Perylene dye photodegradation due to ketones and singlet oxygen

The photodegradation rate of a perylene dye (Lumogen F Yellow 083) in methyl isobutyrate was found to increase with ketone concentration for two different ketones. Of the ketones employed, methyl pyruvate, an impurity in methyl methacrylate, was found to be particularly deleterious to dye stability. In agreement with other published studies, the addition of the anti-oxidant DABCO (1,4-diazabicyclo-[2.2.2] octane) to the dye matrix was found to increase dye stability; however when ketones were present, DABCO lead to increased photodegradation. These results highlight the importance of removing ketone impurities from dye matrices during production of Luminescent Solar Concentrators (LSCs). © 2009 Elsevier Ltd. All rights reserved

Lifetime and efficiency improvement of organic luminescent solar concentrators for photovoltaic applications

In order to achieve the goal of zero net-energy consumption in residential and commercial buildings, substantial research has been devoted to developing methods for energy harvesting from window glass that is capable of passing visible light through the windows of buildings while converting the unwanted invisible solar radiation into electricity. Research has focussed on two particular aspects, namely (i) the integration of thin-film technology for solar radiation transmission control and (ii) light guiding structures for solar radiation routing towards the edges of the glass window. Recently, photovoltaic (PV) solar cells have been investigated and promoted as products for converting solar energy into electricity. Due to the increased demand for renewable energy sources, the manufacture of PV panels’ arrays has advanced considerably. However, they cannot compete with fossil fuel or nuclear energy, due to the high cost of inorganic solar cells and their low power conversion efficiency (PCE). To lower the cost per installed capacity ($/Watt) and to use the complete solar spectrum, new PV technologies have been developed, such as solar concentrators. Among the many kinds of concentrators, luminescent solar concentrators (LSCs) have significant industry application potential. Materials used in LSCs are inexpensive, the solar cell size is reduced and no tracking of the sun is required. In an LSC, the incident sunlight is absorbed by luminescent species, such as fluorescent dyes, quantum dots or rare-earth ion embedded in the active layer (organic or inorganic), which re-emits light in random directions usually at longer wavelengths. In an ideal LSC, all the re-emitted light can be routed towards the edges, where the attached small-area solar cells harvest the light and convert it into electricity. In this thesis, several contributions are made toward the development of organic LSCs. The first contribution is related to the design and development of multilayer thin film structures containing dielectric and metal layers, using physical vapour deposition, for the control of thermal and solar radiation propagated through glass windows. Measured transmittance spectra for the developed thin-film structures are in excellent agreement with simulation results. For the second contribution, a cost-effective, long-life-time organic LSC device with UV epoxy as a waveguide layer doped by two organic materials is developed. A PCE as high as 5.3% and a device lifetime exceeding 1.0×105 hrs are experimentally achieved. The third contribution of the thesis is the development of a general method for encapsulating organic LSCs, based on employing three optically transparent layers, (i) an encapsulating epoxy layer and (ii) two insulating SiO2 layers that prevent the dye dissolving into the epoxy layer. The encapsulated organic LSCs demonstrate an ultra-long lifetime of ~ 3.0×104 hrs and 60% transparency when operated in an ambient environment, of around 5 times longer than that of organic LSCs without encapsulation. Finally, the last contribution of the thesis is the development of a new LSC architecture that mitigates the reabsorption loss typically encountered in LSCs. Experimental results demonstrate significant reduction in photon reabsorption, leading to a 21% increase in PCE, in comparison with conventional LSCs

On the Ability of Förster Resonance Energy Transfer to Enhance Luminescent Solar Concentrator Efficiency

