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3. Photophysics of two-dimensional perovskites -- learning from metal halide substitution

Author

Kahmann, Simon, Duim, Herman, Fang, Hong-Hua, Dyksik, Mateusz, Adjokatse, Sampson, Medina, Martha Rivera, Pitaro, Matteo, Plochocka, Paulina, and Loi, Maria A.

Subjects
Condensed Matter - Materials Science
Abstract

Whereas their photophysics exhibits an intricate interplay of carriers with the lattice, most reports have so far relied on single compound studies. With the exception of variations of the organic spacer cations, the effect of constituent substitution on the photophysics and the nature of emitting species, in particular, has remained largely under-explored. Here PEA$_2$PbBr$_4$, PEA$_2$PbI$_4$, and PEA$_2$SnI$_4$ are studied through a variety of optical spectroscopy techniques to reveal a complex set of excitonic transitions at low temperature. We attribute the emergence of weak high energy features to a vibronic progression breaking Kasha's rule and highlight that the responsible phonons cannot be accessed through simple Raman spectroscopy. Bright peaks at lower energy are due to two distinct excitons, of which the upper is a convolution of a bright exciton and a localised state, whereas the lower is attributed to shallow defects. Our study offers deeper insights into the photophysics of two-dimensional perovskites through compositional substitution and highlights critical limits to the communities' current understanding of the photophysics of these compounds.

Published
2021
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4. Band-edge Exciton Fine Structure and Exciton Recombination Dynamics in Single crystals of Layered Hybrid Perovskites

Author

Fang, Hong-Hua, Yang, Jie, Adjokatse, Sampson, Kamminga, Machteld E., Duim, Herman, Ye, Jianting, Blake, Graeme R., Even, Jacky, and Loi, Maria Antonietta

Subjects
Condensed Matter - Materials Science
Abstract

Two-dimensional (2D) perovskite materials have recently re-attracted intense research interest for applications in photovoltaics and optoelectronics. As a consequence of the dielectric and quantum confinement effect, they show strongly bound and stable excitons at room temperature. In this report, the band-edge exciton fine structure and in particular its exciton and biexciton dynamics in high quality crystals of (PEA)2PbI4 are investigated. A comparison of bulk and surface exciton lifetimes yields a room temperature surface recombination velocity of 2x10^3cm/s and an intrinsic lifetime of 185ns. Biexciton emission is evidenced at room temperature, with binding energy of about 45meV and a lifetime of 80ps. At low temperature, exciton state splitting is observed, which is caused by the electron-hole exchange interaction. Transient photoluminescence resolves the low-lying dark exciton state, with a bright/dark splitting energy estimated to be 10meV. This work contributes to understand the complex scenario of the elementary photoexcitations in 2D perovskites., Comment: 15 Pages, 5 Figures and supplementary material

Published
2019

9. Unraveling the Broadband Emission in Mixed Tin-Lead Layered Perovskites

Author

Fang, Hong Hua, Tekelenburg, Eelco K., Xue, Haibo, Kahmann, Simon, Chen, Lijun, Adjokatse, Sampson, Brocks, Geert, Tao, Shuxia, Loi, Maria Antonietta, Fang, Hong Hua, Tekelenburg, Eelco K., Xue, Haibo, Kahmann, Simon, Chen, Lijun, Adjokatse, Sampson, Brocks, Geert, Tao, Shuxia, and Loi, Maria Antonietta

Abstract

Low-dimensional halide perovskites with broad emission are a hot topic for their promising application as white light sources. However, the physical origin of this broadband emission in the sub-bandgap region is still controversial. This work investigates the broad Stokes-shifted emission bands in mixed lead-tin 2D perovskite films prepared by mixing precursor solutions of phenethylammonium lead iodide (PEA2PbI4, PEA = phenethylammonium) and phenethylammonium tin iodide (PEA2SnI4). The bandgap can be tuned by the lead-tin ratio, whereas the photoluminescence is broad and significantly Stokes-shifted and appears to be fairly insensitive to the relative amount of Pb and Sn. It is experimentally observed that these low-dimensional systems show substantially less bandgap bowing than their 3D counterpart. Theoretically, this can be attributed to the smaller spin–orbit coupling effect on the 2D perovskites compared to that of 3D ones. The time-resolved photoluminescence shows an ultrafast decay in the high-energy range of the spectra that coincides with the emission range of PEA2SnI4, while the broadband emission decay is slower, up to the microsecond range. Sub-gap photoexcitation experiments exclude exciton self-trapping as the origin of the broadband emission, pointing to defects as the origin of the broadband emission in 2D Sn/Pb perovskite alloys.

