ORCID Profile
0000-0001-6417-7815
Current Organisations
King Abdullah University of Science and Technology
,
Australian National University
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Publisher: Elsevier BV
Date: 2015
Publisher: American Chemical Society (ACS)
Date: 11-03-2014
DOI: 10.1021/NL500359E
Abstract: Photoelectrochemical (PEC) solar water splitting represents a clean and sustainable approach for hydrogen (H2) production and substantial research are being performed to improve the conversion efficiency. Hematite (α-Fe2O3) is considered as a promising candidate for PEC water splitting due to its chemical stability, appropriate band structure, and abundance. However, PEC performance based on hematite is hindered by the short hole diffusion length that put a constraint on the active layer thickness and its light absorption capability. In this work, we have designed and fabricated novel PEC device structure with ultrathin hematite film deposited on three-dimensional nanophotonic structure. In this fashion, the nanophotonic structures can largely improve the light absorption in the ultrathin active materials. In addition, they also provide large surface area to accommodate the slow surface water oxidation process. As the result, high current density of 3.05 mA cm(-2) at 1.23 V with respect to the reversible hydrogen electrode (RHE) has been achieved on such nanophotonic structure, which is about three times of that for a planar photoelectrode. More importantly, our systematic analysis with experiments and modeling revealed that the design of high performance PEC devices needs to consider not only total optical absorption, but also the absorption profile in the active material, in addition to electrode surface area and carrier collection.
Publisher: IEEE
Date: 06-2015
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C5TA01960E
Abstract: An ultra-thin freestanding Au NSP film is fabricated by simple wet etching. Supercapacitors fabricated based on such structure show notable electrochemical improvements.
Publisher: Royal Society of Chemistry (RSC)
Date: 2014
DOI: 10.1039/C4EE01850H
Abstract: Optimized nanospiked solar cell achieved efficiency of 7.92 % which is among the highest on a flexible substrate.
Publisher: Elsevier BV
Date: 2012
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C8NR01968A
Abstract: In this work, a low-cost, scalable and highly repeatable approach was developed to prepare polystyrene films with three-dimensional nanopyramids on the surface for antibacterial applications.
Publisher: American Chemical Society (ACS)
Date: 18-09-2014
DOI: 10.1021/JP507800T
Publisher: Elsevier BV
Date: 2016
Publisher: Wiley
Date: 18-11-2013
Publisher: Wiley
Date: 25-02-2016
Abstract: Integrating devices with nanostructures is considered a promising strategy to improve the performance of solar energy harvesting devices such as photovoltaic (PV) devices and photo-electrochemical (PEC) solar water splitting devices. Extensive efforts have been exerted to improve the power conversion efficiencies (PCE) of such devices by utilizing novel nanostructures to revolutionize device structural designs. The thicknesses of light absorber and material consumption can be substantially reduced because of light trapping with nanostructures. Meanwhile, the utilization of nanostructures can also result in more effective carrier collection by shortening the photogenerated carrier collection path length. Nevertheless, performance optimization of nanostructured solar energy harvesting devices requires a rational design of various aspects of the nanostructures, such as their shape, aspect ratio, periodicity, etc. Without this, the utilization of nanostructures can lead to compromised device performance as the incorporation of these structures can result in defects and additional carrier recombination. The design guidelines of solar energy harvesting devices are summarized, including thin film non-uniformity on nanostructures, surface recombination, parasitic absorption, and the importance of uniform distribution of photo-generated carriers. A systematic view of the design concerns will assist better understanding of device physics and benefit the fabrication of high performance devices in the future.
Publisher: IEEE
Date: 04-2015
Publisher: Springer Science and Business Media LLC
Date: 07-03-2014
DOI: 10.1038/SREP04243
Publisher: American Chemical Society (ACS)
Date: 08-04-2014
DOI: 10.1021/JZ500306F
Abstract: Light management is of paramount importance to improve the performance of optoelectronic devices including photodetectors, solar cells, and light-emitting diodes. Extensive studies have shown that the efficiency of these optoelectronic devices largely depends on the device structural design. In the case of solar cells, three-dimensional (3-D) nanostructures can remarkably improve device energy conversion efficiency via various light-trapping mechanisms, and a number of nanostructures were fabricated and exhibited tremendous potential for highly efficient photovoltaics. Meanwhile, these optical absorption enhancement schemes can benefit photodetectors by achieving higher quantum efficiency and photon extraction efficiency. On the other hand, low extraction efficiency of a photon from the emissive layer to outside often puts a constraint on the external quantum efficiency (EQE) of LEDs. In this regard, different designs of device configuration based on nanostructured materials such as nanoparticles and nanotextures were developed to improve the out-coupling efficiency of photons in LEDs under various frameworks such as waveguides, plasmonic theory, and so forth. In this Perspective, we aim to provide a comprehensive review of the recent progress of research on various light management nanostructures and their potency to improve performance of optoelectronic devices including photodetectors, solar cells, and LEDs.
