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Setting carriers free : healing faulty interfaces promotes delocalization and transport in nanocrystal solids

(2019) ACS NANO. 13(11). p.12774-12786
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Abstract
Superlattices of epitaxially connected nanocrystals (NCs) are model systems to study electronic and optical properties of NC arrays. Using elemental analysis and structural analysis by in situ X-ray fluorescence and grazing-incidence small-angle scattering, respectively, we show that epitaxial superlattices of PbSe NCs keep their structural integrity up to temperatures of 300 degrees C; an ideal starting point to assess the effect of gentle thermal annealing on the superlattice properties. We find that annealing such superlattices between 75 and 150 degrees C induces a marked red shift of the NC band-edge transition. In fact, the post-annealing band-edge reflects theoretical predictions on the impact of charge carrier delocalization in these epitaxial superlattices. In addition, we observe a pronounced enhancement of the charge carrier mobility and a reduction of the hopping activation energy after mild annealing. While the superstructure remains intact at these temperatures, structural defect studies through X-ray diffraction indicate that annealing markedly decreases the density of point defects and edge dislocations. This indicates that the connections between NCs in as-synthesized superlattices still form a major source of grain boundaries and defects, which prevent carrier delocalization over multiple NCs and hamper NC-to-NC transport. Overcoming the limitations imposed by interfacial defects is therefore an essential next step in the development of high-quality optoelectronic devices based on NC solids.
Keywords
nanomaterials, self-assembly, nanocrystal solids, charge transport, grain boundary, nanocrystal-nanocrystal interface, defects, QUANTUM, ASSEMBLIES, PBS

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MLA
Walravens, Willem, et al. “Setting Carriers Free : Healing Faulty Interfaces Promotes Delocalization and Transport in Nanocrystal Solids.” ACS NANO, vol. 13, no. 11, 2019, pp. 12774–86.
APA
Walravens, W., Solano, E., Geenen, F., Dendooven, J., Gorobtsov, O., Tadjine, A., … Hens, Z. (2019). Setting carriers free : healing faulty interfaces promotes delocalization and transport in nanocrystal solids. ACS NANO, 13(11), 12774–12786.
Chicago author-date
Walravens, Willem, Eduardo Solano, Filip Geenen, Jolien Dendooven, Oleg Gorobtsov, Athmane Tadjine, Nayyera Mahmoud, et al. 2019. “Setting Carriers Free : Healing Faulty Interfaces Promotes Delocalization and Transport in Nanocrystal Solids.” ACS NANO 13 (11): 12774–86.
Chicago author-date (all authors)
Walravens, Willem, Eduardo Solano, Filip Geenen, Jolien Dendooven, Oleg Gorobtsov, Athmane Tadjine, Nayyera Mahmoud, Patrick Peiwen Ding, Jacob P. C. Ruff, Andrej Singer, Günther Roelkens, Christophe Delerue, Christophe Detavernier, and Zeger Hens. 2019. “Setting Carriers Free : Healing Faulty Interfaces Promotes Delocalization and Transport in Nanocrystal Solids.” ACS NANO 13 (11): 12774–12786.
Vancouver
1.
Walravens W, Solano E, Geenen F, Dendooven J, Gorobtsov O, Tadjine A, et al. Setting carriers free : healing faulty interfaces promotes delocalization and transport in nanocrystal solids. ACS NANO. 2019;13(11):12774–86.
IEEE
[1]
W. Walravens et al., “Setting carriers free : healing faulty interfaces promotes delocalization and transport in nanocrystal solids,” ACS NANO, vol. 13, no. 11, pp. 12774–12786, 2019.
@article{8637741,
  abstract     = {Superlattices of epitaxially connected nanocrystals (NCs) are model systems to study electronic and optical properties of NC arrays. Using elemental analysis and structural analysis by in situ X-ray fluorescence and grazing-incidence small-angle scattering, respectively, we show that epitaxial superlattices of PbSe NCs keep their structural integrity up to temperatures of 300 degrees C; an ideal starting point to assess the effect of gentle thermal annealing on the superlattice properties. We find that annealing such superlattices between 75 and 150 degrees C induces a marked red shift of the NC band-edge transition. In fact, the post-annealing band-edge reflects theoretical predictions on the impact of charge carrier delocalization in these epitaxial superlattices. In addition, we observe a pronounced enhancement of the charge carrier mobility and a reduction of the hopping activation energy after mild annealing. While the superstructure remains intact at these temperatures, structural defect studies through X-ray diffraction indicate that annealing markedly decreases the density of point defects and edge dislocations. This indicates that the connections between NCs in as-synthesized superlattices still form a major source of grain boundaries and defects, which prevent carrier delocalization over multiple NCs and hamper NC-to-NC transport. Overcoming the limitations imposed by interfacial defects is therefore an essential next step in the development of high-quality optoelectronic devices based on NC solids.},
  author       = {Walravens, Willem and Solano, Eduardo and Geenen, Filip and Dendooven, Jolien and Gorobtsov, Oleg and Tadjine, Athmane and Mahmoud, Nayyera and Ding, Patrick Peiwen and Ruff, Jacob P. C. and Singer, Andrej and Roelkens, Günther and Delerue, Christophe and Detavernier, Christophe and Hens, Zeger},
  issn         = {1936-0851},
  journal      = {ACS NANO},
  keywords     = {nanomaterials,self-assembly,nanocrystal solids,charge transport,grain boundary,nanocrystal-nanocrystal interface,defects,QUANTUM,ASSEMBLIES,PBS},
  language     = {eng},
  number       = {11},
  pages        = {12774--12786},
  title        = {Setting carriers free : healing faulty interfaces promotes delocalization and transport in nanocrystal solids},
  url          = {http://dx.doi.org/10.1021/acsnano.9b04757},
  volume       = {13},
  year         = {2019},
}

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