All-inorganic perovskite CsPbBr3 has emerged as a promising candidate for stable and cost-effective photovoltaic applications. Pulsed laser deposition (PLD), as a solvent-free, material-efficient, and highly controllable thin-film growth technique, holds tremendous promise for the fabrication of photovoltaic devices. However, during the deposition process, the loose structure, poor thermal conductivity, and microstructural defects of conventional CsPbBr3 targets give rise to the generation of large neutral particles in the ablation plume, deteriorating film quality, and consequently limit device performance. In this work, these bottlenecks are addressed by introducing melt-quenched CsPbBr3 targets to replace conventional powder-pressed ones. Comprehensive analyses reveal that the emission of large neutral particles from the melt-quenched targets and the kinetic energy of species in the ablation plume are both suppressed during deposition, which mitigates the formation of deep-level defects, improves the quality of the thin films, and precludes band misalignment caused by surface dipoles. Ultimately, perovskite solar cells (PSCs) fabricated with the aforementioned target engineering achieve a maximum power conversion efficiency (PCE) of 10.71% and retaining a 93% of initial PCE over 150 days under ambient conditions without any encapsulation. This work presenting a compelling route toward large-area, inline manufacturing and large-scale commercialization for CsPbBr3 PSCs.

Mechanical systems with moving parts and/or fluids, such as heat exchangers and turbomachinery, often experience vibration. Furthermore, these systems often benefit from effective water droplet removal to improve air-side heat transfer, avoid corrosion pitting of turbine blades, etc. Therefore, designing these systems requires a deeper understanding of a droplet's vibrational response on the surface of interest. In addition to uniform surfaces, topographic wetting gradients are also examined due to their ability to promote the spontaneous motion of water droplets on a surface for directional control. Topographic wetting gradients, produced in a one-step industrial process, have the potential to enhance heat exchanger performance, promote dropwise vs filmwise condensation, and facilitate more complete water drainage. This is enabled by net surface tension forces across the gradient, which drive droplet motion, especially when coupled with vibration. More specifically, we study the droplet behavior influenced by both vertical and horizontal vibration on polished and superhydrophobic coated aluminum surfaces as well as on uncoated aluminum surfaces containing variable-pitch micro/nanoengineered topographic wetting gradients. These experiments demonstrated a nonlinear response in the droplet behavior depending on the test surface and the combinations of forced vibration amplitude and frequency that were used to create the droplet lateral motion, which in some cases was up to 6.5 mm for droplet volumes of 5 and 10 mu l. The range of examined frequencies was 20-200 Hz since these frequencies were observed on operating heat exchangers, whereas the range of displacements (i.e., amplitudes) was 50-2000 mu m, which expands all previously reported data. (c) 2025 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC) license (https://creativecommons.org/licenses/by-nc/4.0/). https://doi.org/10.1063/5.0280311

Lithium tetraborate (LB4) is a nonlinear crystal that has very low optical absorption in the visible and ultraviolet range. Hence, it is a very interesting material for nonlinear conversion experiments, particularly in whispering gallery mode (WGM) resonators. Here, we show theoretically that second-harmonic generation is possible over a wide range of pump wavelengths ( to ) in an 488nm-cut LB4 WGM resonator. We also demonstrate this experimentally at three different pump wavelengths (, , and ). We find a reasonable conversion efficiency of for the generation of UV light at . This is possible due to the high-quality factors on the order of and the use of the so-called selective coupling method.

Lowering the population inversion threshold is key to leveraging quantum dots (QDs) for nanoscale lasing and laser miniaturization. However, optical realization of population inversion in QDs has an inherent limitation: the number of excited electrons per QD is bound by the absorbed photons. Here we show that one can break this population limit and realize near-zero threshold inversion via plasmonic doping. Specifically, we integrate QDs into a grating-like plasmonic resonator, which, upon optical excitation, can transiently dope the QDs with numerous highly energetic electrons and make excited electrons in the QDs outnumber absorbed photons. This high population under low excitation blocks QD absorption and reduces the population-inversion threshold over 100 times compared to neutrally populated QDs. Our findings not only reveal new understanding of cavity-emitter interactions but also provide practical avenues for zero-threshold lasing, nanolasing and amplification devices.

