QDs via synthetic manipulations of the QD’s shells, dopants, ligands, packing, and interfaces. (iv) Using the NAMD method, we elucidated the role of surface ligands in photoexcited dynamics of quantum dots (QDs), including slowing of elastic scattering in QDs by ligands providing favorable conditions for multiple excitons generation (MEG), controlling of which holds an important promise for improvement of the solar energy conversion. (v) We have quantified the range of applicability of our DFT-based techniques in predicting both linear and non-linear optical properties of quantum dots (QDs) and confirmed highly efficient two-photon absorption in 1-2 nm CdSe QDs. (vi) We identified mechanisms of the preferential binding of ionic ligands, such as carboxylates, thiolates, and halides, to various QDs. In particular, our calculations explained the mechanisms of formation of two-dimensional nanoplates (NPLs) of PbSe and the role that halide precursors play in controlling the surface direction and thickness of NPLs. This knowledge provides us insights into the nature of interactions between the QD and surface agents governing the efficiency of the optical response in QDs, which is important for their applications in optoelectronic and photovoltaic devices. (vii) We conducted quantum chemistry calculations to model the morphology, the electronic structure, and optical spectra of QDs functionalized by organic dyes and metal-organic complexes, which led us to predictions of the prerequisite conditions that govern the direction and rates of the charge transfer from the QD to the dye. Thus, we obtained important insights into the charge transfer that is a key process in the realization of new nanomaterials for photovoltaic and photocatalytic applications. (viii) Targeting design of metal-organic dyes with enhanced charge transfer and non-linear optical properties, we performed joined computational and experimental studies of optical properties of various Pt(II)-, Ru(II)-, and Ir(III)-complexes and demonstrated the practical realization of DFT-based predictions in rational structure-property design of molecular systems.},
doi = {10.2172/1574381},
url = {https://www.osti.gov/biblio/1574381}, journal = {},
number = ,
volume = ,
place = {United States},
year = {2019},
month = {11}
}