Luminescent Solar Concentrators Research Articles

Enhanced Lifetime of Cyanine Salts in Dilute Matrix Luminescent Solar Concentrators via Counterion Tuning.

Organic luminophores offer great potential for energy harvesting and light emission due to tunable spectral properties, strong luminescence, high solubility, and excellent wavelength-selectivity. To realize their full potential, the lifetimes of luminophores must extend to many years under illumination. Many organic luminophores, however, have a tendency to degrade and undergo rapid photobleaching, leading to the perception of intrinsic instability of organic molecules. In this work we demonstrate that by exchanging the counterion of a heptamethine cyanine salt the photostability and corresponding lifetime of dilute cyanine salts can be enhanced by orders of magnitude from 10 hours to an extrapolated lifetime of greater than 65,000 hours under illumination. To help correlate and comprehend the underlying mechanism behind this phenomenon, the water contact angle and binding energy of each pairing were measured and calculated. We find that increased water contact angle, and therefore increasing hydrophobicity, generally correlate to improved lifetimes. Similarly, a lower absolute binding energy between cation and anion correlates to increased lifetimes. Utilizing the binding energy formalism, we predict the stability of a new anion and experimentally verify with good consistency. Moving forward, these factors could be used to rapidly screen and identify highly photostable organic luminophore salt systems for a range of energy harvesting and light emitting applications.

Luminescent solar concentrator efficiency versus edge solar cell coverage.

This Letter introduces an analytical approach to estimate the waveguiding efficiency of large-area luminescent solar concentrators (LSCs), where the edges are covered by a varied number of mirrors and solar cells. The model provides physically relevant description in the whole range of optical (absorption, scattering) and geometrical (size) parameters of rectangular LSCs. A 19 × 19cm2 silicon quantum dot-based LSC has been fabricated to verify the theory. Within an experimental error, the predicted waveguiding efficiency matched well the measured one. A critical LSC size, beyond which a part of the device turns inactive, has been determined as N/α for N attached solar cells (one or two) and LSC material absorption coefficient α. This model provides a straightforward waveguiding analysis tool for large-area LSCs with different structural parameters relevant for both high concentration ratio and glazing applications.

Environmental Effects on the Performance of Quantum Dot Luminescent Solar Concentrators.

Luminescent solar concentrators (LSCs) are all-photonic, semitransparent solar devices with great potential in the emerging fields of building-integrated photovoltaics and agrivoltaics. Over the past decade, particularly with the advent of quantum dot (QD) LSCs, tremendous progress has been made in terms of photovoltaic efficiency and device size by increasing solar spectral coverage and suppressing reabsorption losses. Despite these advances in LSC design, the effects of environmental conditions such as rain, dust, and dirt deposits, which are ubiquitous in both urban and agricultural environments, on LSC performance have been largely overlooked. Here, we address these issues by systematically investigating the environmental effects on the solar harvesting and waveguiding capability of state-of-the-art QD-LSCs, namely, the presence of airborne pollutants (dust), water droplets, and dried deposits. Our results show that dust is unexpectedly insignificant for the waveguiding of the concentrated luminescence and only reduces the LSC efficiency through a shadowing effect when deposited on the outer surface, while dust accumulation on the inner LSC side increases the output power due to backscattering of transmitted sunlight. Water droplets, on the other hand, do not dim the incident sunlight, but are detrimental to waveguiding by forming an optical interface with the LSC. Finally, dried deposits, which mimic the evaporation residues of heavy rain or humidity, have the worst effect of all, combining shading and waveguide losses. These results are relevant for the design of application-specific surface functionalization/protection strategies real LSC modules.

Luminescent Solar Concentrators with Dual Functions of Photovoltaic and Piezoelectric Properties for Wireless Self‐Powered Speed Measurement

AbstractThe solar‐only response nature limits the luminescent solar concentrators (LSCs) to solar harvesting rather than responding to other stimuli, which restricts the role of LSCs to energy supply in self‐powered internet of things (IoT) systems, and the application potential of LSCs in self‐powered devices has been seriously overlooked. In this work, LSCs with photovoltaic and piezoelectric features are proposed for the first time, extending the application scenario of LSCs to self‐powered sensors with pressure responsiveness. The luminescent layer of perovskite‐polymer composite film is prepared via in situ blade coating with the piezoelectric polymer matrix of poly(vinylidenefluoride‐trifluoroethylene) (P(VDF‐TrFE)). P(VDF‐TrFE) possesses stronger DMF adsorption capacity and higher electroactive phase content than a conventional piezoelectric matrix of poly(vinylidene fluoride) (PVDF), which not only reduces the residual‐solvent‐induced defects in perovskite luminophores, but also brings a sensitive pressure response to LSCs. The dual‐functional LSCs achieve a power conversion efficiency of 1.01% and a output piezoelectric voltage of 0.95 V can be obtained even at a low pressure of 0.16 kPa. A self‐powered speed measurement system is demonstrated, and the actual speed measurement is carried out. Such dual‐functional LSCs show great potential in self‐powered electrical devices, which can be applied to low‐energy‐consumption IoT systems and other commercial smart home products.

