Solar Concentrator Applications Research Articles

Characterization of cadmium sulfide light dependent resistors sensors for optical solar trackers

<span lang="EN-US">The aim of this paper is to study the effect of dissimilarity of the intrinsic characteristics of the light dependent resistor (LDRs) on optical sun tracking systems, designed for solar power concentration applications such as parabolic trough collectors, Fresnel mirrors concentrators, and concentrated photovoltaic, a comparative study was done between a sun tracker based on LDRs chosen randomly with and without an initial calibration of the offsets, and a sun tracker based on LDRs selected meticulously thanks to a black box test bench, developed especially for this purpose. By choosing two light dependent resistors randomly, the dissimilarity between them can reach 23.2%, which cause a bad sun tracking even with initial offset calibration, in the other hand, and by the use of selected LDRs using the test bench, the dissimilarity drops to 0.06%, which meets requirements of solar power concentration systems.</span>

Role of CsMnCl3 Nanocrystal Structure on Its Luminescence Properties

Cesium manganese chloride (CsMnCl3) nanocrystals (NCs) have recently been recognized as potential lead-free perovskite candidates for red emission. To ascertain how the luminescence properties depend on the NC structures formed under different synthesis conditions, we synthesized CsMnCl3 NCs in two polymorphic structures, namely, cubic (c-CsMnCl3) and rhombohedral (r-CsMnCl3), by tuning the reaction temperature of a hot injection route. c-CsMnCl3 NCs are found to be nonemissive, whereas r-CsMnCl3 NCs exhibit red emission at 670 nm with a photoluminescence quantum yield of 40%. Density functional theory calculations reveal an indirect band gap for c-CsMnCl3─the electronic transitions between valence and conduction band edges are prohibited by orbital symmetry and spin. Conversely, r-CsMnCl3 NCs possess a direct band gap. Further, transient absorption measurements suggest self-trapped exciton formation in r-CsMnCl3 NCs, which contributes to their emission characteristics. Our proof-of-concept demonstration of photocurrent generated from the emitting r-CsMnCl3 NCs indicates their suitability for luminescent solar concentrator applications. The findings of this work highlight the importance of understanding structure-luminescence relationship of emerging lead-free perovskites providing design criteria for red-emitting materials.

Numerical and Experimental Investigation of Nanostructure-Based Asymmetric Light Transmission Interfaces for Solar Concentrator Applications

Research in asymmetric light transmission interfaces has been recently gaining traction. While traditionally considered for optical circuitry applications, there is a new interest to use these interfaces in luminescent solar concentrators. Previous studies have shown that applying them to the top surface of a concentrator could mitigate surface losses. This paper presents experimental results for proof-of-concept asymmetric light transmission interfaces that may have potential applications in luminescent solar concentrators. The interfaces and the underneath substrate were created in a single step from polydimethylsiloxane using silicon molds fabricated on <100> wafers via anisotropic wet etching. The resulting structures were pyramidal in shape. Large surface areas of nanostructures repeating at 800 nm, 900 nm, and 1000 nm were tested for backward and forward transmission using a spectrometer. Results showed a 21%, 10%, and 0% average transmissivity difference between the forward and backward directions for each periodicity, respectively. The trends seen experimentally were confirmed numerically via COMSOL simulations.

Giant Stokes shift for charged vacancies in monolayer SnS

We perform first-principles density-functional theory calculations to determine the equilibrium defect structures, formation energies, charge transition levels, and electronic structures of Sn and S vacancies in monolayer SnS. Both Sn and S vacancies exhibit multiple charge transition levels and in-gap defect states, indicating that they may be stable in different charge states depending on the Fermi level in the system. Depending on the charge state of the vacancy, the easily distorted SnS lattice undergoes different relaxations, and in some cases, symmetry-breaking reconstructions, creating defect states within the gap that electrons can occupy at a lower energetic cost. Due to significant atomic relaxations between the equilibrium defect structures in different charge states, optical charge transitions involving both types of vacancies exhibit significant Stokes shifts of over 1 eV, which may provide opportunities for increased efficiency in light emission diode, solar cell, and solar concentrator applications.

