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48 results on '"Tan, Zhi‐Kuang"'

1. Unidirectional Chiral Emission via Twisted Bi-layer Metasurfaces

Author

Gromyko, Dmitrii, An, Shu, Gorelik, Sergey, Xu, Jiahui, Lim, Li Jun, Lee, Henry Yit Loong, Tjiptoharsono, Febiana, Tan, Zhi-Kuang, Qiu, Cheng-Wei, Dong, Zhaogang, and Wu, Lin

Subjects
Physics - Optics
Abstract

Controlling and channelling light emissions from unpolarized quantum dots into specific directions with chiral polarization remains a key challenge in modern photonics. Stacked metasurface designs offer a potential compact solution for chirality and directionality engineering. However, experimental observations of directional chiral radiation from resonant metasurfaces with quantum emitters remain obscure. In this paper, we present experimental observations of unidirectional chiral emission from a twisted bi-layer metasurface via multi-dimensional control, including twist angle, interlayer distance, and lateral displacement between the top and bottom layers, as enabled by doublet alignment lithography (DAL). First, maintaining alignment, the metasurface demonstrates a resonant intrinsic optical chirality with near-unity circular dichroism of 0.94 and reflectance difference of 74%, where a high circular dichroism greater than 0.9 persists across a wide range of angles from -11 to 11 degrees. Second, engineered lateral displacement induces a unidirectional chiral resonance, resulting in unidirectional chiral emission from the quantum dots deposited onto the metasurface. Our bi-layer metasurfaces offer a universal compact platform for efficient radiation manipulation over a wide angular range, promising potential applications in miniaturized lasers, grating couplers, and chiral nanoantennas., Comment: 16 pages, 4 figures

Published
2024

2. Engineering Perovskite Emissions via Optical Quasi-Bound-States-in-the-Continuum

Author

Csányi, Evelin, Liu, Yan, Rezaei, Soroosh Daqiqeh, Lee, Henry Yit Loong, Tjiptoharsono, Febiana, Mahfoud, Zackaria, Gorelik, Sergey, Zhao, Xiaofei, Lim, Li Jun, Zhu, Di, Wu, Jing, Goh, Kuan Eng Johnson, Gao, Weibo, Tan, Zhi-Kuang, Leggett, Graham, Qiu, Cheng-Wei, and Dong, Zhaogang

Subjects
Physics - Optics, Physics - Applied Physics
Abstract

Metal halide perovskite quantum dots (PQDs) have emerged as promising materials due to their exceptional photoluminescence (PL) properties. A wide range of applications could benefit from adjustable luminescence properties, while preserving the physical and chemical properties of the PQDs. Therefore, post-synthesis engineering has gained attention recently, involving the use of ion-exchange or external stimuli, such as extreme pressure, magnetic and electric fields. Nevertheless, these methods typically suffer from spectrum broadening, intensity quenching or yield multiple bands. Alternatively, photonic antennas can modify the radiative decay channel of perovskites via the Purcell effect, with the largest wavelength shift being 8 nm to date, at an expense of 5-fold intensity loss. Here, we present an optical nanoantenna array with polarization-controlled quasi-bound-states-in-the-continuum (q-BIC) resonances, which can engineer and shift the photoluminescence wavelength over a ~39 nm range and confers a 21-fold emission enhancement of FAPbI3 perovskite QDs. The spectrum is engineered in a non-invasive manner via lithographically defined antennas and the pump laser polarization at ambient conditions. Our research provides a path towards advanced optoelectronic devices, such as spectrally tailored quantum emitters and lasers., Comment: 39 pages, 4 figures in the main text and 10 figures in the supporting information

Published
2023

5. Engineering and Controlling Perovskite Emissions via Optical Quasi‐Bound‐States‐in‐the‐Continuum.

Author

Csányi, Evelin, Liu, Yan, Rezaei, Soroosh Daqiqeh, Lee, Henry Yit Loong, Tjiptoharsono, Febiana, Mahfoud, Zackaria, Gorelik, Sergey, Zhao, Xiaofei, Lim, Li Jun, Zhu, Di, Wu, Jing, Goh, Kuan Eng Johnson, Gao, Weibo, Tan, Zhi‐Kuang, Leggett, Graham, Qiu, Cheng‐Wei, and Dong, Zhaogang

