Effective photon management is critical to realize high power conversion efficiencies for thin crystalline silicon (c‐Si) solar cells. Standard few‐100‐µm‐thick bulk cells achieve light trapping with ...macroscopic surface textures covered by thin, continuous antireflection coatings. Such sizeable textures are challenging to implement on ultrathin cells. Here, it is illustrated how nanoscale Mie‐resonator‐arrays with a bimodal size distribution support multiple resonances that can work in concert to achieve simultaneous antireflection and light‐trapping across the broad solar spectrum. The effectiveness of these light‐trapping antireflection coatings is experimentally demonstrated on a 2.8 µm‐thick c‐Si solar cell. The measured short‐circuit current and corresponding power conversion efficiency are notably improved, achieving efficiencies as high as 11.2%. Measurements of the saturation current density on completed cells indicate that thermal oxides can effectively limit surface recombination. The presented design principles are applicable to a wide range of solar cells.
A nanophotonic design strategy to realize Mie‐resonator arrays that can combine antireflection and light‐trapping functions in a single, thin layer is discussed. The proposed light‐trapping antireflection coating is experimentally demonstrated on a 2.8 µm‐thick crystalline silicon (c‐Si) solar cell, resulting in a 48% enhancement in the short‐circuit current as compared to a planar cell and an absolute efficiency of 11.2%.
Thin, flexible, and efficient silicon solar cells would revolutionize the photovoltaic market and open up new opportunities for PV integration. However, as an indirect semiconductor, silicon exhibits ...weak absorption for infrared photons and the efficient absorption of the full above bandgap solar spectrum requires careful photon management. This review paper provides an overview on the fundamental physics of light trapping and explains known theoretical limits. Technologies that have been developed to improve light trapping will be discussed, and limitations will be addressed.
Thin, flexible, and efficient silicon solar cells would revolutionize the photovoltaic market and open up new opportunities for PV integration. However, as an indirect semiconductor, silicon exhibits weak absorption for infrared photons and the efficient absorption of the full above bandgap solar spectrum requires careful photon management. This review paper provides an overview on the fundamental physics of light trapping and explains known theoretical limits.
The high occurrence of trapped unreactive charges due to chemical defects seriously affects the performance of g‐C3N4 in photocatalytic applications. This problem can be overcome by introducing ...ultrasmall red phosphorus (red P) crystals on g‐C3N4 sheets. The elemental red P atoms reduce the number of defects in the g‐C3N4 structure by forming new chemical bonds for much more effective charge separation. The product shows significantly enhanced photocatalytic activity toward hydrogen production. To the best of our knowledge, the hydrogen evolution rate obtained on this hybrid should be the highest among all P‐containing g‐C3N4 photocatalysts reported so far. The trapping and detrapping processes in this red P/g‐C3N4 system are thoroughly revealed by using time‐resolved transient absorption spectroscopy.
Chemical bonding of elemental red phosphorus (red P) remediates the chemical defects in g‐C3N4 structure. This would effectively suppress the charges trapping and prolong the lifetime of active charges in g‐C3N4 during the photocatalytic applications. This optimized red P/g‐C3N4 composite holds the highest record toward photocatalytic hydrogen production in the reported P‐containing g‐C3N4 systems to date.
•Behaviors of e− and h+ at TiO2 powder-defects were studied by laser spectroscopy.•e− trapping proceeds within a few ps at the defects on rutile and brookite TiO2.•Electron trapping elongate the ...lifetime of h+ to enhance the photocatalytic oxidation.•Moderate depth is important to obtain maximum activity under steady-state condition.•The depth of e− trap is shallower in the order of anatase < brookite < rutile.
Photocatalytic reactions are governed by photogenerated charge carriers upon band gap excitation. Therefore, for better understanding of the mechanism, the dynamics of photocarriers should be studied. One of the attractive materials is TiO2, which has been extensively investigated in the field of photocatalysis. This review article summarizes our recent works of time-resolved visible to mid-IR absorption measurements to elucidate the difference of anatase, rutile, and brookite TiO2 powders. The distinctive photocatalytic activities of these polymorphs are determined by the electron-trapping processes at the defects on powders. Powders are rich in defects and these defects capture photogenerated electrons. The depth of the trap is crystal phase dependent, and they are estimated to be < 0.1 eV, ∼0.4 eV and ∼0.9 eV for anatase, brookite, and rutile, respectively. Electron trapping reduces probability to meet with holes and then elongate the lifetime of holes. Therefore, it works negatively for the reaction of electrons but positively works for the reaction of holes. In the steady-state reactions, both electrons and holes should be consumed. Hence, the balance between the positive and negative effects of defects determines the distinctive photocatalytic activities of anatase, rutile, and brookite TiO2 powders.
The paramount parameters to determine the electrical output of triboelectric nanogenerator (TENG) are the surface triboelectric charges and the electrostatic induced transferred charges between ...triboelectric layer and electrode. However, diffusion of surface charge into the triboelectric layer reduces the surface charge density and thus weakens the electrostatic induction effect. In this work, we present a multifunctional layered TENG (ML-TENG) with an addition of reduced graphene oxide and Ag nanoparticles hybrid layer between a PVDF membrane triboelectric layer and bottom Al electrode to trap and block the interfacial charges. The output performance of ML-TENGs significantly yields 50 μC m−2 in charge density, which is improved by 500% compared with that of a traditional TENG. The surface potential of the PVDF membrane before triboelectrification drops with the insertion of the rGO-AgNPs hybrid layer, demonstrating the larger triboelectric potential difference and a better output performance. The trapping effect of rGO caused by sp2-hybrid structured carbon-atom coupled with the enhanced polarization effect by AgNPs to prevent interfacial charges from diffusing and drifting, providing efficient enhancements in TENG output. The output peak power from the TENG with a rGO-AgNPs hybrid layer reaches approximately 5.4 mW, which is 67.5 times that of a pristine TENG. Finally, the mechanism of the rGO-AgNPs layer working as the charge-trapping-blocking sites has been investigated and elaborated. It is anticipated to offer a new insight to the material science and device structure design for improving the performance of triboelectric devices.
