90 research outputs found
Calculating Lost Profit Damages: The Missouri Supreme Court Semi-Fixed the Variable Appellate Caselaw
Prior to Ameristar Jet Charter, Inc. v. Dodson International Parts, Inc., a split of authority existed among appellate cases in Missouri as to how to calculate lost profit damages. One line of cases stood for the proposition that all overhead expenses, including fixed expenses, should be deducted from estimated lost revenues to determine lost profit damages. Another set of cases explicitly refused to deduct all overhead; those courts only deducted variable expenses from estimated lost revenue to determine lost profit damages. The Missouri Supreme Court resolved this conflict in a unanimous decision in Ameristar. The court held that fixed expenses should not be deducted from the estimation of lost revenues in the calculation of lost profit damages. This decision achieves the theory behind damage awards; it puts the plaintiff in as good a position as he would have been had the tort not been committed. The holding presents a problem, not in its reasoning, but in the rigidity of its terminology. A plaintiff will not be put in as good a position as he was before by the deduction of only variable expenses from estimated lost revenues in many cases. Some cases, like Ameristar, may involve a third type of cost, termed by cost accountants as step function or semi fixed costs. Furthermore, in other cases the deduction of fixed expenses may be appropriate. The calculation of lost profit damages should focus on deducting the costs actually saved by the defendant, rather than on the classification of the different expenses as fixed or variable. An additional problem presented by the decision is the court\u27s ambiguity as to whether the classification of expenses as fixed or variable is a question of law or fact
Scalable Nanophotonic Light Management Design for Solar Cells
The current trend in wide adoption of solar energy is encouraging in the context of current projections of increasing energy consumption and the dire need to decrease carbon emissions. The solar industry has expanded due to scientific advances in the power conversion efficiency of solar modules. In order maintain a rapid pace of adoption and further decrease electricity costs, converting each photon becomes increasingly important. This work focuses on nanophotonic approaches to increasing the power conversion efficiency of different solar photovoltaic designs. The projects voluntarily impose certain design constraints in order to be compatible with the large scale manufacturing needed by the solar industry. A focus was given to designs that can leverage the promising technology of nanoimprint lithography. Amorphous silicon tandem cells with embedded nanophotonic patterning attempted to increase absorption while minimizing materials and time costs. Simulated designs of Copper Indium Gallium Diselenide absorbers showed that the management of excited carriers is equally as important as light management in decreasingly thin absorber layers. Near perfect anti-reflection structures were given a detailed physical analysis to better describe the fundamental physics of near zero reflection due to nanocones printed on solar cell encapsulation glass. Experimental results agreed with the theoretical analysis, and showed that these nanostructures further increased absorbed photocurrent by trapping light in the encapsulation glass. Finally, a unique device in the form of a tandem luminescent solar concentrator/silicon solar module was proposed and analyzed as a low cost and adaptable technology for increased solar power conversion efficiency. Key to this design was discovery of new, near-perfect components for light management. Exciting and innovative designs are proposed to control the light-matter interaction within these devices. Study of a photonic luminescent solar concentrator predicted that luminescence can be trapped in photonic crystal slab waveguides with near zero loss. Rigorous experimental efforts to characterize a multitude of near-perfect samples help guide these designs toward their final goals
Three-dimensional nanoimprint lithography using two-photon lithography master samples
We demonstrate three-dimensional (3-D) nanoimprint lithography using master samples initially structured by two-photon lithography. Complex geometries like micro prisms, micro parabolic concentrators, micro lenses and other micrometer sized objects with nanoscale features are three-dimensionally fabricated using two-photon lithography. Stamps made out of polydimethylsiloxane are then cast using the two-photon lithographically structured samples as master samples. Hereby, expensive serial nano 3-D printing is transformed into scalable parallel 3-D nanoimprint lithography. Furthermore, the transition from two-photon lithography to imprint lithography increases the freedom in substrate and ink choice significantly. We demonstrate printing on textured surfaces as well as residue-free printing with silver ink using capillary action
Near-Unity Unselective Absorption in Sparse InP Nanowire Arrays
We experimentally demonstrate near-unity, unselective absorption, broadband, angle-insensitive, and polarization-independent absorption, in sparse InP nanowire arrays, embedded in flexible polymer sheets via geometric control of waveguide modes in two wire motifs: (i) arrays of tapered wires and (ii) arrays of nanowires with varying radii. Sparse arrays of these structures exhibit enhanced absorption due to strong coupling into the first order azimuthal waveguide modes of individual nanowires; wire radius thus controls the spectral region of the absorption enhancement. Whereas arrays of cylindrical wires with uniform radius exhibit narrowband absorption, arrays of tapered wires and arrays with multiple wire radii expand this spectral region and achieve broadband absorption enhancement. Herein, we present an economic, top-down lithographic/etch fabrication method that enables fabrication of multiple InP nanowire arrays from a single InP wafer with deliberate control of nanowire radius and taper. Using this method, we create sparse tapered and multiradii InP nanowire arrays and demonstrate optical absorption that is broadband (450–900 nm), angle-insensitive, and near-unity (>90%) in roughly 100 nm planar equivalence of InP. These highly absorbing sparse nanowire arrays represent a promising approach to flexible, high efficiency optoelectronic devices, such as photodetectors, solar cells, and photoelectrochemical devices
Spectrally Matched Quantum Dot Photoluminescence in GaAs-Si Tandem Luminescent Solar Concentrators
Luminescent solar concentrators (LSCs) can capture both direct and diffuse irradiance via isotropic absorption of waveguide-embedded luminophores. Additionally, LSCs have the potential to reduce the overall cost of a photovoltaic (PV) module by concentrating incident irradiance onto an array of smaller cells. Historically, LSC efficiencies have suffered in part from incomplete light absorption and non-unity quantum yield (QY) of the luminophores. Inorganic quantum dot (QD) luminophores allow the spectral tuning of the absorption and photoluminescence bands, and have near-unity QYs. In a four-terminal tandem LSC module scheme, visible light is trapped within the LSC waveguide and is converted by GaAs cells, and near infrared light is optically coupled to a Si subcell. Here, we investigate the efficiency of a GaAs/Si tandem LSC as a function of luminophore absorption edge and emission wavelength for QD luminophores dispersed in an LSC waveguide with embedded, coplanar GaAs cells. We find that positioning the luminophore absorption edge at 660 nm yields a maximum module power efficiency of approximately 26%, compared with 21% for the non-optimized luminophore and 19% for the bare Si cases
Micro-optical Tandem Luminescent Solar Concentrators
Traditional concentrating photovoltaic (CPV) systems utilize multijunction
cells to minimize thermalization losses, but cannot efficiently capture diffuse
sunlight, which contributes to a high levelized cost of energy (LCOE) and
limits their use to geographical regions with high direct sunlight insolation.
