The luminescent solar concentrator (LSC), originally introduced almost four decades ago as a potential alternative/complement to silicon solar cells, has since evolved to a versatile photovoltaic ...(PV) solution with realistic potential for seamless integration into the urban architectural landscape. Yet, a popular perception of the device still persists: the LSC is mostly seen as just a low‐efficiency solar panel. This review challenges this outdated notion and argues that the LSC is, to the contrary, a powerful and highly adaptive photonic platform with many more capabilities and potential than only generating electricity from sunlight. The field has seen a rapidly expanding application portfolio over the last few years, with LSCs now considered in various sensing applications, “smart” windows, chemical reactors, horticulture, and even in optical communication and real‐time responsive systems. The main goal of this work is to shed light onto this alternative application space and highlight the LSC's unique spectral manipulation, light distribution, and light concentration properties, and as a result, to encourage the participation from a broader range of disciplines into LSC research with the ultimate aim of stimulating the development of novel, LSC inspired technologies.
Luminescent solar concentrators are typically seen as flat, planar devices for concentrating sunlight; however, the devices have recently been employed in a much broader range of configurations and applications. Here the versatile and innovative methods in which these devices have been employed are explored, reaching industries including agriculture, sensing, imaging, and communications.
Luminescent solar concentrators (LSCs) show great potential for both broadening the spectral response of photovoltaic devices and facilitating their deployment in urban environments. However, the ...recent success of LSCs has brought to light severe deficiencies in reporting protocols: direct comparison between lab-scale LSCs is not possible due to inconsistencies in the experimental measurements and reporting of device performance. Here, we make the case for treatment of LSCs as photonic devices rather than photovoltaic cells and identify best practice guidelines for the measurement and reporting of LSC performance.
Recommendation of standardised experiments for adoption by all researchers on luminescent solar concentrators to unify reporting and legitimise the field.
Windows are vital elements in the built environment that have a large impact on the energy consumption in indoor spaces, affecting heating and cooling and artificial lighting requirements. Moreover, ...they play an important role in sustaining human health and well‐being. In this review, we discuss the next generation of smart windows based on organic materials which can change their properties by reflecting or transmitting excess solar energy (infrared radiation) in such a way that comfortable indoor temperatures can be maintained throughout the year. Moreover, we place emphasis on windows that maintain transparency in the visible region so that additional energy is not required to retain natural illumination. We discuss a number of ways to fabricate windows which remain as permanent infrared control elements throughout the year as well as windows which can alter transmission properties in presence of external stimuli like electric fields, temperature and incident light intensity. We also show the potential impact of these windows on energy saving in different climate conditions.
In this review, smart windows are discussed which reflect excess of solar energy (infrared radiations) in summer and allow entrance into the building during winter, without interfering with visible light, to save significant amounts of energy in heating, cooling and lighting.
Nature provides much inspiration for the design of materials capable of motion upon exposure to external stimuli, and many examples of such active systems have been created in the laboratory. ...However, to achieve continuous motion driven by an unchanging, constant stimulus has proven extremely challenging. Here we describe a liquid crystalline polymer film doped with a visible light responsive fluorinated azobenzene capable of continuous chaotic oscillatory motion when exposed to ambient sunlight in air. The presence of simultaneous illumination by blue and green light is necessary for the oscillating behaviour to occur, suggesting that the dynamics of continuous forward and backward switching are causing the observed effect. Our work constitutes an important step towards the realization of autonomous, persistently self-propelling machines and self-cleaning surfaces powered by sunlight.
Research on the luminescent solar concentrator (LSC) over the past thirty‐odd years is reviewed. The LSC is a simple device at its heart, employing a polymeric or glass waveguide and luminescent ...molecules to generate electricity from sunlight when attached to a photovoltaic cell. The LSC has the potential to find extended use in an area traditionally difficult for effective use of regular photovoltaic panels: the built environment. The LSC is a device very flexible in its design, with a variety of possible shapes and colors. The primary challenge faced by the devices is increasing their photon‐to‐electron conversion efficiencies. A number of laboratories are working to improve the efficiency and lifetime of the LSC device, with the ultimate goal of commercializing the devices within a few years. The topics covered here relate to the efforts for reducing losses in these devices. These include studies of novel luminophores, including organic fluorescent dyes, inorganic phosphors, and quantum dots. Ways to limit the surface and internal losses are also discussed, including using organic and inorganic‐based selective mirrors which allow sunlight in but reflect luminophore‐emitted light, plasmonic structures to enhance emissions, novel photovoltaics, alignment of the luminophores to manipulate the path of the emitted light, and patterning of the dye layer to improve emission efficiency. Finally, some possible ‘glimpses of the future’ are offered, with additional research paths that could result in a device that makes solar energy a ubiquitous part of the urban setting, finding use as sound barriers, bus‐stop roofs, awnings, windows, paving, or siding tiles.
Research on the luminescent solar concentrator (LSC) is reviewed. The LSC is a simple, easily adaptable device for urban integration, employing a polymeric or glass waveguide and luminescent molecules which could generate electricity from sunlight in combination with photovoltaic cells.