Subjects
AUTOMATIC control systems, ENGINEERS, LASER pumping, ELECTRIC fields, EMISSION control, PEROVSKITE
Abstract

Metal halide perovskite quantum dots (PQDs) have emerged as promising materials due to their exceptional photoluminescence (PL) properties. A wide range of applications could benefit from adjustable luminescence properties, while preserving the physical and chemical properties of the PQDs. Therefore, post‐synthesis engineering has gained attention recently, involving the use of ion‐exchange or external stimuli, such as extreme pressure, magnetic and electric fields. Nevertheless, these methods typically suffer from spectrum broadening, intensity quenching or yield multiple bands. Alternatively, photonic antennas can modify the radiative decay channel of perovskites via the Purcell effect, with the largest wavelength shift being 8 nm to date, at an expense of fivefold intensity loss. Here, this work presents an optical nanoantenna array with polarization‐controlled quasi‐bound‐states‐in‐the‐continuum resonances, which can engineer and shift the photoluminescence wavelength over a ≈39 nm range and confers a 21‐fold emission enhancement of FAPbI3 perovskite QDs. The spectrum is engineered in a non‐invasive manner via lithographically defined antennas and the pump laser polarization at ambient conditions. This research provides a path toward advanced optoelectronic devices, such as spectrally tailored quantum emitters and lasers. [ABSTRACT FROM AUTHOR]

Published
2024
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16. The Role of Subsurface Valence Band Localization in the Passivation of Perovskite Nanocrystals.

Author

Wang, Tian, Ng, Jun De Andrew, Ong, Evon Woan Yuann, Khoo, Khoong Hong, and Tan, Zhi‐Kuang

Subjects
NANOCRYSTALS, SEMICONDUCTOR nanocrystals, VALENCE bands, PASSIVATION, PEROVSKITE, CONDUCTION electrons, QUANTUM dots
Abstract

Traditional colloidal quantum dots rely on larger‐bandgap semiconductor shells for the localization of excitons in their emissive core. Unshelled quantum dots are typically weakly luminescent due to severe quenching by deep electronic traps. Lead halide perovskite nanocrystals deviate from this convention and require only common monofunctional aliphatic ligands on their surfaces to attain near‐unity luminescence quantum yields. Here, a combination of density functional theory calculations and experimental studies is employed to elucidate the mechanistic role of the ligands. The attachment of a surface ligand leads to a distortion of the surface, which results in the localization of the valence band deeper into the subsurface layers. This creates an energetic profile that is similar to a conventional core–shell quantum dot and renders the valence electrons unavailable for interaction with adventitious chemical species. It is further shown that a phosphonate moiety offers significantly stronger binding and leads to the long‐term preservation of this beneficial subsurface localized band structure. As experimental proof, a red‐emitting mixed‐halide perovskite nanocrystal, which is usually susceptible to degradation and spectral shifts, exhibits remarkable stability under a phosphonate ligand shell. These findings and mechanistic insights may guide the future engineering of robust perovskite nanocrystals for color displays and light‐emitting applications. [ABSTRACT FROM AUTHOR]

Published
2022
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22. Efficiency Measurements for 4-Terminal Perovskite/Silicon Tandem Solar Cells

Author

Thway, Maung, primary, Liu, Tianyuan, additional, Huang, Mei, additional, Dewi, Herlina Arianita, additional, Wang, Hao, additional, Xie, Chenchao, additional, Zhao, Xiaofei, additional, Tan, Zhi-Kuang, additional, Bruno, Annalisa, additional, Mhaisalkar, Subodh, additional, Chua, Soo Jin, additional, Aberle, Armin G., additional, Stangl, Rolf, additional, and Lin, Fen, additional

Published
2020
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32. Highly Efficient Perovskite Nanocrystal Light-Emitting Diodes Enabled by a Universal Crosslinking Method

Author

Li, Guangru, Rivarola, Florencia Wisnivesky Rocca, Davis, Nathaniel JLK, Bai, Sai, Jellicoe, Tom C, de la Peña, Francisco, Hou, Shaocong, Ducati, Caterina, Gao, Feng, Friend, Richard H, Greenham, Neil C, Tan, Zhi-Kuang, Ducati, Caterina [0000-0003-3366-6442], Friend, Richard [0000-0001-6565-6308], Greenham, Neil [0000-0002-2155-2432], and Apollo - University of Cambridge Repository