Published
2023

10. Long Exciton Diffusion Length in High Mobility Emissive Organic Semiconductor

Author

Zhang, Yu, Yuan, Yong, Wang, Pu, Gao, Haikuo, Qin, Zhengsheng, Liu, Dan, Zhang, Xiaotao, Gao, Can, Fang, Hong-Hua, Hu, Wenping, and Dong, Huanli

Abstract

Organic semiconductors that possess both long exciton diffusion length and high mobility emissive properties are crucial for the development of high-performance organic optoelectronic devices. However, materials with these combined characteristics are currently rare. Herein, a long exciton diffusion length was obtained in the high mobility emissive organic semiconductor trans-1,2-bis(5-phenyldithieno[2,3-b:3′,2′-d]thiophen-2-yl)ethene (BPTTE). Excellent optoelectronic properties with the maximum carrier mobility of 18.1 cm2V–1s–1and high photoluminescence quantum yield (PLQY) of 21.4% were obtained for BPTTE single crystals. Notably, an impressive exciton diffusion length reaching up to 114.2 nm was also achieved, demonstrating the effective integration of optoelectrical properties in BPTTE single crystals. This work offers valuable guidance for exploring the multifunctional capabilities of high mobility organic semiconductors, a crucial aspect for enhancing the performance of organic optoelectronic devices.

Published
2024
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12. All-Optical Reconfigurable Excitonic Charge States in Monolayer MoS2

Author

Huang, Guan-Yao, primary, Lin, Linhan, additional, Zhao, Shuang, additional, Li, Wenbin, additional, Deng, Xiaonan, additional, Zhang, Simian, additional, Wang, Chen, additional, Li, Xiao-Ze, additional, Zhang, Yan, additional, Fang, Hong-Hua, additional, Zou, Yixuan, additional, Li, Peng, additional, Bai, Benfeng, additional, Sun, Hong-Bo, additional, and Fu, Tairan, additional

Published
2023
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15. Highly Fluorescent Semiconducting Two-Dimensional Conjugated Polymer Films Achieved by Side-Chain Engineering Showing Large Exciton Diffusion Length

Author

Wang, Yongshuai, primary, Zhang, Qing, additional, Li, Xiao-Ze, additional, Shu, Zhibin, additional, Zhang, Yihan, additional, Gao, Can, additional, Li, Yang, additional, Liu, Hao, additional, Li, Chenguang, additional, Fang, Hong-Hua, additional, Sun, Hong-Bo, additional, Zhang, Xiaotao, additional, Hu, Wenping, additional, and Dong, Huanli, additional

Published
2022
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23. Reversible Three‐Color Fluorescence Switching of an Organic Molecule in the Solid State via “Pump–Trigger” Optical Manipulation

Author

Yang, Runqing, primary, Ren, Xue, additional, Mei, Lijun, additional, Pan, Guocui, additional, Li, Xiao‐Ze, additional, Wu, Zhiyuan, additional, Zhang, Song, additional, Ma, Wenyue, additional, Yu, Weili, additional, Fang, Hong‐Hua, additional, Li, Chong, additional, Zhu, Ming‐Qiang, additional, Hu, Zheng, additional, Sun, Tianmeng, additional, Xu, Bin, additional, and Tian, Wenjing, additional

Published
2022
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26. Unraveling the Broadband Emission in Mixed Tin‐Lead Layered Perovskites.