Publisher: American Chemical Society (ACS)
Date: 19-02-2013
DOI: 10.1021/NN400160N
Abstract: Efficient light absorption in thin-film photovoltaic (PV) devices is crucial for improving their efficiency and reducing cost. Here we have not only developed a low-cost and scalable method to fabricate a unique type of integrated-nanopillar-nanowell (i-NPW) structure by integrating nanopillar and nanowell arrays together vertically, but also demonstrated the attractive optical property of the i-NPW arrays by leveraging the advantages of "positive" and "negative" nanostructures for photon harvesting. Impressively, the 2 μm thick i-NPW arrays with only 40 nm a-Si coating obtained a day-integrated absorption of 89.27%, as opposed to only 33.45% for the planar control s le. These results suggest the feasibility and clear advantage of vertical integration of three-dimensional (3-D) nanophotonic structures, and meanwhile also pave a viable and convenient way toward a 3-D ultrathin film PV module with potency for high energy conversion efficiency.
Publisher: Wiley
Date: 10-01-2018
Abstract: Flexible and self-powered photodetectors (PDs) are highly desirable for applications in image sensing, smart building, and optical communications. In this paper, a self-powered and flexible PD based on the methylammonium lead iodide (CH
Publisher: Wiley
Date: 10-2018
Abstract: Despite the remarkable progress of optoelectronic devices based on hybrid perovskites, there are significant drawbacks, which have largely hindered their development as an alternative of silicon. For instance, hybrid perovskites are well-known to suffer from moisture instability which leads to surface degradation. Nonetheless, the dependence of the surface effect on the moisture stability and optoelectronic properties of hybrid perovskites has not been fully investigated. In this work, the influence of the surface effect of 2D layered perovskites before and after mechanical exfoliation, representing rough and smooth surfaces of perovskite crystals, are studied. It is found that the smooth 2D perovskite is less sensitive to ambient moisture and exhibits a considerably low dark current, which outperforms the rough perovskites by 23.6 times in terms of photodetectivity. The superior moisture stability of the smooth perovskites over the rough perovskites is demonstrated. Additionally, ethanolamine is employed as an organic linker of the 2D layered perovskite, which further improves the moisture stability. This work reveals the strong dependence of the surface conditions of 2D hybrid perovskite crystals on their moisture stability and optoelectronic properties, which are of utmost importance to the design of practical optoelectronic devices based on hybrid perovskite crystals.
Publisher: Elsevier BV
Date: 03-2017
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/C9EE03566D
Abstract: Sequestering CO 2 in the form of carbon-based liquid fuels would provide both a convenient and sustainable form of energy for practical use as well as mitigate the effects of global warming and climate change.
Publisher: Wiley
Date: 05-2016
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 08-2017
Publisher: American Chemical Society (ACS)
Date: 05-06-2014
DOI: 10.1021/NN5023878
Abstract: Thin film photovoltaic (PV) technologies are highly attractive for low-cost solar energy conversion and possess a wide range of potential applications from building-integrated PV generation to portable power sources. Inverted nanocones (i-cones) have been demonstrated as a promising structure for practical thin film PV devices/modules, owning to their antireflection effect, self-cleaning function, superior mechanical robustness, and so forth. In this work, we have demonstrated a low-cost and scalable approach to achieve perfectly ordered i-cone arrays. Thereafter, thin film amorphous silicon (a-Si:H) solar cells have been fabricated based on various i-cone substrates with different aspect ratios and pitches to investigate the impact of geometry of i-cone nanostructures on the performance of the as-obtained PV devices. Intriguingly, the optical property investigations and device performance characterizations demonstrated that the 0.5-aspect-ratio i-cone-based device performed the best on both light absorption capability and energy conversion efficiency, which is 34% higher than that of the flat counterpart. Moreover, the i-cone-based device enhanced the light absorption and device performance over the flat reference device omnidirectionally. These results demonstrate a viable and convenient route toward scalable fabrication of nanostructures for high-performance thin film PV devices based on a broad range of materials.
