A5042870297- Quantum Dots Synthesis And Properties
- Chalcogenide Semiconductor Thin Films
- Conducting polymers and applications
- Perovskite Materials and Applications
- Nanomaterials and Printing Technologies
- Gold and Silver Nanoparticles Synthesis and Applications
- Plasmonic and Surface Plasmon Research
- Nanofabrication and Lithography Techniques
- Copper-based nanomaterials and applications
- Nanocluster Synthesis and Applications
- Semiconductor materials and interfaces
- Graphene research and applications
- Thin-Film Transistor Technologies
- Photonic Crystals and Applications
- Gas Sensing Nanomaterials and Sensors
- Advanced Sensor and Energy Harvesting Materials
- Organic Electronics and Photovoltaics
- Carbon and Quantum Dots Applications
- Carbon Nanotubes in Composites
- Force Microscopy Techniques and Applications
- Liquid Crystal Research Advancements
- Advanced Fiber Laser Technologies
- Laser-Ablation Synthesis of Nanoparticles
- Supercapacitor Materials and Fabrication
- Advancements in Photolithography Techniques
University of Oxford
2013-2024
The University of Queensland
2000-2004
Princess Alexandra Hospital
2000
Cation-exchange has been used to synthesize PbS/CdS core/shell colloidal quantum dots from PbS starting cores. These were then incorporated as the active material in solar cell test devices using a solution-based, air-ambient, layer-by-layer spin coating process. We show that can replace their unshelled counterparts with similar band gap layer device, leading an improvement open circuit voltage 0.42 0.66 V. This is attributed reduction recombination result of passivating shell. However, this...
Perovskite quantum dots (PQDs) emerged as a promising class of material for applications in lighting devices, including light emitting diodes and lasers. In this work, we explore nonlinear absorption properties PQDs showing the spectral signatures size dependence their two-photon (2PA) cross-section, which can reach values higher than 106 GM. The large 2PA cross section allows low threshold induced amplified spontaneous emission (ASE), be 1.6 mJ/cm2. We also show that ASE are strongly...
Hybrid colloidal quantum dot (CQD) solar cells are fabricated from multilayer stacks of lead sulfide (PbS) CQD and single layer graphene (SG). The inclusion interlayers is shown to increase power conversion efficiency by 9.18%. It that the conductive enhances charge extraction in devices. Photoluminescence shows quenches emission suggesting spontaneous transfer graphene. photodetectors exhibit increased photoresponse improved transport properties. We propose CQD/SG hybrid structure a route...
We demonstrate the tunable enhancement of zero phonon line a single nitrogen-vacancy color center in diamond at cryogenic temperature. An open cavity fabricated using focused ion beam milling provides mode volumes as small 1.24 $\mu$m$^3$. In-situ tuning resonance is achieved with piezoelectric actuators. At optimal coupling full signal from individual transitions enhanced by about factor 10 and overall emission rate NV$^-$ increased 40% compared that measured same absence field confinement....
The ability of individual nanocube patch antennas, consisting a silver separated from an Ag sheet by thin fluoropolymer spacer, to act as subwavelength sensing elements is demonstrated. An increase in relative humidity (RH) causes the spacer expand, which alters resonance plasmon cavity mode formed between cube and sheet. Using bottom‐up fabrication techniques, sensitivities up 0.57 nm/% RH are recorded, resolution better than 1% achieved with rapid response time, making this most effective...
Lead sulfide colloidal quantum dot (CQD) solar cells demonstrate extremely high short-circuit currents (Jsc) and are making decent progress in power conversion efficiencies. However, the low fill factors (FF) open-circuit voltages have to be addressed with urgency prevent stalling of efficiency improvements. This paper highlights importance improving hole extraction, which received much less attention as compared electron-accepting component device architecture (e.g., TiO2 or ZnO). Here, we...
The application of indium-free quaternary chalcogenides, such as Cu2ZnSnS4 (CZTS), in photovoltaics has created tremendous interest recent years. In this paper we develop a method to synthesize high quality CZTS nanoparticles with thermodynamically stable kesterite and wurtzite phases via simple, one-pot, low-cost solution method.
The effect of a thin dielectric film on the plasmonic behaviour metal nanoparticles (MNPs) above high refractive index substrate is explored. Using finite-difference time domain simulations, optical properties Ag are investigated as function thickness, index, and particle position within film. We demonstrate that addition around MNP at air interface high-index substrate, where nair<nfilm<nsubstrate, will always increase fraction light coupled to (Fsubs). It found placement...
The band structure of colloidal quantum dot (CQD) bilayer heterojunction solar cells is optimized using a combination ligand modification and QD gap control. Solar with power conversion efficiencies up to 9.33 ± 0.50% are demonstrated by aligning the absorber hole transport layers (HTL). Key achieving high optimizing relative position both valence Fermi energy at CQD interface. By comparing different CQDs ligands, we find that smaller HTL in more p-type-inducing found enhance extraction...
Achieving control of the surface chemistry colloidal quantum dots (CQDs) is essential to fully exploit their properties in solar cells, but direct measurement and electronic structure outermost atomic layers challenging. Here we probe oxidation passivation cation-exchanged PbS/CdS core/shell CQDs with sub nm-scale precision using synchrotron-radiation-excited depth-profiling photoemission. We investigate composition topmost 1–2.5 nm as a function depth, for varying CdS shell thickness,...