Author

Fang, Hong‐Hua, Tekelenburg, Eelco K., Xue, Haibo, Kahmann, Simon, Chen, Lijun, Adjokatse, Sampson, Brocks, Geert, Tao, Shuxia, and Loi, Maria Antonietta

Subjects
*MIXING height (Atmospheric chemistry), *LIGHT sources, *SPIN-orbit interactions, *PEROVSKITE, *LEAD iodide, *CESIUM compounds
Abstract

Low‐dimensional halide perovskites with broad emission are a hot topic for their promising application as white light sources. However, the physical origin of this broadband emission in the sub‐bandgap region is still controversial. This work investigates the broad Stokes‐shifted emission bands in mixed lead‐tin 2D perovskite films prepared by mixing precursor solutions of phenethylammonium lead iodide (PEA2PbI4, PEA = phenethylammonium) and phenethylammonium tin iodide (PEA2SnI4). The bandgap can be tuned by the lead‐tin ratio, whereas the photoluminescence is broad and significantly Stokes‐shifted and appears to be fairly insensitive to the relative amount of Pb and Sn. It is experimentally observed that these low‐dimensional systems show substantially less bandgap bowing than their 3D counterpart. Theoretically, this can be attributed to the smaller spin–orbit coupling effect on the 2D perovskites compared to that of 3D ones. The time‐resolved photoluminescence shows an ultrafast decay in the high‐energy range of the spectra that coincides with the emission range of PEA2SnI4, while the broadband emission decay is slower, up to the microsecond range. Sub‐gap photoexcitation experiments exclude exciton self‐trapping as the origin of the broadband emission, pointing to defects as the origin of the broadband emission in 2D Sn/Pb perovskite alloys. [ABSTRACT FROM AUTHOR]

Published
2023
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31. Laser Writing of Color Centers.

Author

Wang, Xiao‐Jie, Fang, Hong‐Hua, Sun, Fang‐Wen, and Sun, Hong‐Bo

Subjects
*WRITING centers, *QUANTUM computing, *ION bombardment, *ION implantation, *QUANTUM dots, *CARBON nanotubes
Abstract

Color centers, optically active defects within solids, are vital for leading quantum information technologies such as quantum computing and quantum sensing. An essential prerequisite for realizing scalable quantum architectures is the ability to create quantum emitters deterministically. In the last decades, significant efforts have been devoted to selectively generating color centers. One of the most used methods is high‐energy ion implantation. However, this method usually causes extended lattice damage along the entire trajectory because of ions bombardment. Moreover, the position depth of color centers is also limited by the ions penetrate length in crystals. The direct laser‐writing (DLW) technique has recently emerged as a powerful tool to create color centers in solid‐state materials. It can define color centers at arbitrary depths inside the substrate and operate at the ambient environment, therefore, providing a feasible 3D fabrication method for integrated quantum photonics. Here, recent advancements of laser writing of color centers in solid‐state materials are reviewed, from bulk crystals, such as diamond and silicon carbide, to nanostructures, involving single‐walled carbon nanotubes, 2D layered materials, and quantum dots. [ABSTRACT FROM AUTHOR]

Published
2022
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33. Multiband electronic transitions in 2D and 3D hybrid perovskites: recent results