Luminescent solar concentrators (LSCs) harness light generated by luminophores
embedded in a light-trapping waveguide to concentrate light onto smaller cells.
LSCs can absorb both direct and diffuse sunlight, and thus can operate as flat
plate receivers at a fixed tilt and with a conventional module form factor.
However, current LSCs experience significant power loss through parasitic
luminophore absorption and incomplete light trapping by the optical waveguide.
Here we introduce a tandem LSC device architecture that overcomes both of these
limitations, consisting of a PLMA polymer layer with embedded CdSe/CdS quantum
dot (QD) luminophores and InGaP micro-cells, which serve as a high bandgap
absorber on top of a conventional Si photovoltaic. We experimentally synthesize
CdSe/CdS QDs with exceptionally high quantum-yield (99%) and ultra-narrowband
emission optimally matched to fabricated III-V InGaP micro-cells. Using a Monte
Carlo ray-tracing model, we show the radiative limit power conversion
efficiency for a module with these components to be 30.8% diffuse sunlight
conditions. These results indicate that a tandem LSC-on-Si architecture could
significantly improve upon the efficiency of a conventional Si photovoltaic
module with simple and straightforward alterations of the module lamination
steps of a Si photovoltaic manufacturing process, with promise for widespread
module deployment across diverse geographical regions and energy markets
High Spectral Resolution Plasmonic Color Filters with Subwavelength Dimensions
Rapid advances in image sensor technology have generated a mismatch between the small size of image sensor pixels and the achievable filter spectral resolution. This mismatch has prevented the realization of chip-based image sensors with simultaneously high spatial and spectral resolution. We report here a concept that overcomes this trade-off, enabling high spectral resolution (transmission FWHM <31 nm) filters with subwavelength dimensions operating at optical and near-infrared wavelengths. An inverse design methodology was used to realize a new type of plasmonic cavity that efficiently couples an in-plane Fabry–Perot resonator to a single plasmonic slit that supports surface plasmon polaritons. This design principle, combined with a new metal imprinting method that yields metallic nanostructures with both top and bottom surfaces that are extremely smooth, enabled demonstration of high spectral resolution transmission filters with smaller area than any previously reported
Effectively Transparent Front Contacts for Optoelectronic Devices
Effectively transparent front contacts for optoelectronic devices achieve a measured transparency of up to 99.9% and a measured sheet resistance of 4.8 Ω sq^(−1). The 3D microscale triangular cross-section grid fingers redirect incoming photons efficiently to the active semiconductor area and can replace standard grid fingers as well as transparent conductive oxide layers in optoelectronic devices
Photonic Crystal Waveguides for >90% Light Trapping Efficiency in Luminescent Solar Concentrators
Luminescent solar concentrators are currently limited in their potential concentration factor and solar conversion efficiency by the inherent escape cone losses present in conventional planar dielectric waveguides. We demonstrate that photonic crystal slab waveguides tailored for luminescent solar concentrator applications can exhibit >90% light trapping efficiency. This is achieved by use of quantum dot luminophores embedded within the waveguide that absorb light at photon energies corresponding to photonic crystal leaky modes that couple to incoming sunlight. The luminophores then emit at lower photon energies into photonic crystal bound modes that enable highly efficient light trapping in slab waveguides of wavelength-scale thickness. Photonic crystal waveguides thus nearly eliminate escape cone losses, and overcome the performance limitations of previously proposed wavelength-selective dielectric multilayer filters. We describe designs for hole-array and rod-array photonic crystals comprised of hydrogenated amorphous silicon carbide using CdSe/CdS quantum dots. Our analysis suggests that photonic crystal waveguide luminescent solar concentrators using these materials these can achieve light trapping efficiency above 92% and a concentration factor as high as 100
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