Developing means to reduce the cost of solar energy is vital to curb our carbon footprint over the upcoming decades. A luminescent solar concentrator (LSC) is a potential solution as it provides light concentration without any tracking device and can be readily integrated into the built environment. In this study we report on an advanced LSC design that employs quantum dots as absorption fluorophores and organic dye molecules as emission fluorophores. By linking the two types of fluorophores to each other, energy is transferred efficiently via Förster resonance energy transfer (FRET) from the quantum dot to the dye molecule. This novel method makes use of the quantum dot's spectrally wide absorption profile and the higher quantum yield of the dye. We show that our design can overcome the losses normally incurred due to a low quantum yield emitter by transferring the absorbed energy to a linked fluorophore with a higher quantum yield. Our experimental measurements show FRET can enhance the optical efficiency of a LSC by at least 24.7%. The maximum theoretical efficiency has been investigated by ray-tracing and has been found to be 75.1%; this represents a relative improvement of even 215.5% compared to a LSC doped with quantum dots only (23.8%), showing the great potential of our concept. Our design will initiate interest in fluorophores which have not been considered for LSC applications thus far because of their low quantum yield or small Stokes shift

“N-alkyl diketopyrrolopyrrole-based fluorophores for luminescent solar concentrators: effect of the alkyl chain on dye efficiency”

We report on the preparation of luminescent solar concentrators (LSCs) made of poly(methyl methacrylate) (PMMA) thin films doped with six new diketopyrrolopyrrole (DPP) fluorophores obtained in good yields by using simple N-alkylation and direct C-H arylation synthetic strategies. Spectroscopic investigations in solution and in PMMA thin films combined with photocurrent measurements revealed that the branched alkyl chains were efficient in preventing DPP segregation from the PMMA matrix thanks to their higher steric hindrance. The aromatic substituent was found to expand DPP conjugation but favoured DPP adverse aggregation, thus affecting fluorescence emission and photocurrents of PMMA films. The worthwhile combination of the appropriate alkyl chain and aromatic moieties assured to achieve optical efficiency of 6.8% that was comparable to that of PMMA LSCs of the state-of-the art (7.2%)

Fabrication of a luminescent solar concentrator that minimizes self-absorption losses using inter-chromophore energy transfer

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2007.Includes bibliographical references (p. 57-59).The projected need for carbon-free power during this century is immense. Solar power offers the largest resource base to supply this need, but in light of recent silicon shortages, it is an open question whether silicon photovoltaics can keep pace with demand. The development of economical concentrators could relieve this resource pressure. The luminescent solar concentrator (LSC) is an architecture that collects and concentrates light using the luminescent properties of chromophores embedded in a waveguide. This method of concentration alleviates the need for expensive tracking equipment necessary for optical concentration. Combined with the low cost and flexible fabrication of organic materials, this technology is inherently scalable. A major limitation to LSC efficiency is self-absorption between different chromophores within the waveguide. Finding inspiration from the architecture of phycobilisome antenna complexes, a system of chromophores is developed that minimizes self-absorption through Firster energy transfer. Precise control of intermolecular spacing is achieved through thermal evaporation of small molecule organics. A LSC with a geometric gain of 25 is fabricated that employs this optimized system. External quantum efficiencies of 32% are achieved across nearly half the visible spectrum, with a total power conversion efficiency of 1.6%. Additionally, modeling and theory are presented to highlight places for device improvement. It is shown that a simple path integral successfully captures the dynamics of the LSC.by Michael James Currie.S.M

Concentradores solares luminescentes de elevado desempenho para conversão fotovoltaica baseada em guias de onda flexíveis