Subjects
nanocrystal, Atom and Molecular Physics and Optics, crosslinking, Atom- och molekylfysik och optik, passivation, perovskite light-emitting diodes
Abstract

The preparation of highly efficient perovskite nanocrystal light-emitting diodes is shown. A new trimethylaluminum vapor-based crosslinking method to render the nanocrystal films insoluble is applied. The resulting near-complete nanocrystal film coverage, coupled with the natural confinement of injected charges within the perovskite crystals, facilitates electron-hole capture and give rise to a remarkable electroluminescence yield of 5.7%. Funding Agencies|EPSRC [EP/M005143/1, EP/J017361/1, EP/G037221/1]; Gates Cambridge Trust; CNPq [246050/2012-8]; ERC [259619 PHOTO-EM]; EU [312483 ESTEEM2]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [200900971]; Cambridge Commonwealth European and International Trust; Cambridge Australian Scholarships

Published
2016

33. Enhanced performance in fluorene-free organometal halide perovskite light-emitting diodes using tunable, low electron affinity oxide electron injectors

Author

Hoye, Robert L Z, Chua, Matthew R, Musselman, Kevin P, Li, Guangru, Lai, May-Ling, Tan, Zhi-Kuang, Greenham, Neil C, MacManus-Driscoll, Judith L, Friend, Richard H, Credgington, Dan, Hoye, Robert [0000-0002-7675-0065], Greenham, Neil [0000-0002-2155-2432], Friend, Richard [0000-0001-6565-6308], Credgington, Daniel [0000-0003-4246-2118], and Apollo - University of Cambridge Repository

Subjects
electron injection barrier tuning, zinc magnesium oxide, polymer light-emitting diodes, spatial atmospheric atomic layer deposition, Communications, perovskite light-emitting diodes
Abstract

Fluorene-free perovskite light-emitting diodes (LEDs) with low turn-on voltages, higher luminance and sharp, color-pure electroluminescence are obtained by replacing the F8 electron injector with ZnO, which is directly deposited onto the CH3NH3PbBr3 perovskite using spatial atmospheric atomic layer deposition. The electron injection barrier can also be reduced by decreasing the ZnO electron affinity through Mg incorporation, leading to lower turn-on voltages.

Published
2015

34. Size-Dependent Photon Emission from Organometal Halide Perovskite Nanocrystals Embedded in an Organic Matrix

Author

Di, Dawei, Musselman, Kevin P, Li, Guangru, Sadhanala, Aditya, Ievskaya, Yulia, Song, Qilei, Tan, Zhi-Kuang, Lai, May Ling, MacManus-Driscoll, Judith L, Greenham, Neil C, Friend, Richard H, Di, Dawei [0000-0003-0703-2809], Sadhanala, Aditya [0000-0003-2832-4894], Greenham, Neil [0000-0002-2155-2432], Friend, Richard [0000-0001-6565-6308], and Apollo - University of Cambridge Repository

Subjects
Perovskite-organic blends, Nanocrystal growth, Self-assembly, Organometal halide perovskites, Band gap engineering, Photoluminescence
Abstract

In recent years, organometal halide perovskite materials have attracted significant research interest in the field of optoelectronics. Here, we introduce a simple and low-temperature route for the formation of self-assembled perovskite nanocrystals in a solid organic matrix. We demonstrate that the size and photoluminescence peak of the perovskite nanocrystals can be tuned by varying the concentration of perovskite in the matrix material. The physical origin of the blue shift of the perovskite nanocrystals’ emission compared to its bulk phase is also discussed.