The effect of the thickness on structural, optical limiting, and dielectric properties of hybrid coatings rhodamine B dye films on an epoxy polymeric substrate for display applications

Various thickness of Rhodamine B (RhB) laser dye was deposited on epoxy polymeric as a new dielectric organic substrate by spin coating method for the first time. This study focused on the newly considered RhB dye on an epoxy substrate for wide-scale applications. The thickness effect on structural, optical, and dielectric properties of the hybrid coating films was performed. The XRD patterns of the films indicated a large hump amorphous design and lack of Bragg peak intensity associated with the RhB laser dye, due to amorphous film concentration. From UV-Visible spectroscopy, the optical absorption edge shifts to the higher wavelengths direction (redshift) with the variation in RhB dye thicknesses. It was found that the energy band gap decreased when the RhB dye film thickness changed. The refractive index is an important parameter influencing the optical component design. Their values vary according to each relationship that extremely useful the films in optical devices. Laser power attenuation sensitivity of pure epoxy polymeric substrate and its coating films shows that under reducing the thicknesses of RhB dye, the laser power intensity effect increases. Several dielectric parameters are extracted from the series and parallel capacitance measurements. The present results offer new material films for luminescent energy solar concentrator applications.

Hybrid high-concentration photovoltaic-thermal solar systems for building applications

In situ photovoltaic-thermal (PVT) solar energy generation in buildings is an effective way to cover both thermal and electrical energy demands, mimizing losses and costs associated with transportation. High-concentration PVT (HCPVT) collectors present higher electrical conversion efficiencies, lower thermal dependence coefficients and the possibility of achieving higher temperature heat than conventional PVT systems. These features address the need of maximizing the energy generation in cities where there is very limited available space for renewable energy installations. In the present study, a HCPVT module has been designed, modelled and simulated. Simulations have been conducted for two representative cities with different climates but both suitable for solar concentration applications: Almería (Spain) and Lancaster (United States). The results demonstrate a very good performance in both locations, covering from 95% to 100% of the domestic hot water demand, and more than 55% of the space heating and cooling and electricity demands. Additionally, a comparison with a standard PVT solar collector has been carried out, indicating that the HCPVT system clearly outperforms the standard one in terms of the electricity and the thermal energy produced.

Metal-insulator multilayer precursors for enhanced Sm2+ absorption and Tm2+ luminescence in SiAlO thin films prepared by magnetron sputtering

Silicon-aluminum-oxigen (SiAlO) coatings doped with Sm2+ and prepared by reactive magnetron co-sputtering of Si, Al, and Sm targets, are attractive for luminescence solar concentrator applications but suffer from the low absorption between 300 and 600 nm. This article reports that the main cause of low absorption is a high concentration of undesired Sm3+. This finding is supported by optical transmittance, photoluminescence emission and excitation characterization, and X-ray photoelectron spectroscopy data of the Sm's 3d5/2 edge. We present an alternative deposition process for obtaining Sm doped SiAlO layers with enhanced Sm2+ absorption by incorporating Sm through the use of multilayer thin-film precursors composed of metallic Sm and SiAlO layers. After thermal post-deposition treatments, diffusion and reaction of the metallic Sm layers with the SiAlO host results in coatings showing the characteristic 5d → 4f transitions of Sm2+ in the region between 250 and 600 nm which were not detectable in Sm-doped single layers. This same deposition strategy produces Tm doped SiAlO coatings with Tm2+‘s characteristic luminescence at 1132 nm when the SiAlO host is in the mullite composition region. The photoluminescence excitation spectrum of Tm2+ is compared to phosphor with similar composition and covers the range between 300 and 700 nm.

A computational exploration of aggregation-induced excitonic quenching mechanisms for perylene diimide chromophores.

