Luminescent Solar Concentrators Devices Research Articles

Semi-Transparent Luminescent Solar Concentrators Based on Intramolecular Energy Transfer in Polyurethane Matrices.

Luminescent solar concentrators (LSCs) are spectral conversion devices offering interesting opportunities for the integration of photovoltaics into the built environment and portable systems. The Förster-resonance energy transfer (FRET) process can boost the optical response of LSCs by reducing energy losses typically associated to non-radiative processes occurring within the device under operation. In this work, a new class of FRET-based thin-film LSC devices is presented, in which the synthetic versatility of linear polyurethanes (PU) is exploited to control the photophysical properties and the device performance of the resulting LSCs. A series of luminescent linear PUs are synthesized in the presence of two novel bis-hydroxyl-functionalized luminophores of suitable optical properties, used as chain extenders during the step-growth polyaddition reaction for the formation of the linear macromolecular network. By synthetically tuning their composition, the obtained luminescent PUs can achieve a high energy transfer efficiency (≈90%) between the covalently linked luminophores. The corresponding LSC devices exhibit excellent photonic response, with external and internal photon efficiencies as high as ≈4% and ≈37%, respectively. Furthermore, their optimized power conversion efficiency combined with their enhanced average visible-light transmittance highlight their suitability for potential use as transparent solar energy devices.

Green Light‐Responsive D‐π‐A‐π‐D Quinoxaline Emitters for Luminescent Solar Concentrators: Potential Integration in Agrivoltaic Systems

the integration of photovoltaic technologies within agricultural settings, also known as agrivoltaic, is attracting increasing attention as a sustainable approach to ensure both clean energy and food supply. The success of this strategy relies on the development of innovative materials that can selectively convert specific wavelengths into energy while being transparent to photosynthetically relevant light. To this aim, here we report our endeavors in the synthesis of a new class of D‐π‐A‐π‐D quinoxaline fluorophores and their use in the preparation of wavelength‐selective luminescent solar concentrators (LSC). The dyes were expeditiously prepared following a direct arylation protocol and extensively characterized by spectroscopic analyses and computational studies. They present high light harvesting ability in the green region of the visible spectrum and good emission properties, which were fully retained in the solid state when embedded into a PMMA matrix. These materials were employed to construct LSC devices of promising efficiency, fostering further developments for the use of wavelength‐selective LSC in agrivoltaic systems.

A Multistate Thermoresponsive Smart Window Based on a Multifunctional Luminescent Solar Concentrator.

Conventional luminescent solar concentrators (LSCs) usually only have the ability to absorb solar energy and convert it to electricity but are not able to regulate the transmitted light. Herein, a multistate thermoresponsive smart window (SW) based on LSC has been fabricated, in which the stimuli-responsive host layer consists of polydimethylsiloxane (PDMS) and ethylene glycol solution (EGS) microdroplets stacking with LSC layer-based on near-infrared (NIR) CuInSe2-xSx/ZnS core/shell quantum dots (QDs) and PDMS matrix. As-synthesized CISSe/ZnS QDs with broad NIR absorption in LSC exhibit controllable emission spectra over 833-1088 nm and high photoluminescence (PL) quantum yield from 45 to 83%. Coupling with Si solar cells as a reference, optimized LSC-SW devices with dimensions of 5 × 5 × 0.9 cm3 exhibit higher power conversion efficiency (PCE) of 1.19-1.36% with increased temperature from 0 to 50 °C than those of sole LSC and SW devices. The corresponding visible light transmissions are regulated from 75.1 to 48.1% accordingly. The improvement of PCEs in an opaque state is mainly due to enhanced absorption of QDs originating from rescattered photons from the EGS/PDMS layer, leading to more emitted photons reaching photovoltaics. This work is expected to bring up new opportunities for applications in greenhouses, building facades, and energy-efficient smart windows.