Spatially Resolved Optical Efficiency Measurements of Luminescent Solar Concentrators.

Luminescent solar concentrators (LSCs) are able to concentrate both direct and diffuse solar radiation, and this ability has led to great interest in using them to improve solar energy capture when coupled to traditional photovoltaics (PV). In principle, a large-area LSC could concentrate light onto a much smaller area of PV, thus reducing costs or enabling new architectures. However, LSCs suffer from various optical losses which are hard to quantify using simple measurements of power conversion efficiency. Here, we show that spatially resolved photoluminescence quantum efficiency measurements on large-area LSCs can be used to resolve various loss processes such as out-coupling, self-absorption via emitters, and self-absorption from the LSC matrix. Further, these measurements allow for the extrapolation of device performance to arbitrarily large LSCs. Our results provide insight into the optimization of optical properties and guide the design of future LSCs for improved solar energy capture.

A Mechanoresponsive Smart Window Based on Multifunctional Luminescent Solar Concentrator

A novel approach to creating a multifunctional smart window that combines electricity generation with transparency modulation is developed. The proposed smart window is based on a mechanoresponsive luminescent solar concentrator (LSC) composed of organic fluorophores (coumarin 6) impregnated into a compressible polymer matrix (polydimethylsiloxane, PDMS) that is surface‐modified on one side. In its initial state, the LSC is optically transparent but becomes increasingly opaque upon the application of compressive strain to the PDMS matrix, resulting in a higher optical shielding property and eventually becoming translucent. The smart window's degree of specular transmission can be reversibly adjusted between 20% and 84%, making it suitable for use as a switchable privacy window. Additionally, the LSC‐photovoltaic (PV) window maintains a high power conversion efficiency (PCE) even when in a translucent state with the privacy function enabled. Under AM1.5G solar irradiation (1 sun, 100 mW cm2), the LSC‐PV module achieves PCEs of 1.05–1.48% and optical efficiencies (ηopt) of 8.6–12.0%, depending on the strain. This technology holds significant promise for building‐integrated photovoltaics and smart window applications, such as privacy‐protecting windows, daylight‐controlling windows, power‐generating antinoise barriers, and transparent solar cells.

Quantifying Mie Scattering in Luminescent Solar Concentrators for Improved Performance

Quantifying Mie Scattering in Luminescent Solar Concentrators for Improved Performance

High-loading of organosilane-grafted carbon dots in high-performance luminescent solar concentrators with ultrahigh transparency

Carbon dots (CDs) generally suffer from aggregation-induced fluorescence quenching effect in solid-state, which significantly limits their application in photoelectric devices. Due to this effect, it is a great challenge to achieve high-transparency and high-performance luminescent solar concentrators (LSCs) based on CDs. Here, the synthesis of organosilane-grafted carbon dots (Si-CDs) is rationally designed by hydrothermal method using anhydrous citric acid, ethanolamine and KH-792 as the reaction precursors. The obtained Si-CDs can be uniformly dispersed in the polyvinyl alcohol (PVA) matrix through the dehydration condensation reaction and hydrogen bonding between the silicon hydroxyl group of Si-CDs and the hydroxyl group of PVA. Based on this property, Si-CDs/PVA thin-film LSCs (5 ×5 ×0.2 cm3) with ultrahigh CD loading (25 wt%) and high transparency can be fabricated, exhibiting excellent absorption in the UV spectral region and about 90 % transmission in the visible range. Furthermore, the power conversion efficiency (PCE) of the LSCs can reach 2.09 % under a standard solar light and shows excellent stability even over 12 weeks. This synthetic design is expected to be beneficial for future development of CD synthesis and paves the way for the development of CDs-based photoelectric devices.

Design of more efficient luminescent solar concentrators by using peripherally dye-doped stacked optical fibers.