Drop impact phenomena on raw, polished, and topography-altered gradient surfaces are investigated and presented. The main aim of this study is to demonstrate that in using a one-step industrial patterning process, it is possible to obtain metal topographical wetting gradients that can produce various desired outcomes after droplet impact. The findings could be applied to improving wind or steam turbine blades. The ranges of Weber (We) and Reynolds (Re) numbers in the study are 3-300 and 650-6500, respectively. It is demonstrated that for a fixed We, the droplet transport outcomes change from bouncing-off to side-flipping to deposition depending on the impact location and the gradient strength. The effect of We in combination with the gradient strength was also considered to demonstrate droplet behavior similar to that observed on a uniform water repellent surface and on biphilic systems. In addition, full bouncing-off and directional control have been demonstrated. For the condition We = 95 ± 3, it was possible to achieve a maximum droplet recoil height of ∼6 mm and a side motion of almost 8 mm. A combination of different outcomes (e.g., splashing on one side of a droplet and passive horizontal translation on another) was observed on the studied gradients at We > 200 due to different wetting regimes across the droplet's three-phase line.

Exciton transport is a fundamental process that underlies the functionality of semiconductor optoelectronicdevices. However, when excitons interact with one another, their transport pattern becomes unpredictable, posinga great challenge to harness their full potential in various applications. In our study, focusing on the excitondensity change in a tungsten-disulfide monolayer, we observed that strong interactions between excitons canactually stop their movement. This finding contradicts the typical understanding of consistent exciton movementand reveals that a higher density might decrease the exciton-exciton annihilation rate due to reduced mobility.Our findings offer a valuable technique to examine exciton transport and deepen our grasp of their behavior inmany-body interactions, which could pave the way for better-performing excitonic devices.

The abrasion testing process of topographically modified surfaces is investigated and their mechanical durability and wear characteristics are presented. The primary aim of the study is to demonstrate that a simple abrasion testing process carries a number of subtle complexities which are crucial for getting comparable results—i.e., sample area, abrasion duration, and presence of a microstructure. All of these factors can significantly alter the results of the testing process and have to be considered during comparison with other durability results. This study also demonstrates how topographically modified aluminum structures tend to restore their hydrophobicity after noticeable mechanical damage due to the natural oxidation process, whereas control samples stay in a hydrophilic state. The findings could be applied to improving the performance of wind or steam turbine blades.

HYPOTHESIS:There is a relationship between the static contact angle of droplets and soap bubbles on flat homogeneous surfaces, therefore, it should be possible to derive a relationship between the static contact angle of a soap bubble on a periodic topographic surface and a droplet on a flat homogeneous surface. EXPERIMENTS:A free energy model of the static contact angle of soap bubbles on a topographic surface in the Cassie-Baxter state was derived. Polydimethylsiloxane surfaces of varying area fraction (0.125, 0.250, 0.500, 0.750, and 1.00) and periodic topographies (lined and pillared) were fabricated using 3D printed moulds for pattern transfer. A bubble goniometer was developed to accommodate bubbles of 40,000 ± 5,000 mm3 and 50,000 ± 5,000 mm3 volumes. Then, the static contact angle of bubbles of both volumes were measured on the varying topographic surfaces. FINDINGS:The derived predictions imply that the relationship between the static contact angle for bubbles on a flat homogeneous surface and on a composite surface, has the same form as the Cassie-Baxter equation for a droplet. The experimental results for the measured static contact angle for both bubble volumes on the varying surfaces had good agreement with the predicted trends.