Fabrication and comprehensive investigations on NBD-based luminescent solar concentrator

The design and development of innovative chromophoric materials for luminescent solar concentrators (LSCs) is an emerging area of research in the pursuit of low-cost photovoltaic technology. In this study, we devised and developed the optically active fluorescent dye NBDNH2 based on the skeleton of a benzoxadiazole. In NBDNH2, the electron donating amino group and the electron-withdrawing nitro group are the responsible for intramolecular charge transfer transition as well as fluorescence upon photoexcitation. The structural and photophysical properties of NBDNH2 dye have been meticulously investigated. In addition, the solvent-property relationships also investigated through time-resolved fluorescence and 1H NMR measurements. The photophysical studies reveal that the dye has a moderate Stokes shift, a long fluorescence lifetime and provides guidance for the development of LSCs. NBDNH2 was doped in polymethyl methacrylate (PMMA) to fabricate LSC devices. Due to promising optical properties, the NBDNH2 based LSC (5 × 5 × 0.3 cm3) showed the internal and external photon efficiencies as high as 29.4 % and 3.84 %, respectively. When connected with the photovoltaic cell, the champion device yielded power conversion efficiency of 1.32 % and 0.64 % with scattering and black background, respectively. Based on the findings, we unequivocally envisaged that the benzoxadiazole-based ICT probe is a prospective optical material for LSC applications.

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.

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.

Color-tunable multilayered laminated luminescent solar concentrators based on colloidal quantum dots

Luminescent solar concentrators (LSC) are a promising technology for building integrated photovoltaics (BIPV). Besides obtaining satisfactory efficiencies and aesthetic appeal, a simple and low-cost fabrication process is required to deploy large-scale LSCs. Herein, we introduced a facile and cost-effective fabrication method to obtain laminated LSC (L-LSC) devices. By optimizing the fabrication parameters, L-LSC based on polymer substrates exhibited higher efficiency (power conversion efficiency, PCE=0.24%, external photon efficiency, ηext=4.14% and optical efficiency, ηopt=3.46%) compared to glass-based L-LSC (PCE=0.09%, ηext=1.59%, ηopt=1.76%) due to their excellent optical properties and good compatibility with the laminated emissive layer. Using the optimized L-LSC device, a color-tunable multilayered L-LSC structure is then proposed. By embedding different QDs into two interlayers, the color appearance of the device can be tuned, simultaneously improving the overall efficiency. This study presents a notable advancement towards a practical application of L-LSCs with a satisfactory efficiency and color aesthetics for sustainable BIPVs.

Design, fabrication and preliminary testing of plasmonic luminescent solar concentrator devices

This paper details the design process, fabrication, optimisation and early-stage performance testing of Luminescent and Plasmonic Luminescent Solar Concentrator (LSC & PLSC) devices. A PLSC is a novel approach to solar concentrator technologies that utilizes the principles of luminescence and plasmonics to enhance the devices' solar energy conversion efficiency. This research analyses various mould dimensions, materials and lightguide fabrication methodologies to ensure equivalent LSC/PLSC devices were created in a reproducible method. The optimisation was an iterative process throughout the production and testing stages after which a 100 × 100 × 5 mm PLSC was identified as the optimal for a rooftop installation. To ensure consistency in production as well as assessing the practicality of PLSC installations for building integration, performance testing has been conducted in both indoor and outdoor environments. Additionally, the lifespan of the devices are currently being investigated through ongoing performance evaluations. The incorporation of a reflective backplate has resulted in device efficiency improvements between 14–18% during indoor tests and was consequently included for all devices during outdoor performance analysis. Power conversion efficiencies of 2.3% and 1.7% have been recorded in sub-optimal conditions as well as concentration ratios of 11 and 9 for the PLSC and LSC devices respectively.

