Byron Cocilovo

Temporal, spectral, and spatial study of the automated vicarious calibration test site at Railroad Valley, Nevada

The Remote Sensing Group at the University of Arizona has developed an automated methodology and instrument suite to measure the surface reflectance of the vicarious calibration test site at Railroad Valley, Nevada. Surface reflectance is a critical variable used as one of the inputs into a radiative transfer code to predict the top-of-atmosphere radiance, and inexpensive and robust ground-viewing radiometers have been present at the site since 2004. The goal of the automated approach is to retain RSGs current 2-3% level of uncertainty while increasing the number of data sets collected throughout the year without the need for on-site personnel. A previous study was completed to determine if the number and positions of the four radiometers were adequate to spatially sample the 1-km2 large-footprint site at Railroad Valley. The preliminary study utilized one set of panchromatic data from Digital Globes QuickBird satellite. Results from this one day showed that the positions of the four ground-viewing radiometers adequately sample the site. The work presented here expands in a spectral and temporal sense by using high-spatial-resolution data from Ikonos, QuickBird, and Landsat-7 ETM+ to determine if the locations of the ground-viewing radiometers correctly sample the site. The multispectral capability of these sensors is used to establish if there are any spectral effects, which will also help RSG to determine what spectral bands should be chosen for the new ground-viewing radiometers that are currently in development for the automated test site at Railroad Valley.

Effect of modular diffraction gratings on absorption in P3HT:PCBM layers

Various gratings with 700 nm feature spacings are patterned on the reverse side of organic solar cell active layers to increase the path length and constrain light to the cell through total internal reflection. The absorption enhancement is studied for 15, 40, and 120 nm active layers. We were able to confine 9% of the incident light over the wavelength range of 400-650 nm, with thinner gratings having a greater enhancement potential. The measurement setup utilizing an integrating sphere to fully characterize scattered or diffracted light is also fully described.

Designing spectrum-splitting dichroic filters to optimize current-matched photovoltaics

We have developed an approach for designing a dichroic coating to optimize performance of current-matched multijunction photovoltaic cells while diverting unused light. By matching the spectral responses of the photovoltaic cells and current matching them, substantial improvement to system efficiencies is shown to be possible. A design for use in a concentrating hybrid solar collector was produced by this approach, and is presented. Materials selection, design methodology, and tilt behavior on a curved substrate are discussed.

Light harvesting in organic solar cells using a nanostructured ITO grating

Nanostructured ITO gratings have been used in organic solar cells to enhance light absorption in a thin active layer of PCBM:P3HT via light harvesting. An additional peak at 680-700 nm in the absorption spectrum of the active layer appears, resulting in enhanced broadband absorption compared to the planar counterpart. FDTD simulation of the cell supports the experimental results and shows the grating effectively increases the electric field in the active layer.

Tolerance Analysis and Characterization of Hybrid Thermal-PV Solar Trough Prototype

Hybrid thermal-PV solar trough collectors combine concentrated photovoltaics and concentrated solar power technology. In this work, we analyze the optical and mechanical tolerances that affect the solar energy collection using non-sequential ray tracing techniques. The study is complemented with a half scale prototype characterization. We aim to establish a basis for tolerances required for fabrication and manufacturing of such systems.

Surface-Enhanced Two-Photon Excitation Fluorescence of Various Fluorophores Evaluated Using a Multiphoton Microscope

We present a rapid, low-power testbed for the detection and imaging of fluorescent probes utilizing two-photon excitation fluorescence (2PEF). The 2PEF signal from fluorophores commonly used in biological imaging have been enhanced using plasmonic substrates that have been designed to have a high plasmonic resonance over a narrow band that matches the source. The samples were illuminated and imaged using a low-power, in-house multiphoton microscope. A green fluorescent protein (bfloGFPa1), chlorophyll, or rhodamine 6G were deposited onto the plasmonic substrates and their 2PEF signals were measured relative to planar samples. The fluorescence intensities from the green fluorescent protein, chlorophyll, and rhodamine were enhanced by factors of 50, 8, and 4, respectively, with the structured substrates (relative to the planar substrates).

Multiphoton Microscopy Characterization of Plasmonic Enhanced Nanodevices

We apply our custom-designed multiphoton-microscope to investigate the plasmonic E-field-enhancement of planar and textured gold and silver layers on detected signals. Compact laser sources at 1560nm and 1040nm are used to perform the microscopy.

The Effect of Diffraction Gratings on Absorption in P3HT:PCBM Layers

An integrating sphere is used to measure the absorptance of P3HT:PCBM layers with 700 nm period gratings on the reverse side of the substrate. Gratings that do not exploit TIR adversely affect the absorptance.