Recent years have seen major advances in the developments of both additive manufacturing concepts and responsive materials. When combined as 4D printing, the process can lead to functional materials ...and devices for use in health, energy generation, sensing, and soft robots. Among responsive materials, liquid crystals, which can deliver programmed, reversible, rapid responses in both air and underwater, are a prime contender for additive manufacturing, given their ease of use and adaptability to many different applications. In this paper, selected works are compared and analyzed to come to a didactical overview of the liquid crystal‐additive manufacturing junction. Reading from front to back gives the reader a comprehensive understanding of the options and challenges in the field, while researchers already experienced in either liquid crystals or additive manufacturing are encouraged to scan through the text to see how they can incorporate additive manufacturing or liquid crystals into their own work. The educational text is closed with proposals for future research in this crossover field.
Liquid crystals are the basis for many “smart” materials used in, for instance, soft robotics and polymer optics. Recently, their potential and appeal for different additive manufacturing techniques has been demonstrated. Insight into the usage of liquid crystals in 3D printing for fabrication at both micro‐ and centimeterscale is provided for those wanting to join this exciting, developing field.
A new type of “smart” window is proposed that makes use of fluorescent dye guests in a liquid‐crystal host sandwiched between glass panels. The dye absorbs a variable amount of light depending on its ...orientation, and re‐emits this light, of which a significant fraction is trapped by total internal reflection at the glass–air interface, and becomes concentrated along the edges. Such a device could both generate electricity via an attached photovoltaic as well as allow user control of the amount of transmitted light. By applying a voltage across the cell, absorption could be varied 31%, while the usable light output only varied 11% due to the increased efficiency of light collection at homeotropic dye orientation.
A new “smart” window design based on a fluorescent guest/liquid‐crystal host is introduced, which may be externally modulated to vary light transmission while simultaneously generating electricity via an attached photovoltaic cell. Shown in the photograph are two filled cells in the “off” (left) and “on” states (right).
The use of solar light to promote chemical reactions holds significant potential with regard to sustainable energy solutions. While the number of visible light‐induced transformations has increased ...significantly, the use of abundant solar light has been extremely limited. We report a leaf‐inspired photomicroreactor that constitutes a merger between luminescent solar concentrators (LSCs) and flow photochemistry to enable green and efficient reactions powered by solar irradiation. This device based on fluorescent dye‐doped polydimethylsiloxane collects sunlight, focuses the energy to a narrow wavelength region, and then transports that energy to embedded microchannels where the flowing reactants are converted.
An artificial tree leaf: A device integrating the concept of the luminescent solar concentrator with a photomicroreactor makes it possible to harvest solar light efficiently for use in photochemical reactions. This tree‐leaf‐inspired photomicroreactor collects sunlight, focuses the energy to a narrow wavelength region, and then transports the energy to embedded microchannels where the flowing reactants are converted.
The iridescence of structural color and its polarization characteristics originate from the nanoscale organization of materials. A major challenge in materials science is generating the bright, ...lustrous hues seen in nature through nanoscale engineering, while simultaneously controlling interaction of the material with different light polarizations. In this work, a suitable chiral nematic liquid crystal elastomer ink is synthesized for direct ink writing, which self‐assembles into a chiral photonic structure. Tuning the writing direction and speed leads to the programmed formation of a slanted photonic axis, which exhibits atypical iridescence and polarization selectivity. After crosslinking, a freely programmable, chiroptical photonic polymer material is obtained. The strongly perspective‐dependent appearance of the material can function as specialized anticounterfeit markers, as optical elements in decorative iridescent coatings, or, as demonstrated here, in optically based signaling features.
Inspired by natural examples of patterned iridescence, an ink based on a chiral nematic liquid crystal that can be processed with a direct ink writer 3D printer is shown. Tuning the writing direction and speed leads to the programmed formation of a slanted photonic axis that exhibits atypical iridescence and polarization selectivity.
Arbitrary shape (re)programming is appealing for fabricating untethered shape‐morphing photo‐actuators with intricate configurations and features. We present re‐programmable light‐responsive ...thermoplastic actuators with arbitrary initial shapes through spray‐coating of polyethylene terephthalate (PET) with an azobenzene‐doped light‐responsive liquid crystal network (LCN). The initial geometry of the actuator is controlled by thermally shaping and fixing the thermoplastic PET, allowing arbitrary shapes, including origami‐like folds and left‐ and right‐handed helicity within a single sample. The thermally fixed geometries can be reversibly actuated through light exposure, with fast, reversible area‐specific actuation such as winding, unwinding and unfolding. By shape re‐programming, the same sample can be re‐designed and light‐actuated again. The strategy presented here demonstrates easy fabrication of mechanically robust, recyclable, photo‐responsive actuators with highly tuneable geometries and actuation modes.
Thermoplastic polyethylene terephthalate (PET) were spray‐coated with an azobenzene‐doped liquid‐crystal network (LCN). Arbitrary shapes are programmed by thermal shaping and fixing of PET, enabling untethered, area‐specific light response with origami‐like folds. The thermoplastic actuator demonstrates multi‐modal shape morphing in a single sample and can be re‐designed and light‐actuated repeatedly.
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