Photocatalytic water splitting has attracted significant attention as a low-cost, clean, and green method for the conversion of solar energy into hydrogen, highlighting its potential to solve energy and environmental problems. In this work, we report the coupling of a plasmonic resonator with semiconductor quantum dots (QDs) for enhancement in photoelectrocatalytic water splitting toward hydrogen (H2) production. Specifically, cadmium selenide (CdSe) QDs were deposited on silver nano-gratings (Ag gratings). Plasmonic enhancement was observed in the absorption/emission of QDs using our angle-resolved steady-state optical spectroscopy. Furthermore, angle-resolved absorption spectra helped us to optimize the illumination conditions for resonant excitation using a setup for photoelectrochemical (PEC) experiments. Under the resonant pump, the emission of the QDs has been plasmonically enhanced with a Purcell factor (FP) of ∼1.5. Our numerical simulation revealed a strong near-field enhancement due to the excitation of surface plasmon resonances, contributing to FP. A similar enhancement order in the PEC experiments was also observed under resonant pump conditions, indicating the contribution of plasmon resonances to the enhanced photoelectrocatalysis. Switching the excitation's polarization further reinforces this, resulting in an enhanced photocurrent under p-polarization. These findings provide a proof of concept, thus laying the foundation for a practical device for efficient solar-to-H2 conversion.

Plasmonic resonators are widely used for the manipulation of light on subwavelength scales through the near-field electromagnetic wave produced by the collective oscillation of free electrons within metallic systems, well known as the surface plasmon (SP). The non-radiative decay of the surface plasmon can excite a plasmonic hot electron. This review article systematically describes the excitation progress and basic properities of SPs and plasmonic hot electrons according to recent publications. The extraction mechanism of plasmonic hot electrons via Schottky conjunction to an adjacent semiconductor is also illustrated. Also, a calculation model of hot electron density is given, where the efficiency of hot-electron excitation, transport and extraction is discussed. We believe that plasmonic hot electrons have a huge potential in the future development of optoelectronic systems and devices.

Passive gradient motion found in nature is becoming a point of interest for heat exchange and green energy technologies. Surfaces with a topographical gradient could potentially enhance heat exchanger performance, promote dropwise vs filmwise condensation, or delay icing on wind turbines by assisting in the removal of condensed or impacted droplets. Coating-free topographical surface tension gradients can be fabricated via various methods and need to be examined in terms of their capability for spontaneous droplet motion. In this work, a simple experimental method, coupled with numerical modeling and force analysis, for examining variable-pitch micro/nanoengineered hierarchical superhydrophobic gradients is shown. The method was validated against numerical calculations, allowing the strength of the gradients to be compared. In most cases, model predictions for droplet travel distance and velocity were within 20% of the measured data. This method could also be useful for gradient design improvements in the absence of spontaneous motion on a horizontal surface.

A higher detection performance and stability are always pursued in the development of photoelectric or photo-electrochemical devices, critical for their further commercial application. Here, we report a CsPbBr3-based photodetector engineered from a multilayer Si/Ag islands/CsPbBr3/PMMA system, showing an evidently enhanced photosensitization and breaking the absorption edge of CsPbBr3. On the one hand, the photocurrent contribution from plasmonic hot-electron injection effectively extends the detection limit of our photodetectors much below the band edge of CsPbBr3, depending only on Schottky barrier. On the other hand, the surface plasmons on nanoscale silver islands can considerably improve the light harvesting ability of the CsPbBr3 layer, ascribed to the confinement of light in the adjacency of silver islands. Numerical simulations show the localized enhancement of light near silver islands, corresponding to the excitation of localized surface plasmon resonances. It shows a higher light intensity distribution inside the CsPbBr3 layer of the photodetector consisting of Si/Ag islands/CsPbBr3/PMMA with the photodetector with only Ag islands in accordance with their current–voltage(I–V) characteristics. Ultimately, our plasmonic CsPbBr3-based photodetector presents a >10-fold increase in the photocurrent and a doubling of the operating lifetime. Our work provides important insight into the realization of the performance and stability of optoelectronic devices based on plasmonics.