Solution processable metallic nanomaterials present a convenient way to fabricate conductive structures, which are necessary in all electronic devices. However, they tend require post-treatments remove the bulky ligands around them achieve high conductivity. In this work, we method formulate post-treatment free silver nanowire ink by controlling type of nanowires. We found that bidentate with rigid molecular structure were effective improving conductivity networks as could maximize number...
Time-resolved laser-pump X-ray-photoemission-probe spectroscopy of a ZnO (101¯0) substrate with and without PbS quantum dots (QDs) chemically linked to the surface is performed, using laser photon energies resonant below band gap energy (λ = 372 640 nm, hν 3.33 1.94 eV). Charge injection from photoexcited QDs demonstrated through change in photovoltage observed when heterojunction illuminated eV radiation. The measured carrier dynamics are limited by persistent photoconductivity ZnO, giving...
Transfer-printed silver nanowire transparent conducting electrodes are demonstrated in lead sulfide–zinc oxide quantum dot solar cells. Advantages of using this conductor technology increased junction surface energy, solution processing, and the potential cost reduction low temperature processing. Joule heating, device aging, film thickness effects investigated to understand shunt pathways created by nanowires protruding perpendicular film. A Voc 0.39 ± 0.07 V, Jsc 16.2 0.2 mA/cm2, power...
Bulk heterojunction solar cells made by vacuum co-evaporation of polythiophene (PTh) and fullerene (C60) are reported the blend morphology control through donor-acceptor composition post-situ annealing demonstrated. Co-deposited heterojunctions shown to generate about 60% higher photocurrents than their thickness-optimized PTh/C60 planar counterparts. Furthermore, devices power conversion efficiency is improved as much 80%. UV-vis, XRD AFM analysis shows that enhanced photoresponse a result...
The performance of devices containing colloidal quantum dot (CQD) films is strongly dependent on the surface chemistry CQDs they contain. Multistep treatments, which combine two or more strategies, are important for creating with high carrier mobility that well passivated against trap states and oxidation. Here, we examine effect a number these treatments PbS CQD films, including cation exchange to form PbS/CdS core/shell CQDs, solid-state ligand-exchange Cl, Br, I, 1,2-ethanedithiol (EDT)...
Pressure sensing is an important aspect of many processes and has a wide range applications such as robotics health monitoring. With the shift toward flexible wearable technology, it essential to develop high-performance pressure sensors. In this study, we use solvodynamic printing fabricate highly conductive piezoresistive composite films consisting silver nanowires embedded in ethylene-co-vinyl acetate matrix. The performance sensor tunable based on composition patterning film. can operate...
Polystyrene spheres are used to template TiO2 with a single layer of 300 nm wells which infilled PbS quantum dots form heterojunction solar cell. The porous well device has an efficiency 5.7% while the simple planar junction is limited 3.2%. Using combination optical absorption and photocurrent transient decay measurement we determined that performance enhancement comes from enhanced increased carrier lifetime.
The effective utilization of graphene in optoelectronic devices requires blending with other semiconductor materials, such as lead chalcogenide nanocrystals, and an understanding the organic–inorganic interface at atomic level. In this paper, we present first report successful self-assembly close-packed monolayer arrays PbTe nanocrystals on graphene. By using ultraclean chemical vapor deposition grown aberration corrected transmission electron microscopy unambiguous delineation a ∼2 nm soft...
PbTe nanocrystals were deposited onto the surface of graphene and used as a reservoir Pb Te atoms. Electron beam irradiation at 80 kV caused atoms to mobilize disperse across graphene. We studied dynamics these in real time using aberration-corrected transmission electron microscopy. The found attach layer amorphous carbon that resides upon graphene, well its edge. not residing on pristine but bond free edge states along hole edges. Small nanoclusters tended only form regions
We present a method to directly align PbS nanocrystals in micron-sized superstructures within conjugated polymer. First, lead sulfide are synthesized MEH-PPV suspension via single pot, surfactant-free method. Post-synthesis precipitation of the composite solution involving mild oxidation results formation nanocrystal–polymer and nanocrystal-oxide superstructures. Detailed TEM is used study crystallographic nature these structures roles polymer sulfate. An epitaxial relationship between...
Abstract Printing techniques are becoming increasingly prevalent in modern manufacturing. However, its biggest drawback is the limit printing resolution. In this paper, we present solvodynamic as a novel system which aims to improve print resolution by incorporating an additional immiscible carrier solvent into ink delivery system. The improved due solvent-solvent interactions between and alter contact angle of on substrate printed feature size. We demonstrate proof concept silver...
The effect of a low refractive index film on plasmonic scattering from individual silver nanoparticles and nanowires is observed experimentally in Fourier space. addition the over particles glass substrate was found to have strong pattern, due interference between directly scattered light reflected interfaces, which depends strongly thickness. Nanowires are shown produce much more directional pattern than spherical particles, above leads further directionality enhancements with at...
Multi-band gap heterojunction solar cells fabricated from a blend of 1.2 eV and 1.4 PbS colloidal quantum dots (CQDs) show poor device performance due to non-radiative recombination. To overcome this, CdS shell is epitaxially formed around the core using cation exchange. From steady state transient photoluminescence measurements, we understand nature charge transfer between these dots. Photoluminescence decay lifetimes are much longer in PbS/CdS core/shell compared only, explained by...