Introducing luminescent solar waveguides for sustainable buildings for enhanced circadian rhythm regulation

As the world strives towards a low-carbon future, nearly-zero energy buildings (NZEB) have been the goal to reduce carbon emissions. Artificial lighting is estimated to consume as high as 40% of the total energy consumption in a commercial building. By utilising daylighting, which is the practice of allowing natural light into a building, energy consumption by artificial lighting can be reduced. Luminescent solar concentrators (LSCs) can act as a collector and waveguide to transport outdoor light into the building through total internal reflection. Besides, LSCs absorb a part of the solar spectrum and shift them to different wavelengths through up-conversion or down-conversion. Thus, the output spectrum can be manipulated for the desired indoor applications. Circadian rhythm is the periodic variations in behaviour that follows a 24-hour cycle, which is mainly regulated by light response. A regulated circadian rhythm is important for a healthy life, whereas a disturbed circadian rhythm can lead to health issues such as insomnia and mood disorders. There has been a consensus that our circadian rhythm strongly responds to shorter wavelength light, corroborated in studies. Thus, manipulating the output light of LSCs to contain larger proportions of light with shorter wavelengths could enhance circadian regulation. LSC devices have the potential to transport sufficient daylight up to 5m deep into the building, achieving areas beyond the reach of windows. Thus, LSCs can serve as a tool for daylighting purposes, regulating circadian rhythm and providing sufficient light for comfortable indoor visibility.

Universal measure of photon collection efficiency of dye luminescent solar concentrators

Luminescent solar concentrators (LSC) are recently getting attention as promising components for use in building integrated photovoltaics (BIPV). Ongoing efforts to reduce their optical losses result in active search for new luminophores with large Stokes shift in order to reduce the reabsorption probability. Here we present a novel figure of merit for a large group of Gaussian dye luminophores that provides an accurate assessment of optical losses. Our approach originates in simplified analytical solution for spectral overlapping integral of absorption/emission bands and results in assessment of average reabsorption probability. The procedure is then generalized for any Gaussian dye LSC, by considering its basic parameters (Stokes shift, absorbance and size), thus resulting in a simple useful tool for designing practical LSC devices. Calculations are correlated with the experimental results of reabsorption probability obtained by measuring edge fluorescence spectra of various LSCs. • Width of gaussian spectral bands of molecules is related to Stokes shift. • Their relation enables prediction of reabsorption losses based on Stokes shift. • We numerically derive universally valid expression for losses of Gaussian dye LSCs. • Experiments on selected dye LSCs confirms the validity of our theoretical approach.

Boosting the efficiency of luminescent solar concentrator devices based on CH3NH3PbBr3 perovskite quantum dots via geometrical parameter engineering and plasmonic coupling

In this paper luminescent solar concentrators (LSCs) based on CH 3 NH 3 PbBr 3 perovskite quantum dots (QDs) and QDs containing gold nanoparticles (NPs) with flat and half-cylindrical geometries are introduced. Excitonic and PL emission peaks at 512 nm and 539 nm with majority average size of 16 nm are the characteristics of the synthesized lead bromide perovskite QDs. Incorporation of synthesized spherical gold NPs with an average diameter of 13 nm and absorption peak at 527 nm in perovskite based LSCs are also investigated. The measured reabsorption loss is decreased for LSCs in the presence of gold NPs. The PCE of edge-mounted solar panel in sheet LSCs based on gold NPs doped QDs, is enhanced with respect to CH 3 NH 3 PbBr 3 QD based LSCs, due to plasmonic effect of gold NPs. Varying the LSC geometry to half-cylinder improves the device performance by effectively concentrating of incident light into the solar panel. The effect of backscatterers is also investigated for bottom-mounted solar panel in new half-cylindrical geometry. The best device efficiency is obtained for the white backgrounded LSC, since it could act as a scatter to send back the lost light into the LSC, efficiently. • Lead bromide based Luminescent solar concentrators (LSCs) are fabricated in flat sheet and novel half-cylindrical geometries. • Doping Au NPs to perovskite QDs decreases the reabsorption and boosts the overall output power of LSC devices. • The PCE of half-cylindrical LSC devices are higher than sheet LSCs, due to the lens-like behavior of half-cylinders. • The white back scatterer improves the efficiency of half-cylindrical LSC devices more than mirror and black scatterers.

