Perovskite superstructures and heterostructures for enhanced optical performance

Perovskites as a material class have attracted immense research attention due to its highly tunable emissions, narrow full width at half maximum, high photoluminescence quantum yields, broad absorption spectra, defect tolerance, and large carrier diffusion length. While much progress has been accomp...

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Main Author: Chan, Wen Kiat
Other Authors: Timothy Tan
Format: Thesis-Doctor of Philosophy
Language:English
Published: Nanyang Technological University 2023
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Online Access:https://hdl.handle.net/10356/172417
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Institution: Nanyang Technological University
Language: English
id sg-ntu-dr.10356-172417
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institution Nanyang Technological University
building NTU Library
continent Asia
country Singapore
Singapore
content_provider NTU Library
collection DR-NTU
language English
topic Engineering::Materials::Photonics and optoelectronics materials
spellingShingle Engineering::Materials::Photonics and optoelectronics materials
Chan, Wen Kiat
Perovskite superstructures and heterostructures for enhanced optical performance
description Perovskites as a material class have attracted immense research attention due to its highly tunable emissions, narrow full width at half maximum, high photoluminescence quantum yields, broad absorption spectra, defect tolerance, and large carrier diffusion length. While much progress has been accomplished in perovskite research, two areas are relatively unexplored and will be the focus of this thesis. The first is perovskite superstructures (SSs), which have only been reported as recently as 2018. Studies on perovskite SSs are gradually garnering attention as perovskite SSs allow for the electronic coupling of their constituent nanocrystals (NCs), allowing for the interdot effect and superradiant burst emissions. The second area is the formation of heterostructures, which allow for the combination of two different materials with complementary optical properties. For instance, combining lanthanide nanoparticles (LnNPs) with perovskites allows for enhanced absorption and two-way energy transfer. The first project in this thesis addresses the mechanism of perovskite SS formation which has thus far have not been studied in detail. In this work, CsPbBr3 perovskites were synthesized using different experiment conditions and quantities of PbBr2 precursor, and the total red-shift of the resulting samples were analysed to quantify the formation of perovskite SSs. From this study, we found that PbBr2 plays a critical role in CsPbBr3 SS formation. Since PbBr2 occupies Br vacancies naturally occurring on CsPbBr3 NCs, we proposed a possible SS formation mechanism where PbBr2 serves as a ‘glue’ linking together individual NCs to form SSs at higher PbBr2 concentrations. At lower PbBr2 concentrations the CsPbBr3 SSs demerge into individual CsPbBr3 NCs. The second project for this thesis addresses the formation of hybrid organic-inorganic perovskite SSs. Studies involving perovskite SSs mainly focus on all-inorganic CsPbBr3 synthesized using either the hot injection or ultrasonication methods. Hybrid perovskites involving cations such as MA and FA are valuable for their ultrapure green emissions and have been used for the highest performance perovskite solar cells. In this work, MA/FA/CsPbBr3 perovskite SSs were synthesized using the more scalable and facile ligand-assisted reprecipitation (LARP) method, demonstrating both the existence of hybrid perovskite SSs and the potential of the LARP method in obtaining perovskite SSs. The SSs drop-casted onto thin films produce ultrapure green emissions, demonstrating the potential for device fabrication in display applications. The last work of thesis focuses on the formation of LnNP@perovskite core-shell heterostructures. Lead halide perovskites and lanthanide ions have complementary absorption spectra and combining them allows for multiple energy transfer pathways depending on the permutation used. The formation of LnNP@perovskite heterostructures is rarely reported due to the challenges in overcoming the lattice mismatch between LnNPs and perovskites. In this thesis, we present a strategy to overcome the lattice mismatch by using ultrasmall LnNPs to seed the growth of perovskites, resulting in LnNP@perovskite heterostructures. The heterostructures demonstrated two-way energy transfer and could be activated with ultraviolet or near-infrared light. In conclusion, this thesis provided insights into perovskite SS formation, developed hybrid SS perovskites with ultrapure green emissions, and highlighted a strategy to overcome the lattice mismatch to form LnNP@perovskite heterostructures. While there is a lot more to be explored and learned, we hope that this work will contribute to the further development of perovskite devices with enhanced optical performance.