Ways of improving the optical efficiency of luminescent solar concentrators based on multiple poly(methyl methacrylate) plastic optical fibers peripherally doped with two promising types of dyes are analyzed by means of a Monte-Carlo computational model developed by us. By comparing the performance of optical fibers doped with lumogen red and lumogen yellow, or combinations of them at several concentrations, this work clarifies how to achieve a better compromise between the trapping efficiency of the sunlight and the reabsorption of the light emitted by the mixture in stacked optical fibers connected to a photovoltaic solar cell.

Towards a luminescent solar concentrator with ultra-broadband absorption and spectral conversion for optimizing photovoltaic solar cell response: “The photonic cannon shot”

Solar energy harvesting is largely limited by the spectral sensitivity of the employed photovoltaic solar cell, since typically the full potential of each photon of the whole solar spectrum is not efficiently used in the generation of electricity. Therefore, increasing the overall solar spectrum utilization is of crucial interest and stands up as a frontier-of-research approach in the photovoltaic sector. Here we present an innovative ultra-broadband absorption and multiple spectral conversion approach, by means of rare-earth doped materials together with organic dyes embedded in a luminescent solar concentrator. The combination of different luminescent materials is a key factor for improving energy harvesting over the whole solar spectrum. At the same time, a simultaneously combined effect of up-conversion and down-shifting of light is aimed to optimal spectral matching with amorphous silicon solar cells response. Thus, UV–visible photons coming from the incoming sunlight, together with UV–visible up-converted photons coming from near-infrared radiation, can be all shifted to the yellow-orange-red part of the spectrum. To the best of our knowledge, this represents the first reported proof-of-concept using LSCs with up-conversion and down-shifting photonic processes working together and sequentially.

Coherent heteroepitaxial growth of I-III-VI2 Ag(In,Ga)S2 colloidal nanocrystals with near-unity quantum yield for use in luminescent solar concentrators

Colloidal Ag(In,Ga)S2 nanocrystals (AIGS NCs) with the band gap tunability by their size and composition within visible range have garnered surging interest. High absorption cross-section and narrow emission linewidth of AIGS NCs make them ideally suited to address the challenges of Cd-free NCs in wide-ranging photonic applications. However, AIGS NCs have shown relatively underwhelming photoluminescence quantum yield (PL QY) to date, primarily because coherent heteroepitaxy has not been realized. Here, we report the heteroepitaxy for AIGS-AgGaS2 (AIGS-AGS) core-shell NCs bearing near-unity PL QYs in almost full visible range (460 to 620 nm) and enhanced photochemical stability. Key to the successful growth of AIGS-AGS NCs is the use of the Ag-S-Ga(OA)2 complex, which complements the reactivities among cations for both homogeneous AIGS cores in various compositions and uniform AGS shell growth. The heteroepitaxy between AIGS and AGS results in the Type I heterojunction that effectively confines charge carriers within the emissive core without optically active interfacial defects. AIGS-AGS NCs show higher extinction coefficient and narrower spectral linewidth compared to state-of-the-art heavy metal-free NCs, prompting their immediate use in practicable applications including displays and luminescent solar concentrators (LSCs).

Leaf-inspired luminescent solar concentrator based on two-stage photoconversion.

Geometrical gain of a luminescent solar concentrator is drastically increased by laying out a luminescent fiber in a luminescent plate with air gap around it and attaching a photovoltaic (PV) cell to the tip of the fiber. The plate converts an incident photon to a first photoluminescence (PL) photon, and the fiber converts it to a second PL photon. Thus, the fiber carries the optical power as a leaf vein transports water and nutrients. The probability of the first PL photon resulting in the second PL photon reaching the PV cell can be measured by exciting a single spot on the plate with a laser beam. In experiment, 2 mm-thick, 50 mm-square and 50 mm-diameter circular devices were assembled with off-the-shelf components. For each case, geometrical gain exceeded 1000 and this probability averaged over the incident area was of the order of 0.01. Connecting multiple small-area devices to a single PV cell with a clear fiber would increase geometrical gain further and alleviate the absorption and scattering of PL photons during waveguiding.