Publisher: Wiley
Date: 09-2008
Publisher: IEEE
Date: 04-2014
Publisher: Royal Society of Chemistry (RSC)
Date: 2014
DOI: 10.1039/C3NR06675D
Abstract: 3D electrodes are critical to high-performance power sources. Now by combining imprint and soft-printing technologies, 3D nanocone arrays have been designed and fabricated for high performance pseudocapacitors.
Publisher: Elsevier BV
Date: 04-2019
Publisher: Elsevier BV
Date: 11-2019
Publisher: American Chemical Society (ACS)
Date: 25-04-2018
Abstract: Piezoelectric materials have been widely used for sensors, actuators, electronics, and energy conversion. Two-dimensional (2D) ultrathin semiconductors, such as monolayer h-BN and MoS
Publisher: Springer Science and Business Media LLC
Date: 13-02-2019
DOI: 10.1038/S41467-019-08561-Y
Abstract: Metal halide perovskite has emerged as a promising material for light-emitting diodes. In the past, the performance of devices has been improved mainly by optimizing the active and charge injection layers. However, the large refractive index difference among different materials limits the overall light extraction. Herein, we fabricate efficient methylammonium lead bromide light-emitting diodes on nanophotonic substrates with an optimal device external quantum efficiency of 17.5% which is around twice of the record for the planar device based on this material system. Furthermore, optical modelling shows that a high light extraction efficiency of 73.6% can be achieved as a result of a two-step light extraction process involving nanodome light couplers and nanowire optical antennas on the nanophotonic substrate. These results suggest that utilization of nanophotonic structures can be an effective approach to achieve high performance perovskite light-emitting diodes.
Publisher: American Chemical Society (ACS)
Date: 02-12-2016
DOI: 10.1021/ACS.ANALCHEM.6B03170
Abstract: A facile single-cell patterning (ScP) method was developed and integrated with time-of-flight secondary ion mass spectrometry (TOF-SIMS) for the study of drug-induced cellular phenotypic alterations. Micropatterned poly(dimethylsiloxane) (PDMS) stencil film and centrifugation-assisted cell trapping were combined for the preparation of on-surface single-cell microarrays, which exhibited both high site occupancy (>90%) and single-cell resolution (>97%). TOF-SIMS is a surface-sensitive mass spectrometry and is increasingly utilized in biological studies. Here we demonstrated, for the first time, its successful application in high-throughput single-cell analysis. Drug-induced phenotypic alterations of HeLa cells in the early stage of apoptosis were investigated using TOF-SIMS. The major molecular sources of variations were analyzed by principle component analysis (PCA).
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3EE41139G
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C5NR08836D
Abstract: Utilization of nanostructures on photovoltaic devices can significantly improve the device energy conversion efficiency by enhancing the device light harvesting capability as well as carrier collection efficiency. However, improvements in device mechanical robustness and reliability, particularly for flexible devices, have rarely been reported with in-depth understanding. In this work, we fabricated efficient, flexible and mechanically robust organometallic perovskite solar cells on plastic substrates with inverted nanocone (i-cone) structures. Compared with the reference cell that was fabricated on a flat substrate, it was shown that the device power conversion efficiency could be improved by 37%, and reached up to 11.29% on i-cone substrates. More interestingly, it was discovered that the performance of an i-cone device remained more than 90% of the initial value even after 200 mechanical bending cycles, which is remarkably better than for the flat reference device, which degraded down to only 60% in the same test. Our experiments, coupled with mechanical simulation, demonstrated that a nanostructured template can greatly help in relaxing stress and strain upon device bending, which suppresses crack nucleation in different layers of a perovskite solar cell. This essentially leads to much improved device reliability and robustness and will have significant impact on practical applications.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2019
Publisher: Springer Science and Business Media LLC
Date: 07-06-2013
Abstract: Porous anodic alumina membranes (AAMs) have attracted great amount of attention due to their potential application as templates for nanoengineering. Template-guided fabrication and assembly of nanomaterials based on AAMs are cost-effective and scalable methods to program and engineer the shape and morphology of nanostructures and nanomaterials. In this work, perfectly ordered AAMs with the record large pitch up to 3 μm have been fabricated by properly controlling the anodization conditions and utilization of nanoimprint technique. Due to the capability of programmable structural design and fabrication, a variety of nanostructures, including nanopillar arrays, nanotower arrays, and nanocone arrays, have been successfully fabricated using nanoengineered AAM templates. Particularly, amorphous Si nanocones have been fabricated as three-dimensional nanophotonic structures with the characterization of their intriguing optical anti-reflection property. These results directly indicate the potential application of the reported approach for photonics and optoelectronics.
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3EE90047A
Location: Saudi Arabia
No related grants have been discovered for Siu-Fung Leung.