The Use of Nanostructured Calcium Silicate in Solar Cells

<p>Nanostructured calcium silicate (NCaSil) had previously been found to be photoactive and mildly semiconducting. Its use in solar cells was investigated in this project. Many different types of solar cells exist. Most common on the market are silicon-based cells, which generate charge separation through electric fields at p/n junctions. Over the last decade, dye-sensitised solar cells (DSSCs) have been heavily researched. DSSCs depend on effective electron/hole separation at the dye and efficient transfer to the electron- and hole-conducting materials. An older and little-researched form of cells is the photogalvanic cell, of which there are two forms. One contains a semiconducting material, whereas the other comprises of either one or two redox couples, in which at least one species is photoactive. An example of the latter form of cell is the odide/triiodide redox couple, which is commonly the electrolyte of choice in DSSCs and semiconductor-containing photogalvanic cells. This project predominantly investigated the use of NCaSil in conjunction with the iodide/triiodide redox couple and its use in solar cells. The project ascertained that, when used with the iodide/triiodide, the NCaSil did not act as a semiconducting material (either as in a DSSC or semiconductor photogalvanic cell). Rather iodide/triiodide's photogalvanic process dominated the cell, despite the presence of NCaSil. Furthermore, the addition of the stable NCaSils to the iodide/triiodide (with 5 wt% CaCl2) created "soggy sand electrolytes". These electrolytes showed increased conductivities, despite their higher viscosities, due to a synergistic effect. Soggy sand electrolytes show great promise in the development of more solid-like DSSCs. Furthermore, the project observed that the performance of NCaSil cells was maximized with a 70 wt% ethanol (30 wt% water) solvated electrolyte, with 1.5 wt% CaCl2 added to this electrolyte (or 5 wt % CaCl2 in the water content). When used long-term in conjunction with Reinforced NCaSil, a gel was formed, which showed promising activity. This activity was attributed to the interaction of surface-bound Ca2+ to iodine. Similar gels formed from vanadium- and cerium-treated NCaSil also showed great cell performance. Cell performance was further enhanced by backing the cell with a reflective or light scattering material, such as Teflon tape.</p>

The Use of Nanostructured Calcium Silicate in Solar Cells

<p>Nanostructured calcium silicate (NCaSil) had previously been found to be photoactive and mildly semiconducting. Its use in solar cells was investigated in this project. Many different types of solar cells exist. Most common on the market are silicon-based cells, which generate charge separation through electric fields at p/n junctions. Over the last decade, dye-sensitised solar cells (DSSCs) have been heavily researched. DSSCs depend on effective electron/hole separation at the dye and efficient transfer to the electron- and hole-conducting materials. An older and little-researched form of cells is the photogalvanic cell, of which there are two forms. One contains a semiconducting material, whereas the other comprises of either one or two redox couples, in which at least one species is photoactive. An example of the latter form of cell is the odide/triiodide redox couple, which is commonly the electrolyte of choice in DSSCs and semiconductor-containing photogalvanic cells. This project predominantly investigated the use of NCaSil in conjunction with the iodide/triiodide redox couple and its use in solar cells. The project ascertained that, when used with the iodide/triiodide, the NCaSil did not act as a semiconducting material (either as in a DSSC or semiconductor photogalvanic cell). Rather iodide/triiodide's photogalvanic process dominated the cell, despite the presence of NCaSil. Furthermore, the addition of the stable NCaSils to the iodide/triiodide (with 5 wt% CaCl2) created "soggy sand electrolytes". These electrolytes showed increased conductivities, despite their higher viscosities, due to a synergistic effect. Soggy sand electrolytes show great promise in the development of more solid-like DSSCs. Furthermore, the project observed that the performance of NCaSil cells was maximized with a 70 wt% ethanol (30 wt% water) solvated electrolyte, with 1.5 wt% CaCl2 added to this electrolyte (or 5 wt % CaCl2 in the water content). When used long-term in conjunction with Reinforced NCaSil, a gel was formed, which showed promising activity. This activity was attributed to the interaction of surface-bound Ca2+ to iodine. Similar gels formed from vanadium- and cerium-treated NCaSil also showed great cell performance. Cell performance was further enhanced by backing the cell with a reflective or light scattering material, such as Teflon tape.</p>

Modeling with Multiple Correlated Spectral Data Based on Approximating the Nonlinear Spectrum Induced by Scattering

