Lindsay R. Wilson

Bio: Lindsay R. Wilson is an academic researcher from Heriot-Watt University. The author has contributed to research in topics: Luminescent solar concentrator & Quantum yield. The author has an hindex of 5, co-authored 6 publications receiving 579 citations.

Advanced Material Concepts for Luminescent Solar Concentrators

Abstract: Sunlight that is incident on the front surface of a luminescent solar concentrator (LSC) is absorbed and subsequently re-emitted by luminescent materials. The resulting luminescence is transported to the edge of the LSC sheet and concentrated onto photovoltaic devices. Despite its potential for generating low-cost solar power, LSC development faces numerous challenges, the majority of which are related to the luminescent materials used in their design. Earlier LSC research focused on organic dyes, and while several of the shortcomings with these materials have been solved over time, some major challenges remain. This paper outlines the loss mechanisms that limit conversion efficiency of the LSC and highlights the role that advanced materials can play. Losses include nonunity fluorescence quantum yield (FQY), reabsorption losses, incomplete utilization of the solar spectrum, and escape cone losses. Long-term photostability is also discussed as it is essential for commercial feasibility of any solar technology. Past and current techniques, designed to reduce these losses, are described and their experimental achievements are discussed.

Measurement method for photoluminescent quantum yields of fluorescent organic dyes in polymethyl methacrylate for luminescent solar concentrators

Abstract: A method for measuring the photoluminescent quantum yields (PLQY) of luminescent organic dyes is presented. The self-absorption probability calculated at different dye concentrations is used to determine the absolute quantum yield from the observed values. The results for a range of commercially available dyes show high quantum yields, even at high concentrations, and an absence of quenching. The PLQY of several dye mixtures are also presented. The results indicate an absence of any reduction of PLQY in a dye mixture as compared with the individual PLQY of the dyes.

Characterization and reduction of reabsorption losses in luminescent solar concentrators

Abstract: The effects of excitation wavelength on the optical properties (emission spectrum and quantum yield) of a luminescent solar concentrator (LSC) containing a fluorescent organic dye (Lumogen F Rot 305) are studied. Excitation at wavelengths on the long-wavelength edge of the absorption spectrum of the dye results in redshifted emission, but the quantum yield remains constant at 100%. The origin of this effect and its consequences are discussed. The extent of the long-wavelength tail of the absorption spectrum of the dye is determined and the importance in reabsorption losses is shown. The optical efficiencies and photon transport probabilities of LSCs containing either an organic dye or a rare-earth lanthanide complex are compared using ray-tracing simulations and experiment. The optical efficiency is shown to depend strongly on the Stokes shift of the fluorophore. The lanthanide complex, which has a very large Stokes shift, exhibits a higher optical efficiency than the dye (64% cf. 50%), despite its lower quantum yield (86% cf. 100%).

Enhancement of Power Output From a Large-Area Luminescent Solar Concentrator With 4.8× Concentration via Solar Cell Current Matching

Abstract: The irradiance concentrated along the edges of a planar luminescent solar concentrator (LSC) is not uniform across their length. This geometrical effect results in a deviation of up to 40% between the extreme ends and the middle of an edge for a large-area LSC. Consequently, the typically in-series interconnected solar cells attached to the edges of the LSC are not illuminated equally resulting to current mismatch. It is shown that by reducing the lengths of the more central solar cells so that current matching is achieved, more cells can be attached to each edge. This way, the voltage and power output of the string can be increased. In this work, a 60 cm × 60 cm × 0.3 cm LSC with 26 solar cells mounted to its edges was constructed and characterized. These dimensions result in geometrical concentration of 50×, while the LSC exhibited average irradiance concentration of 4.8×. An increase of 15% in power output and efficiency is demonstrated via the reduction of the length of central cells, current matching, and the consequent connection of one more cell to the string of an edge. A solar-to-electric power conversion efficiency of 1.55% is reported for the large-area LSC module.

Lanthanide luminescence for functional materials and bio-sciences

Abstract: Recent startling interest for lanthanide luminescence is stimulated by the continuously expanding need for luminescent materials meeting the stringent requirements of telecommunication, lighting, electroluminescent devices, (bio-)analytical sensors and bio-imaging set-ups. This critical review describes the latest developments in (i) the sensitization of near-infrared luminescence, (ii) “soft” luminescent materials (liquid crystals, ionic liquids, ionogels), (iii) electroluminescent materials for organic light emitting diodes, with emphasis on white light generation, and (iv) applications in luminescent bio-sensing and bio-imaging based on time-resolved detection and multiphoton excitation (500 references).

Enhancing solar cell efficiency: the search for luminescent materials as spectral converters

Abstract: Photovoltaic (PV) technologies for solar energy conversion represent promising routes to green and renewable energy generation. Despite relevant PV technologies being available for more than half a century, the production of solar energy remains costly, largely owing to low power conversion efficiencies of solar cells. The main difficulty in improving the efficiency of PV energy conversion lies in the spectral mismatch between the energy distribution of photons in the incident solar spectrum and the bandgap of a semiconductor material. In recent years, luminescent materials, which are capable of converting a broad spectrum of light into photons of a particular wavelength, have been synthesized and used to minimize the losses in the solar-cell-based energy conversion process. In this review, we will survey recent progress in the development of spectral converters, with a particular emphasis on lanthanide-based upconversion, quantum-cutting and down-shifting materials, for PV applications. In addition, we will also present technical challenges that arise in developing cost-effective high-performance solar cells based on these luminescent materials.

Thirty Years of Luminescent Solar Concentrator Research: Solar Energy for the Built Environment

Abstract: 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.

Improving efficiency and stability of perovskite solar cells with photocurable fluoropolymers.

Abstract: Organometal halide perovskite solar cells have demonstrated high conversion efficiency but poor long-term stability against ultraviolet irradiation and water. We show that rapid light-induced free-radical polymerization at ambient temperature produces multifunctional fluorinated photopolymer coatings that confer luminescent and easy-cleaning features on the front side of the devices, while concurrently forming a strongly hydrophobic barrier toward environmental moisture on the back contact side. The luminescent photopolymers re-emit ultraviolet light in the visible range, boosting perovskite solar cells efficiency to nearly 19% under standard illumination. Coated devices reproducibly retain their full functional performance during prolonged operation, even after a series of severe aging tests carried out for more than 6 months.