Color balanced transparent luminescent solar concentrator based on a polydimethylsiloxane polymer waveguide with coexisting polar and non-polar fluorescent dyes.

Color balance is a critical concept in the application of functional transparent polymers from a customer's standpoint. In this study, multiple polar and non-polar fluorescent dyes are embedded simultaneously for the first time in a polydimethylsiloxane (PDMS) polymer matrix. Five dyes successfully coexist with the optimum blending ratio. Furthermore, simultaneous dispersing of polar and non-polar dyes in the polymer is achieved. Absorption and photoluminescence characteristics of multiple fluorescent dyes in PDMS medium are systemically deconvoluted and discussed. The competitive average visible transmittance and color balance of synthesized multi-fluorescent dye embedded PDMS is demonstrated by high color rendering index and CIE color space coordinates close to the white point. Additionally, the luminescent solar concentrator device demonstrates improved power conversion efficiency and light utilization efficiency than the pure PDMS waveguide-based device. Moreover, the long-term storage stability is demonstrated successfully. The findings, therefore, demonstrate the applicability of multi-fluorescent dye embedded PDMS to advanced transparent devices.

Optical center of a luminescent solar concentrator.

This Letter introduces a novel, to the best of our knowledge, approach to estimate the power conversion efficiency (PCE) of a square luminescent solar concentrator (LSC) by point excitations on the "optical centers." Predicted by theoretical calculations, photoluminescence emissions from these optical centers experience almost the same average optical path as those from the whole device under uniform illumination. This is experimentally verified by a 20 × 20 cm2 silicon quantum dot-based LSC, with a negligible error between the predicted PCE and the measured one. This method provides a convenient way to estimate the photovoltaic performance of large-area LSC devices with basic laboratory instruments.

Quantum Dot-based Luminescent Solar Concentrators Fabricated through the Ultrasonic Spray-Coating Method.

Luminescent solar concentrators (LSCs) are a class of wave-guiding devices that can harvest solar light and concentrate it to targeted smaller areas. When coupled with photovoltaic devices (PVs), LSCs hold the potential to be integrated into various application setups, especially for building facade integration toward net-zero-energy buildings. Developing reliable LSC fabrication methods with easy scalability, high adaptability, and device controllability has been an important research topic. In this work, we report an ultrasonic nebulization-assisted spray deposition technique to fabricate quantum dot (QD)-based LSCs (QD-LSCs). This method allows for the production of high-performance QD-LSCs with different device dimensions and geometries. In addition, the quality of the QD thin-film coating layer is relatively independent of the concentration and volume of the coating QD ink solution, allowing for deliberate programming and performance optimization of the resulting QD-LSC devices. We anticipate that this ultrasonic spray coating method can be widely applied to the manufacturing of high-quality LSC devices that are integrable to various applications.

Minimizing Scaling Losses in High-Performance Quantum Dot Luminescent Solar Concentrators for Large-Area Solar Windows.

While luminescent solar concentrators (LSCs) have been researched for several decades, there is still a lack of commercially available systems, mostly due to scalability, performance, aesthetics, or some combination of these challenges. These obstacles can be overcome by the systematic optimization of a laminated glass LSC design, demonstrated herein. In particular, we first show that it is possible to improve optical and electrical efficiencies of an LSC by fine-tuned optimization of the constituent fluorophore-containing interlayer resin. Further still, an increased understanding of commercially available solar cells allows us to establish a direct correlation between the device's optical and electrical efficiency. Next, optical characterization of LSCs of varying sizes allows us to elucidate the main loss mechanisms in our LSCs, as well as ways to mitigate them. Altogether these optimization steps create opportunities for high-performance multi-interlayer LSC devices with demonstrated electrical power conversion efficiency as high as 1.1% to 4.9% at visual light transmission of 74% to 5%. Furthermore, careful examination of different blue-color (red-band absorbing) dyes provides a path for color-tunability of LSC windows toward neutral regimes. Design iterations of multiple device form factors enabled a color-neutral prototype without significant performance losses by separating color-neutralizing and LSC layers into different panes of an insulated glass unit. This work demonstrates the importance of LSC design optimization in achieving high-performance solar window technology with commercially acceptable aesthetics.