Perylene diimide (PDI) derivatives are widely used materials for luminescent solar concentrator (LSC) applications due to their attractive optical and electronic properties. In this work, we study aggregation-induced exciton quenching pathways in four PDI derivatives with increasing steric bulk, which were previously synthesized. We combine molecular dynamics and quantum chemical methods to simulate the aggregation behavior of chromophores at low concentration and compute their excited state properties. We found that PDIs with small steric bulk are prone to aggregate in a solid state matrix, while those with large steric volume displayed greater tendencies to isolate themselves. We find that for the aggregation class of PDI dimers, the optically accessible excitations are in close energetic proximity to triplet charge transfer (CT) states, thus facilitating inter-system crossing and reducing overall LSC performance. While direct singlet fission pathways appear endothermic, evidence is found for the facilitation of a singlet fission pathway via intermediate CT states. Conversely, the insulation class of PDI does not suffer from aggregation-induced photoluminescence quenching at the concentrations studied here and therefore display high photon output. These findings should aid in the choice of PDI derivatives for various solar applications and suggest further avenues for functionalization and study.

Sm2+-doped SiAlO sputter deposited coatings for self-absorption and scatter-free luminescent solar concentrator applications

Combinatorial reactive co-sputtering using Al, Si and Sm targets in an Ar + O2 atmosphere, resulted in Sm doped SiAlO thin films with a wide Sm concentration- and Si:Al composition gradient. By combining position dependent EDX spectra and laser excited emission spectra, ternary phase diagrams were constructed that directly show the relation between Sm emission intensity, index of refraction, thickness and composition. Using this approach, the Sm2+ and Sm3+ emission intensity ratio was controlled towards films with predominantly Sm2+ emission, which is most favorable for luminescent solar concentrator (LSC) applications. The optimum Sm2+ efficiency was reached when the Al content was about equal to the Sm content. When the Si:Al ratio decreases, the Sm2+ emission intensity strongly drops to almost zero. However, sputtering without Al resulted in no Sm2+ emission intensity at all. The excitation and emission properties of Sm2+ in the optimized thin films, especially the ratio between the 4f→4f and 5d→4f emission that is sensitively susceptible to the co-ordination polyhedron, closely resembles that of Sm2+ doped crystalline powders with the same composition. This strongly suggest that the Sm2+ ions in our amorphous films are coordinated in the same way. A homogeneous thin film on float glass clearly shows the light concentration effect of the red Sm2+ emission. Due to an unexplained low Sm2+ absorption of our films, even the optimized thin films do not luminesce brightly.

Light-intensity and thickness dependent efficiency of planar perovskite solar cells: charge recombinationversusextraction

We reveal the complex interplay between photoactive layer thickness and illumination intensity in perovskite solar cells, presenting design criteria for real-world and solar concentrator applications.

Enhancement of power conversion efficiency of an angular luminescent solar concentrator employing a silica reinforced PMMA:CASN:Eu2+ composite

We report here the optical and electrical properties of an organic–inorganic hybrid polymer composite for Luminescent Solar Concentrator (LSC) applications in an angular orientation. Square composite sheets were fabricated by embedding the phosphor, CASN:Eu2+ at different concentrations in a (poly)-methyl methacrylate (PMMA) matrix reinforced with silica nanoparticles (SiNPs). Here the incorporation of SiNPs facilitate the phosphor dispersion in PMMA and enhance the PL intensity without any shift in the emission wavelength. However, from diffuse reflectance studies, it is confirmed that this enhancement is in effect a consequence of particle scattering occurring near the phoshphor’s emission wavelength in the presence of SiNP. On analysing the edge emission at the phosphor’s excitation wavelength, the composite’s optical density (OD) is found to assist unattenuated wave propagation toward the sheet’s edge with a maximum optical efficiency (ηopt) of 9.94%. Under planar illumination, the maximum power conversion efficiency (PCE) is achieved with the 0.25 wt% composite which is ∼ 50% of the bare mc-Si solar cell. This value is increased exceptionally to about 64% of bare cell efficiency at angular orientation as a result of the light-guiding property of the composite through coherent back scattering.