Energy and Thermal Performance Analysis of Quantum Dot Luminescent Solar Concentrators in Greenhouses

AbstractGreenhouses provide a controlled environment for plant growth, which increases crop yields, reduces the use of water and fertilizers, and offers resilience to droughts and extreme weather. However, greenhouse operation is energy intensive due to their heating and cooling loads. Luminescent solar concentrators (LSCs) are promising for semitransparent greenhouse roofs that produce clean electricity, thus reducing the greenhouse energy demand, while also transmitting enough light to satisfy plant growth. Herein, we model the performance of LSC roofs designed as glass panels coated with quantum dot (QD)/polymer nanocomposite films and front‐facing surface‐mounted photovolatic cells. Five widely studied QD materials are examined to demonstrate that the proposed QD LSC roofs can have effective power conversion efficiencies exceeding 10% while also increasing the red‐light fraction, which is beneficial for plant growth. The effect of LSC integration on the greenhouse thermal energy demands is studied for the example of silicon (Si) QD LSC roofs. In warm climates, solar power generated by the Si QD LSC roofs satisfies the entire greenhouse energy demand and thus enables net‐zero energy operation. Overall, the results of the current research demonstrate the strong potential of integrating QD LSCs into greenhouses to reduce energy costs and enhance plant growth.

Design of a Ventilated Façade Integrating a Luminescent Solar Concentrator Photovoltaic Panel

The increasing trend towards decarbonization requires the reduction of the environmental impact of the building sector that currently accounts for approximately 40% of the total CO2 emissions of European countries. Even though Luminescent Solar Concentrator (LSC) panels could be a very promising technology to be installed in urban environments, there is still little implementation of LSC panels in building façades. Here, the realization of a Ventilated Façade (VF) integrating an LSC device as an external pane is presented and a preliminary numerical and experimental investigation is used to evaluate the interaction between the different structure components. Thanks to the realization of a dedicated mock-up finite element method, models are calibrated and validated against experimental measurements, showing a good correspondence between simulated and measured data. Moreover, the electrical characterization of the LSC panel confirms that large area devices can be used as an external skin of VF, reporting a photovoltaic efficiency of 0.5%. The system’s thermal and optical properties (estimated thanks to the software COMSOL Multiphysics) encourage the continuation of the research by considering different technologies for the VF internal skin, by scaling up the case study, and by running the simulation of an entire building considering winter and summer energy demands.

Initiation and recovery of damage initiated by UV irradiation in luminescent solar concentrators deposited in ambient conditions

Photopolymerization of thin, dye-doped acrylate-based layers under ambient conditions often requires high concentrations of photoinitiators. The radical storm created during polymerization has been shown to cause damage to the embedded fluorescent dyes; some of this damage is repaired upon exposure to air, but a fraction of the damaged molecules do not repair. This work presents a more detailed optical study of the environmental effects, nature of the initiator, and resulting fluorescence of the dye molecules caused by photopolymerization, all factors necessary to understand and control to allow ambient inkjet printing of these luminescent species.

Ray-Trace Modeling to Characterize Efficiency of Unconventional Luminescent Solar Concentrator Geometries.

Luminescent solar concentrators (LSCs) are a promising technology to help integrate solar cells into the built environment, as they are colorful, semitransparent, and can collect diffuse light. While LSCs have traditionally been cuboidal, in recent years, a variety of unconventional geometries have arisen, for example, circular, curved, polygonal, wedged, and leaf-shaped designs. These new designs can help reduce optical losses, facilitate incorporation into the built environment, or unlock new applications. However, as fabrication of complex geometries can be time- and resource-intensive, the ability to simulate the expected LSC performance prior to production would be highly advantageous. While a variety of software exists to model LSCs, it either cannot be applied to unconventional geometries, is not open-source, or is not tractable for most users. Therefore, here we introduce a significant upgrade of the widely used Monte Carlo ray-trace software pvtrace to include: (i) the capability to characterize unconventional geometries and improved relevance to standard measurement configurations; (ii) increased computational efficiency; and (iii) a graphical user interface (GUI) for ease-of-use. We first test these new features against data from the literature as well as experimental results from in-house fabricated LSCs, with agreement within 1% obtained for the simulated versus measured external photon efficiency. We then demonstrate the broad applicability of pvtrace by simulating 20 different unconventional geometries, including a variety of different shapes and manufacturing techniques. We show that pvtrace can be used to predict the optical efficiency of 3D-printed devices. The more versatile and accessible computational workflow afforded by our new features, coupled with 3D-printed prototypes, will enable rapid screening of more intricate LSC architectures, while reducing experimental waste. Our goal is that this accelerates sustainability-driven design in the LSC field, leading to higher optical efficiency or increased utility.