Singlet Exciton Dynamics of Perylene Diimide- and Tetracene-Based Hetero/Homogeneous Substrates via an Ab Initio Kinetic Monte Carlo Model

Luminescent solar concentrators (LSCs) are devices that trap a portion of the solar spectrum and funnel it toward photon-harvesting devices. The modeling of LSCs at a quantum chemical level, however, remains a challenge due to the complexity of exciton and photon dynamic modeling. This study examines singlet exciton dynamics occurring within a typical LSC device. To do this, we use a rejection-free kinetic Monte Carlo method to predict diffusion lengths, diffusion coefficients, substrate anisotropy, and average exciton lifetimes of perylene diimide (PDI)- and tetracene-based substrates in the low-concentration scheme. Ab initio rate constants are computed using time-dependent density functional theory-based methods. PDI-type substrates are observed to display enhanced singlet exciton transport properties compared to tetracene. Simulations show that substrates with dipole-aligned chromophores are characterized by anisotropic exciton diffusion, with slightly improved transport properties. Finally, a PDI–tetracene substrate is simulated for both disordered and dipole-aligned chromophore configurations. In this multidopant substrate, transport is predominantly mediated by PDI due to the asymmetry in the transport rates between the two dyes considered. We conclude by discussing the properties of multidopant substrates and how they can impact the design of next-generation LSCs.

Soft luminescent solar concentrator film with organic dye and rubbery matrix

AbstractWe propose a soft luminescent solar concentrator (LSC) with superior light propagation. The rubbery poly(ethylene‐co‐vinyl acetate) (EVA) was adopted to replace the conventional brittle poly(methyl methacrylate) (PMMA). We analyzed the transmittance, photoluminescence efficiency, crystallinity, and surface properties of LSC to understand the optical and structural properties of the LSC. In addition, we modified the optical slab model to provide insights into the optical phenomenon in plate‐type LSC devices; we evaluated the solar absorption efficiency of the glass and emitting layers. We also evaluated the solar concentration performances of the LSC devices by measuring the photocurrent density generated using a monocrystalline silicon solar cell. We compared the transporting ability of emitted light into an edge by calculating the collection efficiency based on the concentration factor and optical efficiencies (absorption and photoluminescence). The concentration factor, optical efficiency, and collection efficiency of the EVA‐LSC with 4000 ppm of Lumogen F Red 305 were 0.31, 3.1, and 40%, respectively. The overall optical properties of the EVA‐LSC were comparable to those of the PMMA‐LSC. Moreover, the light decay property of EVA‐LSC was superior by 1.2 times than PMMA‐LSC. Therefore, we suggest EVA can replace PMMA and be used for flexible and large‐area LSC applications.

Highly emissive fluorescent silica-based core/shell nanoparticles for efficient and stable luminescent solar concentrators

