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13 results on '"Ijaz, Palvasha"'

1. Composition, Size, and Surface Functionalization dependent Optical Properties of Lead Bromide Perovskite Nanocrystals

Author

Ijaz, Palvasha, Imran, Muhammad, Soares, Márcio M., Tolentino, Hélio C. N., Martín-García, Beatriz, Giannini, Cinzia, Moreels, Iwan, Manna, Liberato, and Krahne, Roman

Subjects
Physics - Chemical Physics
Abstract

The photoluminescence (PL), color purity, and stability of lead halide perovskite nanocrystals depend critically on the surface passivation. We present a study on the temperature dependent PL and PL decay dynamics of lead bromide perovskite nanocrystals characterized by different types of A cations, surface ligands, and nanocrystal sizes. Throughout, we observe a single emission peak from cryogenic to ambient temperature. The PL decay dynamics are dominated by the surface passivation, and a post-synthesis ligand exchange with a quaternary ammonium bromide (QAB) results in a more stable passivation over a larger temperature range. The PL intensity is highest from 50K-250K, which indicates that the ligand binding competes with the thermal energy at ambient temperature. Despite the favorable PL dynamics of nanocrystals passivated with QAB ligands (monoexponential PL decay over a large temperature range, increased PL intensity and stability), the surface passivation still needs improvement toward increased emission intensity in nanocrystal films., Comment: 19 pages, 5 figures

Published
2020
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2. Molecular‐Additive‐Assisted Tellurium Homogenization in ZnSeTe Quantum Dots

Author

Imran, Muhammad, primary, Paritmongkol, Watcharaphol, additional, Mills, Harrison A., additional, Hassan, Yasser, additional, Zhu, Tong, additional, Wang, Ya‐Kun, additional, Liu, Yuan, additional, Wan, Haoyue, additional, Park, So Min, additional, Jung, Euidae, additional, Tam, Jason, additional, Lyu, Quan, additional, Cotella, Giovanni Francesco, additional, Ijaz, Palvasha, additional, Chun, Peter, additional, and Hoogland, Sjoerd, additional

Published
2023
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10. Shape-Pure, Nearly Monodispersed CsPbBr3Nanocubes Prepared Using Secondary Aliphatic Amines

Author

Imran, Muhammad, Ijaz, Palvasha, Baranov, Dmitry, Goldoni, Luca, Petralanda, Urko, Akkerman, Quinten, Abdelhady, Ahmed L., Prato, Mirko, Bianchini, Paolo, Infante, Ivan, and Manna, Liberato

Abstract

Fully inorganic cesium lead halide perovskite (CsPbX3) nanocrystals (NCs) have been extensively studied due to their excellent optical properties, especially their high photoluminescence quantum yield (PLQY) and the ease with which the PL can be tuned across the visible spectrum. So far, most strategies for synthesizing CsPbX3NCs are highly sensitive to the processing conditions and ligand combinations. For example, in the synthesis of nanocubes of different sizes, it is not uncommon to have samples that contain various other shapes, such as nanoplatelets and nanosheets. Here, we report a new colloidal synthesis method for preparing shape-pure and nearly monodispersed CsPbBr3nanocubes using secondary amines. Regardless of the length of the alkyl chains, the oleic acid concentration, and the reaction temperature, only cube-shaped NCs were obtained. The shape purity and narrow size distribution of the nanocubes are evident from their sharp excitonic features and their ease of self-assembly in superlattices, reaching lateral dimensions of up to 50 μm. We attribute this excellent shape and phase purity to the inability of secondary amines to find the right steric conditions at the surface of the NCs, which consequently limits the formation of low-dimensional structures. Furthermore, no contamination from other phases was observed, not even from Cs4PbBr6, presumably due to the poor ability of secondary aliphatic amines to coordinate to PbBr2and, hence, to provide a reaction environment that is depleted in Pb.

Published
2018
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12. Shape-Pure, Nearly Monodispersed CsPbBr 3 Nanocubes Prepared Using Secondary Aliphatic Amines.

Author

Imran M, Ijaz P, Baranov D, Goldoni L, Petralanda U, Akkerman Q, Abdelhady AL, Prato M, Bianchini P, Infante I, and Manna L

Abstract

Fully inorganic cesium lead halide perovskite (CsPbX 3 ) nanocrystals (NCs) have been extensively studied due to their excellent optical properties, especially their high photoluminescence quantum yield (PLQY) and the ease with which the PL can be tuned across the visible spectrum. So far, most strategies for synthesizing CsPbX 3 NCs are highly sensitive to the processing conditions and ligand combinations. For example, in the synthesis of nanocubes of different sizes, it is not uncommon to have samples that contain various other shapes, such as nanoplatelets and nanosheets. Here, we report a new colloidal synthesis method for preparing shape-pure and nearly monodispersed CsPbBr 3 nanocubes using secondary amines. Regardless of the length of the alkyl chains, the oleic acid concentration, and the reaction temperature, only cube-shaped NCs were obtained. The shape purity and narrow size distribution of the nanocubes are evident from their sharp excitonic features and their ease of self-assembly in superlattices, reaching lateral dimensions of up to 50 μm. We attribute this excellent shape and phase purity to the inability of secondary amines to find the right steric conditions at the surface of the NCs, which consequently limits the formation of low-dimensional structures. Furthermore, no contamination from other phases was observed, not even from Cs 4 PbBr 6 , presumably due to the poor ability of secondary aliphatic amines to coordinate to PbBr 2 and, hence, to provide a reaction environment that is depleted in Pb.

Published
2018
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