Published
2015

36. Highly Efficient Perovskite Nanocrystal Light-Emitting Diodes Enabled by a Universal Crosslinking Method

Author

Li, Guangru, primary, Rivarola, Florencia Wisnivesky Rocca, additional, Davis, Nathaniel J. L. K., additional, Bai, Sai, additional, Jellicoe, Tom C., additional, de la Peña, Francisco, additional, Hou, Shaocong, additional, Ducati, Caterina, additional, Gao, Feng, additional, Friend, Richard H., additional, Greenham, Neil C., additional, and Tan, Zhi-Kuang, additional

Published
2016
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38. Interfacial Control Toward Efficient and Low‐Voltage Perovskite Light‐Emitting Diodes

Author

Wang, Jianpu, primary, Wang, Nana, additional, Jin, Yizheng, additional, Si, Junjie, additional, Tan, Zhi‐Kuang, additional, Du, Hui, additional, Cheng, Lu, additional, Dai, Xingliang, additional, Bai, Sai, additional, He, Haiping, additional, Ye, Zhizhen, additional, Lai, May Ling, additional, Friend, Richard H., additional, and Huang, Wei, additional

Published
2015
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40. Enhanced Performance in Fluorene‐Free Organometal Halide Perovskite Light‐Emitting Diodes using Tunable, Low Electron Affinity Oxide Electron Injectors

Author

Hoye, Robert L. Z., primary, Chua, Matthew R., additional, Musselman, Kevin P., additional, Li, Guangru, additional, Lai, May‐Ling, additional, Tan, Zhi‐Kuang, additional, Greenham, Neil C., additional, MacManus‐Driscoll, Judith L., additional, Friend, Richard H., additional, and Credgington, Dan, additional

Published
2015
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42. Bright light-emitting diodes based on organometal halide perovskite

Author

Tan, Zhi-Kuang, primary, Moghaddam, Reza Saberi, additional, Lai, May Ling, additional, Docampo, Pablo, additional, Higler, Ruben, additional, Deschler, Felix, additional, Price, Michael, additional, Sadhanala, Aditya, additional, Pazos, Luis M., additional, Credgington, Dan, additional, Hanusch, Fabian, additional, Bein, Thomas, additional, Snaith, Henry J., additional, and Friend, Richard H., additional

Published
2014
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43. In‐Situ Switching from Barrier‐Limited to Ohmic Anodes for Efficient Organic Optoelectronics

Author

Tan, Zhi‐Kuang, primary, Vaynzof, Yana, additional, Credgington, Dan, additional, Li, Cheng, additional, Casford, Mike T. L., additional, Sepe, Alessandro, additional, Huettner, Sven, additional, Nikolka, Mark, additional, Paulus, Fabian, additional, Yang, Le, additional, Sirringhaus, Henning, additional, Greenham, Neil C., additional, and Friend, Richard H., additional

Published
2014
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44. Structure formation in P3HT/F8TBT blends

Author

Sepe, Alessandro, primary, Rong, Zhuxia, additional, Sommer, Michael, additional, Vaynzof, Yana, additional, Sheng, Xiaoyuan, additional, Müller-Buschbaum, Peter, additional, Smilgies, Detlef-M., additional, Tan, Zhi-Kuang, additional, Yang, Le, additional, Friend, Richard H., additional, Steiner, Ullrich, additional, and Hüttner, Sven, additional

Published
2014
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45. Photo-induced thiol coupling and C–H activation using nanocrystalline lead-halide perovskite catalystsElectronic supplementary information (ESI) available: Detailed experimental procedures, spectral data for all compounds, time tracking studies, light “On-Off” study, reusability tests, quantum yield determination, H2detection, and proposed mechanisms. See DOI: 10.1039/c8cy01240g

Author

WuThese authors contributed equally to this work., Wen-Bin, Wong, Ying-Chieh, Tan, Zhi-Kuang, and Wu, Jie

Abstract

The use of photon energy to promote chemical transformations offers versatile control of reaction kinetics and progress. Over the past decade, many photoactive transition-metal complexes and organic chromophores were developed to catalyze chemical transformations, enabling a myriad of reactions and compounds that were previously inaccessible viatraditional synthetic methods. Here, we demonstrate the photocatalytic oxidative coupling of organic thiols using cesium lead halide perovskite nanocrystals as photocatalysts. The photo-catalyzed thiol coupling reactions selectively produced symmetric and unsymmetrical disulfides in high yields (68–96% isolated yields). Additionally, we discovered a perovskite-catalyzed phosphonylation of tertiary amines viavisible-light-mediated cross-dehydrogenative coupling reaction, and obtained good isolated yields (50–96%). The variety of visible-light-induced photocatalytic processes that perovskite nanocrystals are capable of, coupled with their facile preparation, easily tunable redox potentials, high catalytic efficiency and reusability, presents great opportunities for their future applications in green and sustainable organic synthesis.