The mismatch between the AM1.5G spectrum and photovoltaic cell absorption is one of the critical factors limiting their performance. To overcome it, several approaches have been proposed. Among them, emphasis is given to luminescent down-shifting layers, additive devices that are able to enhance performance under typical operation conditions, and to luminescent solar concentrators, a complementary technology to PV cells for use in urban environments. Luminescent down-shifting layers are coatings that are directly deposited on the surface of photovoltaic cells, and absorb the incident radiation that is not absorbed by photovoltaic cells, subsequently re-emitting it at a specific wavelength and refracting/reflecting it towards the photovoltaic cell. Luminescent solar concentrators are devices comprising a transparent matrix incorporating optically active centres that absorb the incident radiation, which is then re-emitted at a specific wavelength and transferred by total internal reflection to photovoltaic cells located at the edges of the matrix. This configuration enables photovoltaic devices to be embedded in building facades or windows, allowing them to be transformed into energy harvesting units, contributing for the development of zero-energy buildings. This thesis aimed to produce and characterize transparent organic- inorganic hybrids with controlled thickness and refractive index using poly(methyl methacrylate), di- and triureasils incorporating different lanthanide ions, namely Tb3+, Eu3+, Y b3+ and Nd3+, and the fol- lowing organic dyes: Rhodamine 6G and Rhodamine 800, silicon 2,3- naphthalocyaninebis(trihexylsilyloxide), chlorophyll and R- phycoerythrin molecules with emission tuned from the visible to NIR spectral regions. LSCs with planar and cylindrical geometry are studied. The use of the cylindrical geometry allows the effect of concentration to be higher when compared with the planar geometry, since the ratio between the exposed area and the area of the edges is increased. The cylindrical geometry concentrators are produced from plastic optical fibres with hollow cores, where the optically active layer was injected. The exposed area was further optimised through the production of bundles of LSCs, in which optical fibres with different cladding geometries were placed side by side. Finally, the attractive properties of natural-based dye molecules for the production of luminescent solar concentrators, which have been poorly explored, are also studied through the incorporation of chlorophyll and R- phycoerythrin as optically active centres. Key experimental results were also validated using Monte-Carlo ray-tracing simulations.O desfasamento entre o espetro AM1.5G e o espetro de absorção das células fotovoltaicas é um fator crítico que limita o desempenho das mesmas. De forma a ultrapassar isto, diversas aproximações têm sido propostas. Entre elas, têm sido enfatizadas as camadas luminescentes por desvio descendente de energia, dispositivos capazes de melhorar o desempenho em condições de operação específicas, e os concentradores solares luminescentes, considerados uma tecnologia complementar a das células fotovoltaicas para utilização em ambientes urbanos. As camadas luminescentes por desvio descendente de energia são revestimentos diretamente depositados no topo de células fotovoltaicas capazes de absorver a radiação incidente complementar à que as células fotovoltaicas absorvem e subsequentemente reemitem-na com um comprimento de onda específico que é refratado/refletido até à célula fotovoltaica. Os concentradores solares são dispositivos compostos por uma matriz transparente incorporando centros óticos ativos que absorbem a radiação incidente, que é posteriormente reemitida com um comprimento de onda específico e transportada por reflexão interna total até à célula fotovoltaica localizada nas extremidades da matriz. Esta configuração permite a produção de dispositivos fotovoltaicos embebidos em fachadas de edifícios e janelas, permitindo que estes sejam transformados em unidades de produção de energia, contribuindo para o desenvolvimento de edifícios de energia zero. O principal objetivo deste trabalho consiste no fabrico e caracterização de híbridos orgânicos-inorgânicos com espessura e índice de refração controlados utilizando polimetil-metacrilato, di- e tri-ureasil incorporando diferentes iões lantanídeos, nomeadamente Tb3+, Eu3+, Yb3+ and Nd3+, e corantes orgânicos como Rodamina 6G, Rodamina 800, Silício 2,3-naftalocianina bis(trietil siloxano), clorofila e R-ficoeritrina cuja emissão varia entre o visível e o infravermelho próximo. Concentradores solares luminescentes com geometria planares e cilíndrica foram estudados. A geometria cilíndrica permite que o efeito de concentração seja superior, quando comparado com a geometria planar, uma vez que a razão entre a área exposta e a área das extremidades aumenta. A geometria cilíndrica é explorada, através da produção de concentradores solares luminescentes em fibra ótica de plástico onde a camada ótica ativa se encontra no interior da fibra, como um preenchimento do núcleo oco. A possibilidade de aumentar a área exposta foi, também, abordada através do fabrico de uma matriz de concentradores solares luminescentes colocados lado a lado com diferentes geometrias da bainha. Para além disso, as propriedades óticas dos corantes orgânicos naturais, que têm sido pouco exploradas na literatura, foram alvo de estudo através da incorporação de moléculas de clorofila e de R-ficoeritrina como centros óticos em concentradores solares luminescentes. Os resultados experimentais mais relevantes foram validados através de simulações baseadas no método de Monte-Carlo.Programa Doutoral em Físic