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•A multifunctional-layered triboelectric nanogenerator (ML-TENG) based on the PVDF film and filtrated rGO-AgNPs layer for significant enhancement in surface charge density is proposed.•The trapping effect of rGO caused by sp2-hybrid structured carbon-atom coupled with the enhanced polarization effect by AgNPs to prevent interfacial charges from diffusing and drifting.•The mechanism of the rGO-AgNPs hybrid layer working as charge-trapping-blocking sites has been investigated.
Hydrogen embrittlement in metals (HE) is a serious challenge for the use of high strength materials in engineering practice and a major barrier to the use of hydrogen for global decarbonization. Here ...we describe the factors and variables that determine HE susceptibility and provide an overview of the latest understanding of HE mechanisms. We discuss hydrogen uptake and how it can be managed. We summarize hydrogen trapping and the techniques used for its characterization. We also review literature that argues that hydrogen trapping can be used to decrease HE susceptibility. We discuss the future research that is required to advance the understanding of HE and hydrogen trapping and to develop HE-resistant alloys.
•This review provides a summary of basic theories on hydrogen embrittlement and recent advancements in related research.•The review addresses common misconceptions about hydrogen embrittlement problems and provides clarification.•The paper discusses a multiscale perspective on the challenge and explores the proposed solution to hydrogen trapping.
When CO2 is injected into sedimentary basins, the fate of the buoyant CO2 will be determined by how it interacts with the underlying geologic heterogeneities. Here we geologically print a ...cross‐bedded pattern using two different bead sizes, and then conduct flow experiments to observe buoyant flow pathways, migration speed, and immobilized volumes. The amount of buoyant phase trapped under the heterogeneities is observed to vary by two orders of magnitude, with the controlling parameter being the size contrast between the coarse and fine grains that make up the structure. The results allow an estimate of heterogeneity trapping, and show how CO2 trapping in aquifers can be experimentally evaluated before injection.
Plain Language Summary
Geologic CO2 storage is expected to play a significant role in our efforts to rapidly reduce greenhouse gas emissions. When the captured CO2 is injected deep into the subsurface, its subsequent movement is affected by the underlying rock formations. In particular small variations in rock properties can cause large changes in CO2 migration. In this study, we print geologic replicas in a thin 2D glass tank and flow CO2 mimicking fluid through the replicas. The movement of the fluid is visualized in real time and we quantify the amount of fluid trapped using advanced image analysis. We show that subtle changes in rock properties, especially the grain size contrast, can slow down migration speeds and increase trapped volumes by 10–100 times. Our results also show that heterogeneities can contribute up to 80% of the total storage capacity. These observations underscore the importance of accounting for small scale heterogeneities in future CO2 storage studies.
Key Points
We conduct unique intermediate‐scale, two phase flow experiments in cross‐bedded heterogeneous bead packs to study CO2 migration and trapping
Using real time visualization, we illuminate dynamic flow processes at the meter scale
Changes in grain size contrast of crossbeds drastically affect migration times and trapped volumes of CO2
Optical tweezers and associated manipulation tools in the far field have had a major impact on scientific and engineering research by offering precise manipulation of small objects. More recently, ...the possibility of performing manipulation with surface plasmons has opened opportunities not feasible with conventional far-field optical methods. The use of surface plasmon techniques enables excitation of hotspots much smaller than the free-space wavelength; with this confinement, the plasmonic field facilitates trapping of various nanostructures and materials with higher precision. The successful manipulation of small particles has fostered numerous and expanding applications. In this paper, we review the principles of and developments in plasmonic tweezers techniques, including both nanostructure-assisted platforms and structureless systems. Construction methods and evaluation criteria of the techniques are presented, aiming to provide a guide for the design and optimization of the systems. The most common novel applications of plasmonic tweezers, namely, sorting and transport, sensing and imaging, and especially those in a biological context, are critically discussed. Finally, we consider the future of the development and new potential applications of this technique and discuss prospects for its impact on science.
Quantum processing architectures that include multiple qubit modalities offer compelling strategies for high-fidelity operations and readout, quantum error correction, and a path for scaling to large ...system sizes. Such hybrid architectures have been realized for leading platforms, including superconducting circuits and trapped ions. Recently, a new approach for constructing large, coherent quantum processors has emerged based on arrays of individually trapped neutral atoms. However, these demonstrations have been limited to arrays of a single atomic element where the identical nature of the atoms makes crosstalk-free control and nondemolition readout of a large number of atomic qubits challenging. Here we introduce a dual-element atom array with individual control of single rubidium and cesium atoms. We demonstrate their independent placement in arrays with up to 512 trapping sites and observe negligible crosstalk between the two elements. Furthermore, by continuously reloading one atomic element while maintaining an array of the other, we demonstrate a new continuous operation mode for atom arrays without any off-time. Our results enable avenues for auxiliary-qubit-assisted quantum protocols such as quantum nondemolition measurements and quantum error correction, as well as continuously operating quantum processors and sensors.
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