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Band Gap Tuning of Films of Undoped ZnO Nanocrystals by Removal of Surface Groups
Transparent conductive oxides (TCOs) are widely used in optoelectronic devices such as flat-panel displays and solar cells. A significant optical property of TCOs is their band gap, which determines the spectral range of the transparency of the material. In this study, a tunable band gap range from...
Autores principales: | , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
MDPI
2022
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8838492/ https://www.ncbi.nlm.nih.gov/pubmed/35159909 http://dx.doi.org/10.3390/nano12030565 |
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author | Zhang, Chengjian Tu, Qiaomiao Francis, Lorraine F. Kortshagen, Uwe R. |
author_facet | Zhang, Chengjian Tu, Qiaomiao Francis, Lorraine F. Kortshagen, Uwe R. |
author_sort | Zhang, Chengjian |
collection | PubMed |
description | Transparent conductive oxides (TCOs) are widely used in optoelectronic devices such as flat-panel displays and solar cells. A significant optical property of TCOs is their band gap, which determines the spectral range of the transparency of the material. In this study, a tunable band gap range from 3.35 eV to 3.53 eV is achieved for zinc oxide (ZnO) nanocrystals (NCs) films synthesized by nonthermal plasmas through the removal of surface groups using atomic layer deposition (ALD) coating of Al(2)O(3) and intense pulsed light (IPL) photo-doping. The Al(2)O(3) coating is found to be necessary for band gap tuning, as it protects ZnO NCs from interactions with the ambient and prevents the formation of electron traps. With respect to the solar spectrum, the 0.18 eV band gap shift would allow ~4.1% more photons to pass through the transparent layer, for instance, into a CH(3)NH(3)PbX(3) solar cell beneath. The mechanism of band gap tuning via photo-doping appears to be related to a combination of the Burstein–Moss (BM) and band gap renormalization (BGN) effects due to the significant number of electrons released from trap states after the removal of hydroxyl groups. The BM effect shifts the conduction band edge and enlarges the band gap, while the BGN effect narrows the band gap. |
format | Online Article Text |
id | pubmed-8838492 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2022 |
publisher | MDPI |
record_format | MEDLINE/PubMed |
spelling | pubmed-88384922022-02-13 Band Gap Tuning of Films of Undoped ZnO Nanocrystals by Removal of Surface Groups Zhang, Chengjian Tu, Qiaomiao Francis, Lorraine F. Kortshagen, Uwe R. Nanomaterials (Basel) Article Transparent conductive oxides (TCOs) are widely used in optoelectronic devices such as flat-panel displays and solar cells. A significant optical property of TCOs is their band gap, which determines the spectral range of the transparency of the material. In this study, a tunable band gap range from 3.35 eV to 3.53 eV is achieved for zinc oxide (ZnO) nanocrystals (NCs) films synthesized by nonthermal plasmas through the removal of surface groups using atomic layer deposition (ALD) coating of Al(2)O(3) and intense pulsed light (IPL) photo-doping. The Al(2)O(3) coating is found to be necessary for band gap tuning, as it protects ZnO NCs from interactions with the ambient and prevents the formation of electron traps. With respect to the solar spectrum, the 0.18 eV band gap shift would allow ~4.1% more photons to pass through the transparent layer, for instance, into a CH(3)NH(3)PbX(3) solar cell beneath. The mechanism of band gap tuning via photo-doping appears to be related to a combination of the Burstein–Moss (BM) and band gap renormalization (BGN) effects due to the significant number of electrons released from trap states after the removal of hydroxyl groups. The BM effect shifts the conduction band edge and enlarges the band gap, while the BGN effect narrows the band gap. MDPI 2022-02-07 /pmc/articles/PMC8838492/ /pubmed/35159909 http://dx.doi.org/10.3390/nano12030565 Text en © 2022 by the authors. https://creativecommons.org/licenses/by/4.0/Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/). |
spellingShingle | Article Zhang, Chengjian Tu, Qiaomiao Francis, Lorraine F. Kortshagen, Uwe R. Band Gap Tuning of Films of Undoped ZnO Nanocrystals by Removal of Surface Groups |
title | Band Gap Tuning of Films of Undoped ZnO Nanocrystals by Removal of Surface Groups |
title_full | Band Gap Tuning of Films of Undoped ZnO Nanocrystals by Removal of Surface Groups |
title_fullStr | Band Gap Tuning of Films of Undoped ZnO Nanocrystals by Removal of Surface Groups |
title_full_unstemmed | Band Gap Tuning of Films of Undoped ZnO Nanocrystals by Removal of Surface Groups |
title_short | Band Gap Tuning of Films of Undoped ZnO Nanocrystals by Removal of Surface Groups |
title_sort | band gap tuning of films of undoped zno nanocrystals by removal of surface groups |
topic | Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8838492/ https://www.ncbi.nlm.nih.gov/pubmed/35159909 http://dx.doi.org/10.3390/nano12030565 |
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