Status report on emerging photovoltaics

\ua9 2023 Society of Photo-Optical Instrumentation Engineers (SPIE).This report provides a snapshot of emerging photovoltaic (PV) technologies. It consists of concise contributions from experts in a wide range of fields including silicon, thin film, III-V, perovskite, organic, and dye-sensitized PVs. Strategies for exceeding the detailed balance limit and for light managing are presented, followed by a section detailing key applications and commercialization pathways. A section on sustainability then discusses the need for minimization of the environmental footprint in PV manufacturing and recycling. The report concludes with a perspective based on broad survey questions presented to the contributing authors regarding the needs and future evolution of PV

Doped polymer optical fibers for high performance fluorescent fiber applications.

205 p.La sociedad actual ha experimentado los mayores y más destacados avances tecnológicos desde la Revolución Industrial a finales del siglo XIX. El desarrollo en ámbitos como el transporte, las comunicaciones, la medicina o la producción de energía, entre otros, se ha convertido en el pilar principal del progreso global actual. En este contexto, esta tesis engloba el uso de fibras ópticas de plástico dopadas en dos áreas en pleno desarrollo y muy demandadas por la sociedad moderna: comunicaciones ópticas (láseres y amplificadores de fibra) y producción de energía sostenible (concentración de luz solar mediante fibras dopadas)

Monte-Carlo Ray-Trace Modelling of Quantum Dot Solar Concentrators

Due to the finite resources of fossil fuel and nuclear reserves, renewable energy technologies much provide an increasing proportion of future energy needs, if the world’s population are to expect a secure and sustainable developed society. Quantum dot solar concentrators (QDSCs) can potentially reduce the cost of photovoltaic (PV) electrical power generation and thereby further the growth in installed PV capacity. QDSCs can concentrate both the direct and diffuse components of solar radiation which makes them particularly suitable for climates where the diffuse component is predominant. A QDSC model has been developed based on Monte-Carlo ray-trace techniques. The model allows the multiple competing, interdependent QDSC loss mechanisms to be quantified for any given set of device parameters. The model provides an important tool for optimizing QDSC design in terms of varying geometry, PV cell configuration, matrix material, and quantum dot types. Combining the ray-trace model with solar radiation models, diurnal and seasonal variations in QDSC performance can be analysed, the devices further optimised for outdoor conditions. Model predictions show that variable QDSCs are realizable provided efficient near intra-red emitting quantum dots can be exploited

Host Matrix Materials for Luminescent Solar Concentrators: Recent Achievements and Forthcoming Challenges

Luminescent solar concentrators (LSCs) have attracted increasing attention in the past few years as appealing solar energy technology for the seamless integration of photovoltaic (PV) systems into the built environment. Traditionally, research in this field has focused on two main aspects: the optimization of the device assembly, in the quest for more efficient architectures to maximize collection, transport, and conversion of photons into usable electrical energy; the development of novel, highly emissive luminescent species, to ensure broad light collection and efficient photon emission. Only recently, the attention has also been directed toward the selection and development of suitable host matrix/waveguide materials with appropriate optical properties, sufficient chemical compatibility with the guest luminescent species, good processability for easy device fabrication and prolonged durability in outdoor operation. In addition to consolidated polymeric systems based on polyacrylates or polycarbonates, in recent years different examples of alternative host matrix systems have been proposed, characterized by peculiar chemical, physical and optical characteristics specifically designed to meet the stringent requirements of the LSC technology. This mini-review will focus on recent developments in the design of new host matrix materials for LSC applications. An overview of the most recent examples of novel LSC host matrices will be provided here, mainly focusing on new polymers, polymer-based organic-inorganic hybrids and multifunctional organic systems. Finally, opportunities and challenges in the field will be considered in view of the effective exploitation of the LSC technology in real application scenarios