Characterization of Double-Doped Polymer Optical Fibers as Luminescent Solar Concentrators

This work reports on a diameter dependence analysis of the performance as luminescent solar concentrators of three self-fabricated polymer optical fibers (POFs) doped with a hybrid combination of dopants. The works carried out include the design and self-fabrication of the different diameter fibers; an experimental analysis of the output power, of the output irradiance and of the fluorescent fiber solar concentrator efficiency; a comparison of the experimental results with a theoretical model; a study of the performance of all the fibers under different simulated lighting conditions; and a calculation of the active fiber length of each of the samples, all of them as a function of the fiber core diameter. To the best of our knowledge, this paper reports the first analysis of the influence of the POF diameter for luminescent solar concentration applications. The results obtained offer a general perspective on the optimal design of solar energy concentrating systems based on doped POFs and pave the way for the implementation of cost-effective solar energy concentrating devices.

High performance fluorescent fiber solar concentrators employing double‐doped polymer optical fibers

Novel double-doped polymer optical fibers have been fabricated by a bulk polymerization and fiber drawing process for fluorescent fiber solar concentration applications. Poly(methyl methacrylate) has been used as host material and a combination of organic dyes (Perylene/Lumogen Orange/Coumarin 1/Coumarin 6)) and metalorganic materials (Eu(TTFA)3Phen) have been employed as dopants. A concise polymer analysis has been carried out, and the obtained fibers have been characterized under standard AM 1.5G solar simulator excitation. The output power generated at one of the end surfaces of each of the fibers have been measured for 6cm illuminated fiber length, obtaining a concentrated intensity of 0.31mW/mm2 and a fiber conversion efficiency of 0.41% in the best case. Besides, the performance of the fabricated fibers under different weather scenarios have been studied, showing good response at all the simulated day-conditions. Active fiber lengths of more than 6m have been successfully tested, obtaining output intensities of 1.3mW/mm2. Good performance under constant excitation has also been reported during photostability experiments. The results obtained may have a strong impact in the field of luminescent solar concentrators as they offer a promising cost-effective route to green energy production.

Optimization of Photon and Electron Collection Efficiencies in Silicon Solar Microcells for Use in Concentration‐Based Photovoltaic Systems

AbstractUltrathin silicon solar microcells (μ‐cells) afford a means to reduce semiconductor material consumption and can be integrated with concentration optics to improve their power density. A μ‐cell design is described that optimizes electron and photon collection with enhanced efficiency for solar concentration applications. An interdigitated back contact (IBC) design improves carrier collection partially due to larger contact coverage while further enabling optimization of the μ‐cell front surface. To do so, a silicon nitride antireflection thin film coating is utilized to enhance photon absorption and improve surface passivation. Performance of IBC μ‐cells is compared to an optimized top contact design and improves μ‐cell conversion efficiencies from 9.9 to 13.7%. Improvements at 1 Sun are amplified under concentration and increase power densities at 20 Suns to 346 from 192 mW cm−2 due to minimized series resistance. Benefits afforded by IBC μ‐cells are exemplified following their integration into a dual concentrator system, affording photon collection capacities for direct and diffuse irradiance. A traditional lens concentrates direct light while a luminescent solar concentrator (LSC) collects diffuse photons otherwise not utilized by passive optics. Addition of the LSC increases maximum power densities on clear and cloudy days, providing concentration for the latter and further increasing the power density.

Spectral downshifting in Cr3+-Yb3+-Nd3+ doped Ba-Al metaphosphate glass: Role of Nd3+ as bridging ion

Here, Cr3+ sensitized intense luminescence is obtained from Yb3+ ions in a series of newly formulated Cr-Yb doped Ba-Al metaphosphate glass. It has been observed from measured FTIR and absorption spectra that, Yb3+ ion plays the role of network modifier by polymerizing the network in this host. The Yb3+ emission intensity enhanced significantly under Cr3+ excitation in codoped sample due to Cr3+ to Yb3+ energy transfer which is further increased as a function of Yb3+ concentration up to 1 mol% beyond which decrease of luminescence is observed. The energy transfer from Cr3+ to Yb3+ is further improved on inclusion of Nd3+ ions resulting in slight increase of Yb3+emission intensity. This indicates the role of Nd3+ ions in bridging the energy gap between Cr3+ and Yb3+ is nominal due to significant red shift of Cr3+ emission in this host to bring about effective spectral downshifting which may prove to be useful for production of flash-lamp pumped Yb3+ lasers as well as solar concentrator applications.