In the spectral quantitative analysis of scattering solution, the improvement of accuracy is seriously restricted by the nonlinearity caused by scattering, and even the measurement will fail due to the influence of scattering. The important reasons are that the modeling variables are greatly affected by nonlinearity, and the information contained in the modeling data cannot represent the scattering characteristics. In this paper, a method is proposed, in which the spectral data of several optical pathlengths with equal space are combined as the modeling data set of a sample. These highly correlated spectral data contain relatively nonlinear information. The addition of the spectral data provides more options for the selection of principal components in modeling with PLS method. By giving lower weight to the corresponding wavelength which is greatly affected by scattering, the model is insensitive to scattering and the prediction accuracy is improved. Through the spectral quantitative analysis experiment on strong scattering material, the prediction accuracy of the model was 61.7% higher than that of the traditional method and was 58.5% higher than that of the variable sorting for normalization method. The feasibility of the method is verified.

Optical computation of a spin glass dynamics with tunable complexity

Spin glasses (SGs) are paradigmatic models for physical, computer science, biological, and social systems. The problem of studying the dynamics for SG models is nondetermistic polynomial-time (NP) hard; that is, no algorithm solves it in polynomial time. Here we implement the optical simulation of an SG, exploiting the N segments of a wavefront-shaping device to play the role of the spin variables, combining the interference downstream of a scattering material to implement the random couplings between the spins (the Jij matrix) and measuring the light intensity on a number P of targets to retrieve the energy of the system. By implementing a plain Metropolis algorithm, we are able to simulate the spin model dynamics, while the degree of complexity of the potential energy landscape and the region of phase diagram explored are user defined, acting on the ratio P/N=α. We study experimentally, numerically, and analytically this Hopfield-like system displaying a paramagnetic, ferromagnetic, and SG phase, and we demonstrate that the transition temperature Tg to the glassy phase from the paramagnetic phase grows with α. We demonstrate the computational advantage of the optical SG where interaction terms are realized simultaneously when the independent light rays interfere on the detector’s surface. This inherently parallel measurement of the energy provides a speedup with respect to purely in silico simulations scaling with N.

Observations on aerosol optical properties and scavenging during cloud events

Long-term statistics of atmospheric aerosol and especially cloud scavenging were studied at the Puijo measurement station in Kuopio, Finland, during October 2010–November 2014. Aerosol size distributions, scattering coefficients at three different wavelengths (450, 550, and 700 nm), and absorption coefficient at wavelength 637 nm were measured with a special inlet system to sample interstitial and total aerosol in clouds. On average, accumulation mode particle concentration was found to be correlated with temperature with the lowest average concentrations of 200 cm−3 around 0 ∘C increasing to 800 cm−3 at 20 ∘C. The scavenging efficiencies of both scattering and absorbing material were observed to have a slightly positive temperature correlation in in-cloud measurements. At 0 ∘C, the scavenging efficiencies of scattering and absorbing material were 0.85 and 0.55 with slopes of 0.005 and 0.003 ∘C−1, respectively. Scavenging efficiencies were also studied as a function of the diameter at which half of the particles are activated into cloud droplets. This analysis indicated that there is a higher fraction of absorbing material, typically black carbon, in smaller sizes so that at least 20 %–30 % of interstitial particles within clouds consist of absorbing material. In addition, the PM1 inlet revealed that approximately 20 % of absorbing material was observed to reside in particles with ambient diameter larger than ∼ 1 µm at relative humidity below 90 %. Similarly, 40 % of scattering material was seen to be in particles larger than 1 µm. Altogether, this dataset provides information on the size-dependent aerosol composition and in-cloud scavenging of different types of aerosol. The dataset can be useful in evaluating how well the size-dependent aerosol composition is simulated in global aerosol models and how well these models capture the in-cloud scavenging of different types of aerosol in stratus clouds.

CODE VERIFICATION OF MPACT USING GANAPOL CRITICAL ROD BENCHMARK

This work is dedicated to the code verification of MPACT, which is developed under the Consortium for Advanced Simulation of Light Water Reactors by the University of Michigan and Oak Ridge National Laboratory, where the numerical solution is compared to the reference solution of a benchmark problem with a known analytical solution. In this work, Benchmark Problem 3.4 in Barry Ganapol’s benchmark book was chosen as an MOC code verification test problem. Problem 3.4 is a bare cylinder of infinite height, which is an excellent benchmark problem for 2D MOC. To ensure that this benchmark problem exercised the same code as typically used by MPACT, the bare rod configuration was surrounded by a bounding box filled with a non-scattering material. To avoid implementing a critical rod search in the MPACT code, the MPACT analysis was performed using cross sections that yielded the given c, the average number of secondary neutrons per collision, and a rod radius that was the corresponding critical rod radius. MPACT agreed with all cases to within a few pcm. The convergence behavior was studied. The results show a 2nd order radial convergence, consistent with flat-source approximation. The convergence curves with respect to ray spacing and polar angle quadrature set order were also obtained. The other quantity of interest tabulated for Problem 3.4 was the radial distribution of the scalar flux. Two configurations were analyzed, and the resultant radial flux profiles agreed very well with the tabulated results. The verification of the production neutronics code MPACT has been augmented by the addition of the analytical solutions for an infinite cylinder from the Ganapol benchmark book. These test cases can be included in the regression suite for MPACT.