author2 Timothy Tan
author_facet Timothy Tan
Chan, Wen Kiat
format Thesis-Doctor of Philosophy
author Chan, Wen Kiat
author_sort Chan, Wen Kiat
title Perovskite superstructures and heterostructures for enhanced optical performance
title_short Perovskite superstructures and heterostructures for enhanced optical performance
title_full Perovskite superstructures and heterostructures for enhanced optical performance
title_fullStr Perovskite superstructures and heterostructures for enhanced optical performance
title_full_unstemmed Perovskite superstructures and heterostructures for enhanced optical performance
title_sort perovskite superstructures and heterostructures for enhanced optical performance
publisher Nanyang Technological University
publishDate 2023
url https://hdl.handle.net/10356/172417
_version_ 1784855616370507776
spelling sg-ntu-dr.10356-1724172023-12-08T08:16:55Z Perovskite superstructures and heterostructures for enhanced optical performance Chan, Wen Kiat Timothy Tan School of Chemistry, Chemical Engineering and Biotechnology TYTan@ntu.edu.sg Engineering::Materials::Photonics and optoelectronics materials Perovskites as a material class have attracted immense research attention due to its highly tunable emissions, narrow full width at half maximum, high photoluminescence quantum yields, broad absorption spectra, defect tolerance, and large carrier diffusion length. While much progress has been accomplished in perovskite research, two areas are relatively unexplored and will be the focus of this thesis. The first is perovskite superstructures (SSs), which have only been reported as recently as 2018. Studies on perovskite SSs are gradually garnering attention as perovskite SSs allow for the electronic coupling of their constituent nanocrystals (NCs), allowing for the interdot effect and superradiant burst emissions. The second area is the formation of heterostructures, which allow for the combination of two different materials with complementary optical properties. For instance, combining lanthanide nanoparticles (LnNPs) with perovskites allows for enhanced absorption and two-way energy transfer. The first project in this thesis addresses the mechanism of perovskite SS formation which has thus far have not been studied in detail. In this work, CsPbBr3 perovskites were synthesized using different experiment conditions and quantities of PbBr2 precursor, and the total red-shift of the resulting samples were analysed to quantify the formation of perovskite SSs. From this study, we found that PbBr2 plays a critical role in CsPbBr3 SS formation. Since PbBr2 occupies Br vacancies naturally occurring on CsPbBr3 NCs, we proposed a possible SS formation mechanism where PbBr2 serves as a ‘glue’ linking together individual NCs to form SSs at higher PbBr2 concentrations. At lower PbBr2 concentrations the CsPbBr3 SSs demerge into individual CsPbBr3 NCs. The second project for this thesis addresses the formation of hybrid organic-inorganic perovskite SSs. Studies involving perovskite SSs mainly focus on all-inorganic CsPbBr3 synthesized using either the hot injection or ultrasonication methods. Hybrid perovskites involving cations such as MA and FA are valuable for their ultrapure green emissions and have been used for the highest performance perovskite solar cells. In this work, MA/FA/CsPbBr3 perovskite SSs were synthesized using the more scalable and facile ligand-assisted reprecipitation (LARP) method, demonstrating both the existence of hybrid perovskite SSs and the potential of the LARP method in obtaining perovskite SSs. The SSs drop-casted onto thin films produce ultrapure green emissions, demonstrating the potential for device fabrication in display applications. The last work of thesis focuses on the formation of LnNP@perovskite core-shell heterostructures. Lead halide perovskites and lanthanide ions have complementary absorption spectra and combining them allows for multiple energy transfer pathways depending on the permutation used. The formation of LnNP@perovskite heterostructures is rarely reported due to the challenges in overcoming the lattice mismatch between LnNPs and perovskites. In this thesis, we present a strategy to overcome the lattice mismatch by using ultrasmall LnNPs to seed the growth of perovskites, resulting in LnNP@perovskite heterostructures. The heterostructures demonstrated two-way energy transfer and could be activated with ultraviolet or near-infrared light. In conclusion, this thesis provided insights into perovskite SS formation, developed hybrid SS perovskites with ultrapure green emissions, and highlighted a strategy to overcome the lattice mismatch to form LnNP@perovskite heterostructures. While there is a lot more to be explored and learned, we hope that this work will contribute to the further development of perovskite devices with enhanced optical performance. Doctor of Philosophy 2023-12-08T08:16:55Z 2023-12-08T08:16:55Z 2023 Thesis-Doctor of Philosophy Chan, W. K. (2023). Perovskite superstructures and heterostructures for enhanced optical performance. Doctoral thesis, Nanyang Technological University, Singapore. https://hdl.handle.net/10356/172417 https://hdl.handle.net/10356/172417 en RG128/19 (S) MOE 2016-T3-1-004 EDUNC-33-18-279-V12 This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License (CC BY-NC 4.0). Nanyang Technological University