Author

Even, Jacky, Tsai, Hsinhan, Nie, Wanyie, Neukirch, Amanda, Blancon, Jean-Christophe, Pedesseau, Laurent, Durand, Olivier, Traoré, Boubacar, Kepenekian, Mikael, Stoumpos, Constantinos, Tamarat, Philippe, Lounis, Brahim, Sfeir, Matthew, Fang, Hong-Hua, Shen, Qing, Loi, Maria Antonietta, Hayaze, Shuzi, Crochet, Jared, Tretiak, Sergei, Kanatzidis, Mercouri, Mohite, Aditya, Katan, Claudine, Institut des Fonctions Optiques pour les Technologies de l'informatiON (Institut FOTON), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA)-École Nationale Supérieure des Sciences Appliquées et de Technologie (ENSSAT)-Centre National de la Recherche Scientifique (CNRS)-IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT), Los Alamos National Laboratory (LANL), Rice University [Houston], Institut des Sciences Chimiques de Rennes (ISCR), Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Ecole Nationale Supérieure de Chimie de Rennes (ENSCR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA), Northwestern University [Evanston], Laboratoire Photonique, Numérique et Nanosciences (LP2N), Université de Bordeaux (UB)-Institut d'Optique Graduate School (IOGS)-Centre National de la Recherche Scientifique (CNRS), Brookhaven National Laboratory [Upton, NY] (BNL), U.S. Department of Energy [Washington] (DOE)-UT-Battelle, LLC-Stony Brook University [SUNY] (SBU), State University of New York (SUNY)-State University of New York (SUNY), Zernike Institute for Advanced Materials, University of Groningen [Groningen], Department of Electronic Engineering [Tokyo], University of Electro-Communications [Tokyo] (UEC), Kyushu Institute of Technology, Université de Rennes (UR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-École Nationale Supérieure des Sciences Appliquées et de Technologie (ENSSAT)-Centre National de la Recherche Scientifique (CNRS), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Ecole Nationale Supérieure de Chimie de Rennes (ENSCR)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), UT-Battelle, LLC-Stony Brook University [SUNY] (SBU), State University of New York (SUNY)-State University of New York (SUNY)-U.S. Department of Energy [Washington] (DOE), and Kyushu Institute of Technology (Kyutech)

Subjects
[PHYS]Physics [physics], [CHIM]Chemical Sciences, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2018

34. Stable Cesium Formamidinium Lead Halide Perovskites: A Comparison of Photophysics and Phase Purity in Thin Films and Single Crystals

Author

Groeneveld, Bart G. H. M., primary, Adjokatse, Sampson, additional, Nazarenko, Olga, additional, Fang, Hong-Hua, additional, Blake, Graeme R., additional, Portale, Giuseppe, additional, Duim, Herman, additional, ten Brink, Gert H., additional, Kovalenko, Maksym V., additional, and Loi, Maria Antonietta, additional

Published
2019
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39. Unravelling light-induced degradation of layered perovskite crystals and design of efficient encapsulation for improved photostability

Author

Fang, Hong Hua, Yang, Jie, Tao, S.X., Adjokatse, Sampson, Kamminga, Machteld, Ye, Jianting, Blake, Graeme, Even, Jacky, Loi, Maria, Fang, Hong Hua, Yang, Jie, Tao, S.X., Adjokatse, Sampson, Kamminga, Machteld, Ye, Jianting, Blake, Graeme, Even, Jacky, and Loi, Maria

Abstract

Layered halide perovskites have recently shown extraordinary potential for low-cost solution-processable optoelectronic applications because of their superior moisture stability over their 3D counterparts. However, few studies have investigated the effect of light on layered hybrid perovskites. Here, the mechanically exfoliated nanoflakes of the 2D perovskite (PEA) 2PbI 4 (PEA, 2-phenylethylammonium) are used as a model to investigate their intrinsic photostability. The light-induced degradation of the flakes is investigated by using in situ techniques including confocal laser scanning microscopy, wide-field fluorescence microscopy, and atomic force microscopy. Under resonant photoexcitation, (PEA) 2PbI 4 degrades to PbI 2. It is clearly shown that this process is initiated at the crystal edges and from the surface. As a consequence, the photoluminescence of (PEA) 2PbI 4 is progressively quenched by surface traps. Importantly, the light-induced degradation can be suppressed by encapsulation using hexagonal boron nitride (hBN) flakes and/or polycarbonates. This report sheds light on a specific mechanism of light-induced degradation in layered perovskites and proposes a new encapsulation method to improve their photostability.

Published
2018

40. Stable Cesium Formamidinium Lead Halide Perovskites: A Comparison of Photophysics and Phase Purity in Thin Films and Single Crystals.