Plasmonic resonators, which can enhance the near-field due to plasmon excitation, have attracted extensive research interest due to their significant potential in photodetection, photocatalysis, photovoltaics, and other applications. Here, we experimentally present spectroscopic results of plasmonic resonances on large-area nanoscale silver (Ag) gratings, fabricated by optical interference lithography based on angle-resolved optical absorption spectroscopy and femtosecond transient absorption spectroscopy (TAS). Specifically, we have measured plasmon resonances as a function of azimuthal angles and detection angles under p- and s-polarization. TAS reveals the non-radiative decay of plasmon resonances by transferring energy to nearby species, including exciting plasmonic hot electrons, which can be harvested by coupled semiconductors through a metal-semiconductor Schottky barrier. Our numerical simulation provides insight into the near-field analysis and quantifies the density of plasmonic hot electrons excited in our Ag-gratings.

In this work, a shear stress test is used to evaluate the ice adhesion strength on “as received”, polished and micro/nanoengineered hierarchical superhydrophobic aluminium (produced via one-step laser etching) with fixed- and gradient-pitch structures. Due to the potential mismatch between the ice formation area and the wetting gradient length scale, the shear stress test method has been analysed in detail to understand its applicability to topographic gradients, since this could provide misleading results as compared with the application of this method to fixed-pitch topographic structured surfaces. To address this, the influence of the ice-surface contact area, as well as the mould shape and mould material, on the ice adhesion results, was observed for all samples. Moreover, the impact of the direction of the removal force was investigated on the wetting gradients. Key results are that topographically altered surfaces can be hydrophobic, but not icephobic; whereas non-altered surfaces are hydrophilic, but with much lower ice adhesion. Additionally, gradient surfaces were observed to provide hydrophobicity for most areas of the surface, while allowing removal of the ice column at lower forces from certain directions.

Passive gradient-driven droplet motion has been demonstrated in nature, inspiring coating-free surface tension gradient surfaces that can be fabricated via laser ablation. These surfaces can potentially enhance heat exchanger performance, promoting drop-wise over film-wise condensation, and be suitable for lab-on-a-chip applications, allowing the directional transport of microliter size droplets. In this work, a theoretical model and its application to variable-pitch hierarchical superhydrophobic gradients are discussed, and the method is experimentally validated against various gradient topographical designs. The proposed force balance model allows analysis of the impact of the topography on the forces acting on the droplet. The discrepancy between modeled and observed contact angles in most cases does not exceed 10%. The modeled droplet footprint fits the experimentally measured ones with an error of less than 10% for most cases. Though modeled motion distances were twice greater than experimentally observed ones, the comparison of the proposed model with the originally developed theory showed that the difference in the net force was less than 5%. Both observed and average velocities were within less than 30% difference. Like the traditional models, the new model overestimates droplet kinematics; however, it does not require knowledge a priori of all the contact angles across the gradient during droplet motion, relying only on the material's surface tension and the local surface area fraction. Therefore, the model presents a simplified and convenient means of designing a linear topographical gradient for spontaneous droplet motion.

Optical resonators can alter quantum emitters' electromagnetic environment, thus modifying the spontaneous emission. This is known as the Purcell effect, widely regarded as the standard explanation of cavity-emitter interations. Here we show that this effect fails to properly address the emission modified by plasmonic resonators, i.e. a special type of metal cavities, where resonators can strongly affect the transition processes by charging the emitters. In particular, by integrating quantum dots (QDs) into a grating-like plasmonic resonator, we can transiently dope the QDs with a large amount of hot electrons that are produced during plasmon excitation. The doping makes the excited carriers greatly outnumber the absorbed photons, forming unusal ``asymmetric excitation" in individual QDs and yielding high-frequency radiative emission that can not be enabled by the Purcell enhancement. Our finding identifies a new cavity-emitter interaction pathway, initiating riveting opportunities for both fundamental studies and practical applications in laser, photovoltaics and photocatalysis.

Effective optical absorption is highly desirable for numerous applications in energy harvesting and optoelectronics. Bifacial absorbers can significantly enhance light absorption by capturing albedo light from the environment. Here, we experimentally demonstrate that free-standing silica-silver core–shell nano-resonator arrays allow bifacial and omnidirectional optical absorption across the visible spectrum. Specifically, resonator arrays can highly absorb light (>80%) with all polarizations from a directional range (−40° to 40°) on both front and rear sides of a surface. Numerical simulations reveal that such bifacial and omnidirectional light absorption results from hybridized excitation of surface plasmons and whispering gallery modes in a symmetrical configuration. The absorption band can be flexibly adjusted by changing the silica core size. In addition, the absorbed optical energy quickly decays as the excitation of plasmonic hot electrons as observed using transient absorption spectroscopy. Our work provides a bifacial absorber for many optoelectronic applications in photodetection, photovoltaics, and photocatalysis.

