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Abstract One hypothesized mechanism that triggers deep‐focus earthquakes in oceanic subducting slabs below ∼300 km depth is transformational faulting due to the olivine‐to‐spinel phase transition. This study uses finite element modeling to investigate phase transformation‐induced stress redistribution and material weakening in olivine. A thermodynamically consistent constitutive model is developed to capture the evolution of phase transformation in olivine under different pressure and temperature conditions. The overall numerical model enables considering multiscale material features, including the polycrystalline structure, mesoscale heterogeneity, and various phases or variants of phases at the microscopic level, and accounts for viscoplastic behaviors with thermo‐mechanical coupling effects. The model is validated with several benchmarks, including a phase diagram of phase transformation from olivine to spinel. The validated model is used to study the interactive behaviors between defects (heterogeneity) and phase transformation. The simulation results reveal that spinel formation under pressure initiates near inclusions and along the grain boundaries, consistent with experimental observations. At lower temperatures, the transformation leads to the formation of thin conjugate bands of spinel diagonal to the compression loading direction. Local stress analysis along these bands also suggests the initiation of faulting. In contrast, the numerical results at higher transformation rates show that significant spinel formation occurs over a larger area at elevated temperatures, leading to ductile behavior, which agrees with experimental findings. Numerical simulation of multiple inclusions under confined pressure also shows the formation of a network of spinel bands resembling phase‐transformation patterns observed in the laboratory experiments. Additionally, stress softening patterns due to phase transformation are similar to experimental observations. 

Herein, we focus on the design, synthesis, and characterization of thienothiadiazole (TTD)-based near-infrared II (NIR-II) theranostic fluorophores and their nanoparticles. 

Abstract Spatially resolved vibrational mapping of nanostructures is indispensable to the development and understanding of thermal nanodevices 1 , modulation of thermal transport 2 and novel nanostructured thermoelectric materials 3–5 . Through the engineering of complex structures, such as alloys, nanostructures and superlattice interfaces, one can significantly alter the propagation of phonons and suppress material thermal conductivity while maintaining electrical conductivity 2 . There have been no correlative experiments that spatially track the modulation of phonon properties in and around nanostructures due to spatial resolution limitations of conventional optical phonon detection techniques. Here we demonstrate two-dimensional spatial mapping of phonons in a single silicon–germanium (SiGe) quantum dot (QD) using monochromated electron energy loss spectroscopy in the transmission electron microscope. Tracking the variation of the Si optical mode in and around the QD, we observe the nanoscale modification of the composition-induced red shift. We observe non-equilibrium phonons that only exist near the interface and, furthermore, develop a novel technique to differentially map phonon momenta, providing direct evidence that the interplay between diffuse and specular reflection largely depends on the detailed atomistic structure: a major advancement in the field. Our work unveils the non-equilibrium phonon dynamics at nanoscale interfaces and can be used to study actual nanodevices and aid in the understanding of heat dissipation near nanoscale hotspots, which is crucial for future high-performance nanoelectronics. 

Abstract Visibly transparent luminescent solar concentrators (TLSC) have the potential to turn existing infrastructures into net-zero-energy buildings. However, the reabsorption loss currently limits the device performance and scalability. This loss is typically defined by the Stokes shift between the absorption and emission spectra of luminophores. In this work, the Stokes shifts (SS) of near-infrared selective-harvesting cyanines are altered by substitution of the central methine carbon with dialkylamines. We demonstrate varyingSSwith values over 80 nm and ideal infrared-visible absorption cutoffs. The corresponding TLSC with such modification shows a power conversion efficiency (PCE) of 0.4% for a >25 cm²device area with excellent visible transparency >80% and up to 0.6% PCE over smaller areas. However, experiments and simulations show that it is not the Stokes shift that is critical, but the total degree of overlap that depends on the shape of the absorption tails. We show with a series ofSS-modulated cyanine dyes that theSSis not necessarily correlated to improvements in performance or scalability. Accordingly, we define a new parameter, the overlap integral, to sensitively correlate reabsorption losses in any LSC. In deriving this parameter, new approaches to improve the scalability and performance are discussed to fully optimize TLSC designs to enhance commercialization efforts. 

Abstract Visibly transparent luminescent solar concentrators (TLSC) can optimize both power production and visible transparency by selectively harvesting the invisible portion of the solar spectrum. Since the primary applications of TLSCs include building envelopes, greenhouses, automobiles, signage, and mobile electronics, maintaining aesthetics and functionalities is as important as achieving high power conversion efficiencies (PCEs) in practical deployment. In this work, massive‐downshifting phosphorescent nanoclusters and fluorescent organic molecules are combined into a TLSC system as ultraviolet (UV) and near‐infrared (NIR) selective‐harvesting luminophores, respectively, demonstrating UV and NIR dual‐band selective‐harvesting TLSCs with PCE over 3%, average visible transmittance (AVT) exceeding 75% and color metrics suitable for the window industry. With distinct wavelength‐selectivity and effective utilization of the invisible portion of the solar spectrum, this work reports the highest light utilization efficiency (PCE × AVT) of 2.6 for a TLSC system, the highest PCE of any transparent photovoltaic (TPV) devices with AVT greater than 70%, and outperforms the practical limit for non‐wavelength‐selective TPV. 

Abstract Transparent luminescent solar concentrators (TLSCs) selectively harvest ultraviolet and near‐infrared photons. Due to the absence of electrodes, busbars, and collection grids over the solar harvesting area, the device structure enables these devices to achieve the highest levels of transparency and aesthetics. Recently, CO_i8DFIC has been developed as a nonfullerene acceptor in organic photovoltaics with unprecedented performance. In this work, nonfullerene acceptors are introduced into TLSCs as the luminophores. The impact of CO_i8DFIC concentration on power conversion efficiency (PCE), aesthetic quality, and scalability is systematically studied. After device optimization, the CO_i8DFIC TLSCs are shown to achieve a PCE over 1.2% while the average visible transmittance exceeds 74% and color rendering index exceeds 80. This work reports the highest TLSC device efficiency at the highest visibly transparency and highlights that the photoluminescent properties of these emerging low bandgap organic molecules providing an encouraging path to higher TLSC performance.