Author

Groeneveld, Bart G. H. M., Adjokatse, Sampson, Nazarenko, Olga, Fang, Hong-Hua, Blake, Graeme R., Portale, Giuseppe, Duim, Herman, ten Brink, Gert H., Kovalenko, Maksym V., and Loi, Maria Antonietta

Subjects
CESIUM compounds, THIN films, SINGLE crystals, LEAD halides, CHARGE carrier lifetime, PEROVSKITE, CESIUM, SILICON compounds
Abstract

The stability of the active layer is an underinvestigated aspect of metal halide perovskite solar cells. Furthermore, the few articles on the subject are typically focused on thin films, which are complicated by the presence of defects and grain boundaries. Herein, a different approach is taken: a perovskite composition that is known to be stable in single crystal form is used, and its (photo‐)physical properties are studied in the form of spin‐coated thin films. The perovskites are lead‐based with cesium and formamidinium as the A‐site cations and iodide and bromide as the halide anions, with the formula Cs0.1FA0.9PbI3−xBrx. These compounds show high potential in terms of stability in single crystal form and closely resemble the compounds that have successfully been used in highly efficient perovskite–silicon tandem solar cells. It is found that a small difference in bromine content (x = 0.45 vs 0.6) has a significant impact in terms of the phase purity and charge carrier lifetimes, and conclude that the thin films of Cs0.1FA0.9PbI2.55Br0.45 have good potential for the use in optoelectronic devices. [ABSTRACT FROM AUTHOR]

Published
2020
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41. Band‐Edge Exciton Fine Structure and Exciton Recombination Dynamics in Single Crystals of Layered Hybrid Perovskites.

Author

Fang, Hong‐Hua, Yang, Jie, Adjokatse, Sampson, Tekelenburg, Eelco, Kamminga, Machteld E., Duim, Herman, Ye, Jianting, Blake, Graeme R., Even, Jacky, and Loi, Maria Antonietta

Subjects
*EXCITON theory, *SINGLE crystals, *QUANTUM confinement effects, *SURFACE recombination, *DARK energy
Abstract

2D perovskite materials have recently reattracted intense research interest for applications in photovoltaics and optoelectronics. As a consequence of the dielectric and quantum confinement effect, they show strongly bound and stable excitons at room temperature. Here, the band‐edge exciton fine structure and in particular its exciton and biexciton dynamics in high quality crystals of (PEA)2PbI4 are investigated. A comparison of bulk and surface exciton lifetimes yields a room temperature surface recombination velocity of 2 × 103 cm s−1 and an intrinsic lifetime of 185 ns. Biexciton emission is evidenced at room temperature, with a binding energy of ≈45 meV and a lifetime of 80 ps. At low temperature, exciton state splitting is observed, which is caused by the electron–hole exchange interaction. Transient photoluminescence resolves the low‐lying dark exciton state, with a bright/dark splitting energy estimated to be 10 meV. This work contributes to the understanding of the complex scenario of the elementary photoexcitations in 2D perovskites. [ABSTRACT FROM AUTHOR]

Published
2020
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43. Clarification of the Molecular Doping Mechanism in Organic Single-Crystalline Semiconductors and their Application in Color-Tunable Light-Emitting Devices

Author

Ding, Ran, primary, Wang, Xue-Peng, additional, Feng, Jing, additional, Li, Xian-Bin, additional, Dong, Feng-Xi, additional, Tian, Wei-Quan, additional, Du, Jia-Ren, additional, Fang, Hong-Hua, additional, Wang, Hai-Yu, additional, Yamao, Takeshi, additional, Hotta, Shu, additional, and Sun, Hong-Bo, additional

Published
2018
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50. Layered/3D Halide Hybrid Perovskite Semiconductors: Advances and Promises

Author

Pedesseau, Laurent, primary, Kepenekian, Mikael, additional, Traore, Boubacar, additional, Robles, Roberto, additional, Fang, Hong Hua, additional, Loi, Maria A, additional, Tsai, Hsinhan, additional, Sapori, Daniel, additional, Blancon, Jean Christophe, additional, Neukirch, Amanda, additional, Tretiak, Sergei, additional, Mohite, Aditya, additional, Katan, Claudine, additional, Even, Jacky, additional, and Nie, Wanyi, additional

Published
2017
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