Cesium Copper Halide Perovskite Nanocrystal-Based Photon-Managing Devices for Enhanced Ultraviolet Photon Harvesting.

Space-based solar power harvesting systems with high levels of specific power (the power produced per mass of the mounted photovoltaic cell) are highly desired. In this study, we synthesized high quality lead-free Cs3Cu2Cl5 perovskite nanodisks with efficient ultraviolet (UV) photon absorption, high photoluminescence quantum yields, and a large Stokes shift, which are suitable to serve as photon energy downshifting emitters in the applications of photon-managing devices especially for space solar power harvesting. To demonstrate this possibility, we have fabricated two types of photon-managing devices, i.e., luminescent solar concentrators (LSCs) and luminescent downshifting (LDS) layers. Both experimental results and simulation analyses show that the fabricated LSC and LDS devices exhibit high visible light transmission, low photon scattering and reabsorption energy loss, high UV photon harvesting, and energy conversion after integrating with silicon-based photovoltaic cells. Our research presents a new avenue for utilizing lead-free perovskite nanomaterials in space applications.

A perspective on the use of perovskite luminophores for solar windows

Perovskite (PRV) luminescent solar concentrators (LSCs) use PRV materials to concentrate and convert sunlight into electricity. LSCs are made up of a flat plate or sheet of glass or plastic that contains a layer of luminescent PRV material. When sunlight enters the LSC, the PRV material absorbs the light and emits it at a longer wavelength. This emitted light is then trapped inside the LSC by total internal reflection, and it travels to the edges of the plate where it is collected by photovoltaic (PV) solar cells (SCs). The use of PRV materials in LSCs offers several advantages over other materials. PRV materials are highly efficient at converting light into electricity. They are also flexible, low-cost, and easy to manufacture, making them a promising candidate for large-scale solar energy applications. However, PRV materials have some challenges preventing their adoption. They are sensitive to moisture or heat and can degrade quickly over time. This significantly limits their lifespan and stability. Research on PRV is mostly focused on making them more stable and durable, but finding ways to improve the manufacturing process to reduce costs and increase efficiency is also relevant. While the opportunities offered by PRV materials for the specific application to LCSs are certainly interesting, the challenges make the prospect of a commercial product very unlikely in the short term.

Thin film luminescent solar concentrators fabricated for indoor applications

The luminescent solar concentrators are considered a promising photovoltaic solution to improve the energy efficiency of building structures. The main role of these devices is to provide a novel route for harnessing solar radiation with designs in the form of semi-transparent glazing systems that could be used for building-integrated photovoltaic system or interior furniture components. Herein, we reported the fabrication and characterization of thin-film LSC devices formed with different lightguides containing Eosin Y, Safranin O dyes and the two-dye mixture. Under indoor illumination condition, the two-dye mixture LSC has a power conversion efficiency of 0.22%, which is greater than that of the single-dye LSCs. Moreover, the dependency of external solar parameters on incident light power are investigated. The data indicate that the dependency is best described with the two-dye mixture. Ultimately, this study might guide the studies to expand the use of the two-dye mixture thin film LSC devices for indoor applications.

High-efficiency plasmonic luminescent solar concentrators based on thiol-ene polymer

Advances in solar energy harvesting technology require innovative approaches to meet the growing energy demand. In this work, we exploit the plasmonic interaction of metal nanoparticles with fluorophores to improve the optical performance of luminescent solar concentrators (LSCs). The plasmonic luminescent solar concentrators (PLSCs) with dimensions of 5 cm × 5 cm × 0.5 cm containing CsPbBr3 quantum dots (QDs) and gold nanoparticles (Au NPs) are fabricated, characterized, and evaluated systematically. As the Au NPs concentration increases, the optical performance of PLSCs exhibits, first enhancement, and then diminishment. When the Au NPs concentration is 2 × 10−4 wt%, the optimal external quantum efficiency, optical conversion efficiency, and power conversion efficiency of the PLSC reach 1.58%, 2.90%, and 0.437%, respectively. At higher concentrations of Au NPs, the non-radiative energy transfer from the CsPbBr3 QDs to the Au NPs leads to a decrease of the emission, which can be confirmed by the decreasing lifetime of the QDs. The overall optical performance of PLSCs depends on two competing effects, excitation rate and non-radiative energy transfer efficiency. Furthermore, the PLSC demonstrate the good aesthetic quality as an excellent substitute for commercial glass. We anticipate that the high optical conversion efficiency of PLSCs based on thiol-ene polymer would shed light on future application in LSCs.