Luminescent solar concentrators (LSCs) represent a viable spectral conversion technology to maximize sunlight harvesting while promising to reduce the current gap for integration of solar cells into the built environment. In this work, novel highly emissive and photostable core-shell nanostructured luminescent species were synthesized and used in LSC devices. Such systems were obtained by entrapping Lumogen F Red 305 in silica-based shells by means of the sol-gel process using a combination of hydrophilic (tetraethyl orthosilicate) and hydrophobic (phenyltriethoxysilane) silica precursors. By tuning their relative proportions during the synthetic process, fine control over the characteristic dimensions and morphology of the obtained dye-doped core-shell nanoparticles could be achieved, leading to a maximum concentration of non-covalently entrapped fluorescent dye of ~ 1 wt%. Optical characterization showed that the newly synthetized nanoparticles displayed markedly improved photoluminescence quantum yield in solid state (~ 95%) with respect to the non-encapsulated dye (~ 2%), as a result of an effective suppression of dye aggregation and fluorescence quenching phenomena. In addition, their excellent photostability under harsh UV light exposure was demonstrated, resulting from the protective action of the encapsulating hybrid silica-based shell, which can effectively limit photobleaching of the luminescent core. Their incorporation in thin-film LSCs led to a maximum internal photon efficiency as high as ~ 29%, thus providing evidence of their suitability as highly performing luminescent species with superior optical response and excellent photostability. Also, a maximum external photon efficiency as high as 2.12% was achieved. This work provides the first demonstration of silica-based encapsulation of Lumogen F Red 305 and of the application of silica-based core-shell nanoparticles in LSCs, thus paving the path to the development of a new class of highly efficient and stable nanostructured luminophores for the photovoltaic field. The first demonstration of silica-based encapsulation of Lumogen F Red 305 and of the application of silica-based core-shell luminescent species in LSCs is given, thus opening the path to the development of highly efficient and stable nanostructured luminophores for the photovoltaic field. • Novel nanostructured luminescent species are synthetized. • The nanostructured luminophores are based on hybrid core-shell silica nanoparticles. • Such nanoparticles exhibit enhanced luminescence quantum yield and photostability. • Their use as luminophores in luminescent solar concentrators (LSCs) is demonstrated. • The obtained LSCs exhibit high efficiency and prolonged stability.

Should Anisotropic Emission or Reabsorption of Nanoparticle Luminophores Be Optimized for Increasing Luminescent Solar Concentrator Efficiency?

For the optimization of solar‐to‐electricity conversion efficiency of luminescent solar concentrators (LSCs), luminophores are treated as isotropic emitters. As rod‐shaped nanocrystals are being developed, their anisotropic emission properties may be beneficial for LSC efficiency, as it is expected that escape cone losses can be reduced by proper alignment of nanorods (NRs). Herein, theoretical considerations and Monte Carlo ray‐tracing simulations are used to examine the effect of anisotropic emission of luminophores on LSC performance, using nonspherical nanoparticles. Three different nanoparticles are examined with different Stokes shift and with two different quantum yield (QY) values (QY = 1 and QY = 0.7). In the case of a rod‐shaped emitter with emission intensity distribution aligned perpendicular to the lightguide plane, escape cone losses can potentially be reduced to ≈9%, compared to 25.5% for isotropic emission. For more realistic anisotropic emitters, escape cone losses reduce to ≈19%. Nonetheless, it is found that the useful emission of isotropic quantum dots with low reabsorption is much larger than that of aligning anisotropic emitting NRs with high reabsorption. Hence, focus on reducing reabsorption loss yields larger improvements in LSC device efficiency than focus on aligned NRs.

A luminescent solar concentrator ray tracing simulator with a graphical user interface: features and applications

A Monte-Carlo ray tracing simulator with a graphical user interface (MCRTS-GUI) has been developed to provide a quantitative description, performance evaluation and photon loss analysis of luminescent solar concentrators (LSCs). The algorithm is applied to several practical LSC device structures including multiple dyes in the same waveguiding layer, and structures where a dye layer is sandwiched between clear substrates. The effect of the host matrix absorption and the influence of the neighboring layers are investigated. Validations demonstrate that the MCRTS-GUI developed provides a reliable and accurate description of LSC performance. Code for the mixed-dye single layer configuration is converted into a ray-tracing package with a user-friendly interface and is made available as open source software.