Published
2018
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47. Efficient Near‐Infrared Light‐Emitting Diodes based on In(Zn)As–In(Zn)P–GaP–ZnS Quantum Dots.

Author

Wijaya, Hadhi, Darwan, Daryl, Zhao, Xiaofei, Ong, Evon Woan Yuann, Lim, Kang Rui Garrick, Wang, Tian, Lim, Li Jun, Khoo, Khoong Hong, and Tan, Zhi‐Kuang

Subjects
QUANTUM dots, QUANTUM dot synthesis, SEMICONDUCTOR nanocrystals, DIODES, ELECTRONIC equipment, ELECTROLUMINESCENCE, QUANTUM efficiency
Abstract

Near‐infrared (NIR) lighting plays an increasingly important role in new facial recognition technologies and eye‐tracking devices, where covert and nonvisible illumination is needed. In particular, mobile or wearable gadgets that employ these technologies require electronic lighting components with ultrathin and flexible form factors that are currently unfulfilled by conventional GaAs‐based diodes. Colloidal quantum dots (QDs) and emerging perovskite light‐emitting diodes (LEDs) may fill this gap, but generally employ restricted heavy metals such as cadmium or lead. Here, a new NIR‐emitting diode based on heavy‐metal‐free In(Zn)As–In(Zn)P–GaP–ZnS quantum dots is reported. The quantum dots are prepared with a giant shell structure, enabled by a continuous injection synthesis approach, and display intense photoluminescence at 850 nm with a high quantum efficiency of 75%. A postsynthetic ligand exchange to a shorter‐chain 1‐mercapto‐6‐hexanol (MCH) affords the QDs with processability in polar solvents as well as an enhanced charge‐transport performance in electronic devices. Using solution‐processing methods, an ITO/ZnO/PEIE/QD/Poly‐TPD/MoO3/Al electroluminescent device is fabricated and a high external quantum efficiency of 4.6% and a maximum radiance of 8.2 W sr−1 m−2 are achieved. This represents a significant leap in performance for NIR devices employing a colloidal III–V semiconductor QD system, and may find significant applications in emerging consumer electronic products. [ABSTRACT FROM AUTHOR]

Published
2020
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48. Thermodynamic Control in the Synthesis of Quantum-Confined Blue-Emitting CsPbBr 3 Perovskite Nanostrips.

Author

Leng J, Wang T, Zhao X, Ong EWY, Zhu B, Ng JA, Wong YC, Khoo KH, Tamada K, and Tan ZK

Abstract

Size control is critical in the synthesis of quantum-confined semiconductor nanocrystals, otherwise known as quantum dots. The achievement of size-uniformity and narrow spectral line-width in quantum dots conventionally relies on a very precise kinetic control of the reactions, where reaction time plays a significant role in defining the final crystal sizes and distribution. Here, we show that synthesis of quantum-confined perovskite nanostrips could be achieved through a thermodynamically controlled reaction, using a low-temperature and ligand-rich approach. The nanostrip growth proceeds through an initial one-dimensional (1D) nanorod stage, followed by the lateral widening of the rod to form a two-dimensional (2D) nanostrip. The spectral characteristics of the final product remain unchanged after prolonged reaction, indicating no signs of crystal ripening and confirming the thermodynamic nature of this reaction. The CsPbBr 3 perovskite nanostrips were highly uniform and emit at a deep-blue wavelength of 462 nm with a remarkably narrow line-width of 13 nm. This corresponds to color coordinates of (0.136, 0.049) on the CIE 1931 color space, which fulfils the stringent Rec. 2020 standard for next-generation color displays. The well-passivated nanostrips also possess negligible defects and provide a near-unity photoluminescence quantum yield at 94%. Crucially, the achievement of blue emission through a pure-halide perovskite circumvents the problems of spectral instability that are frequently experienced in mixed-halide perovskite systems. The convenience and scalability of our thermodynamic approach, coupled with the excellent optical attributes, would likely enable these quantum-confined perovskite systems to be the preferred method toward color control in trichromatic display applications.

Published
2020
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