Hypothesis: Topographic micro-structures can potentially encourage ice removal from a surface, by weakening the ice at the ice-surface interface. Random and periodic structures have both been investigated, however gradient-pitch structures, where the spacing between structures changes, have not been reported. Gradient pitch structures are anisotropic, creating a force imbalance which is expected to aid ice removal compared with flat surfaces and surfaces with isotropic structures. Applying force to the ice from different directions is also expected to affect the adhesion strength. Experiments: Topographic aluminium microlines, with gradient-pitch spacing, are tested for the first time for anti-icing properties, with fixed-pitch structures and smooth aluminium tested as a comparison. Both types of structures, fabricated by micro-milling, are characterised for their geometric and surface wetting properties (static contact angle, contact angle hysteresis and microwetting state) and tested for ice adhesion strength using the force probe technique. Findings: The gradient-pitch surfaces reduce the ice adhesion strength by about 50% compared with baseline control surfaces. The direction from which the force was applied was found to have an effect on the adhesion strength of the ice to the surface, with the lowest ice adhesion strength recorded when force was applied in the direction of the microlines.

The rapid global rise of COVID-19 from late 2019 caught major manufacturers of RT-qPCR reagents by surprise and threw into sharp focus the heavy reliance of molecular diagnostic providers on a handful of reagent suppliers. In addition, lockdown and transport bans, necessarily imposed to contain disease spread, put pressure on global supply lines with freight volumes severely restricted. These issues were acutely felt in New Zealand, an island nation located at the end of most supply lines. This led New Zealand scientists to pose the hypothetical question: in a doomsday scenario where access to COVID-19 RT-qPCR reagents became unavailable, would New Zealand possess the expertise and infrastructure to make its own reagents onshore? In this work we describe a review of New Zealand's COVID-19 test requirements, bring together local experts and resources to make all reagents for the RT-qPCR process, and create a COVID-19 diagnostic assay referred to as HomeBrew (HB) RT-qPCR from onshore synthesized components. This one-step RT-qPCR assay was evaluated using clinical samples and shown to be comparable to a commercial COVID-19 assay. Through this work we show New Zealand has both the expertise and, with sufficient lead time and forward planning, infrastructure capacity to meet reagent supply challenges if they were ever to emerge.

Superhydrophobic surfaces demonstrate extreme water-repellence, promoting drop-wise over film-wise condensation, increasing liquid mobility, and reducing thermal resistance for heat-exchanger applications. Introducing topographic structures can lead to modified surface free energy, as inspired by natural systems like the lotus leaf, potentially allowing coating-free ice- and frost-free surfaces under certain conditions. This work presents a study of coating-free aluminum micro/nanopatterns fabricated using micromilling or laser-etching techniques and the resultant wetting properties. Our review and experiments clarify the roles of line-edge-roughness and microstructural geometry from each microfabrication technique, which manifests in technique-specific nano- to midmicro-scale roughness, producing a hierarchical structure in both cases. For micromilling, line-edge-roughness consists of jagged burrs of 1-8 μm thickness with 10-25 μm periodicity along the microlines with constantly changing height on the order of 1-20 μm. These effects simultaneously raise the water contact angle from 52° (unprocessed aluminum) up to 136° but with strong edge pinning effects. On the other hand, laser-etched surfaces exhibit line-edge-roughness with a microstructure of 3-20 μm width and 5-10 μm in height superimposed with evenly spread spikes of 50-250 nm. This results in a high contact angle (>150°) coupled with a low contact angle hysteresis (<15°), promoting superhydrophobicity on a coating-free aluminum surface. It is also shown that for certain cases, line-edge-roughness is more important for the resultant wetting properties than the structure geometry.