Measuring interstellar delays of PSR J0613−0200 over 7 yr, using the Large European Array for Pulsars

ABSTRACT Using data from the Large European Array for Pulsars, and the Effelsberg telescope, we study the scintillation parameters of the millisecond pulsar PSR J0613−0200 over a 7 yr timespan. The ‘secondary spectrum’ – the 2D power spectrum of scintillation – presents the scattered power as a function of time delay, and contains the relative velocities of the pulsar, observer, and scattering material. We detect a persistent parabolic scintillation arc, suggesting scattering is dominated by a thin, anisotropic region. The scattering is poorly described by a simple exponential tail, with excess power at high delays; we measure significant, detectable scattered power at times out to ${\sim}5 \, \mu {\rm s}$, and measure the bulk scattering delay to be between 50 to 200 ns with particularly strong scattering throughout 2013. These delays are too small to detect a change of the pulse profile shape, yet they would change the times of arrival as measured through pulsar timing. The arc curvature varies annually, and is well fitted by a one-dimensional scattering screen ${\sim}40{{\ \rm per\ cent}}$ of the way towards the pulsar, with a changing orientation during the increased scattering in 2013. Effects of uncorrected scattering will introduce time delays correlated over time in individual pulsars, and may need to be considered in gravitational wave analyses. Pulsar timing programmes would benefit from simultaneously recording in a way that scintillation can be resolved, in order to monitor the variable time delays caused by multipath propagation.

Observations on aerosol optical properties and scavenging during cloud events

Long term statistics of atmospheric aerosol and especially cloud scavenging were studied at the Puijo measurement station in Kuopio, Finland, during October 2010–November 2014. Aerosol size distributions, scattering coefficients at three different wavelengths (450 nm, 550 nm, and 700 nm), and absorption coefficient at wavelength 637 nm were measured with a special inlet system to sample interstitial and total aerosol in clouds. On average, accumulation mode particle concentration was found to be temperature dependent with lowest average concentrations of 200 cm−3 around 0 °C increasing to more than 800 cm−3 for temperatures higher than 20 °C. From the in-cloud measurements, both scattering and absorbing material scavenging efficiencies were observed to have slightly increasing temperature dependence. At 0 °C the efficiencies of scattering and absorbing matter were 0.85 and 0.55 with slopes of 0.005 °C−1 and 0.003 °C−1, respectively. Additionally, scavenging efficiencies were studied as a function of the diameter at which half of the particles are activated into cloud droplets. This analysis indicated that the is a higher fraction of absorbing material, typically black carbon, in smaller sizes so that at least 20–30 % of interstitial particles within clouds consist of absorbing material. In addition, the PM1-inlet revealed that approximately 20 % of absorbing material was observed to reside in particles with ambient diameter larger than ~ 1 µm at relative humidity below 90 %. Similarly, 40 % of scattering material was seen to be in particles larger than 1 µm. Altogether, this dataset provides information on size dependent aerosol composition that can be applied in evaluating how well large-scale aerosol models reproduce aerosol composition, especially with respect to scavenging in stratus clouds.

White Painting Pigment as a Low-Cost Light Scattering Material for Bilayer Photoelectrodes of Dye-Sensitized Solar Cells

White pigment (DuPont R902+) has been used as a light scattering material in the preparation of bilayerphotoelectrodes of dye-sensitized solar cells (DSCs). The X-ray diffraction (XRD) pattern of the white pigment revealed that the material consists of rutile phase of titanium dioxide. The light scattering layer prepared from the white pigment was coated onto the main-layer of the photo electrodes of DSCs. The solar cells with and without light scattering layer were tested in the simulated light of 100 mW/cm2. The DSCs with the light scattering layer generated more current density than the DSCs without scattering layer and the overall light to electric power conversion efficiency of DSCs with the light scattering layer was ~4.00 % compared with 3.25 % efficiency of the DSCs without the scattering layer.