Good Dispersion of Large-Stokes-Shift Heterovalent-Doped CdX Quantum Dots into Bulk PMMA Matrix and Their Optical Properties Characterization

Dispersion of quantum dots (QDs) into a PMMA polymer matrix is promising for luminescent solar concentrator applications in improving the application of photovoltaic cells in both efficiency and flexibility. However, some problems like self-absorption of emitted light, drastic agglomeration, and the oxidation of QDs limit the application of it. Herein, we introduced heterovalent-doped CdX (X = S, Se):Ag (Cu) QDs with stable doped luminescence and large Stokes shift prepared by cation exchange strategy into a PMMA matrix, in which such good performances were kept after in situ polymerization. The UV–vis absorption and PL spectra comparison before and after polymerization confirmed this. The FT-IR, 1HNMR, XPS, and TG-DTA characterizations have been used to explore the interaction between QDs and the polymer matrix. The Stokes shift of them after dispersion in PMMA was larger than 0.9 ev, and the absolute quantum yields were more than 50% after dispersed in bulk PMMA. The luminescence collection behavior of the flexibly shaped centimeter-scale PMMA matrix confirmed their promising applications as a luminescent solar concentrator.

Cellulose nanocrystals as host matrix and waveguide materials for recyclable luminescent solar concentrators

We report the use of an ecofriendly and recyclable CNC material as the host matrix for luminescent solar concentrator applications.

Ray-trace simulation of CuInS(Se)₂ quantum dot based luminescent solar concentrators.

To enhance the performance of luminescent solar concentrator (LSC), there is an increased need to search novel emissive materials with broad absorption and large Stokes shifts. I-III-VI colloidal CuInS2 and CuInSe2 based nanocrystals, which exhibit strong photoluminescence emissions in the visible to near infrared region with large Stokes shifts, are expected to improve performance in luminescent solar concentrator applications. In this work, the performance of CuInS(Se)2 quantum dots in simple planar LSC is evaluated by applying Monte-Carlo ray-trace simulation. A systematic parameters study was conducted to optimize the performance. An optimized photon concentration ratio of 0.34 for CuInS2 nanocrystals and 1.25 for CuInSe2 nanocrystals doping LSC are obtained from the simulation. The results demonstrated that CuInSe2 based nanocrystals are particularly interesting for luminescent solar concentrator applications, especially to combine with low price Si solar cells.

Broadband behavior of transmission volume holographic optical elements for solar concentration.

A ray tracing algorithm is developed to analyze the energy performance of transmission and phase volume holographic lenses that operate with broadband illumination. The agreement between the experimental data and the theoretical treatment has been tested. The model has been applied to analyze the optimum recording geometry for solar concentration applications.

Poly(methyl methacrylate) (PMMA) doped with DCJTB for luminescent solar concentrator applications

Poly(methyl methacrylate) (PMMA) doped with various amounts of the organic-dye 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) for luminescent solar concentrator (LSC) applications have been studied. The maximum wavelength of the emission peaks increases from 555 to 561nm as the doped amount of organic-dye DCJTB increases from 2.08 (sample L3) to 8.33mg (sample L5), which reveals a slight red-shift effect. The difference between the maximum wavelengths of the absorption and emission spectra (λs) decreases from 58 to 47nm as the doped amount of organic-dye DCJTB increases from 2.08 to 8.33mg, which shows the Stokes shift. The short circuit photocurrent (Isc) increases from 11.68 to 14.11mA/cm2 as the doped amount of organic-dye DCJTB increases from 0 (undoped, sample L0) to 8.33mg. The optical efficiency (ηopt) also increases from 41.67% to 60.00% as the doped amount of organic-dye DCJTB increases. The maximum value of the incident photon-to-current conversion efficiency (IPCE) was about 9.0% at 526nm when doped with 8.33mg of organic-dye DCJTB (sample L5). The results of the present paper show through a well-conducted study on the optical properties of PMMA doped with organic-dye DCJTB that it can be suitable for LSC applications.