Solar Energy Conversion with Fluorescent Collectors
TL;DR: In this article, a new principle for solar energy conversion is proposed and evaluated theoretically, and the optical path length in a triangular collector is computed, which offers the advantage of separating the various fractions of light and converting them with solar cells with different bandgaps.
Abstract: A new principle for solar energy conversion is proposed and evaluated theoretically. Collection and concentration of direct and diffuse radiation is possible by the use of a stack of transparent sheets of material doped with fluorescent dyes. High efficiency of light collection can be achieved by light guiding and special design of collectors. The optical path length in a triangular collector is computed. In combination with solar cells this type of collector offers the advantage of separating the various fractions of light and converting them with solar cells with different bandgaps. Theoretical conversion efficiency under optimum conditions is 32% for a system with four semiconductors. Thermal energy conversion offers several advantages over conventional collectors: High temperature and efficiency even under weak illumination, separation of heat transport and radiation collection, low thermal mass. Thermal efficiency is computed to be between 42% and 60%. Very attractive appear hybrid systems for generation of thermal and electric energy. An estimate of the economics of electricity generation shows that due to the concentration costs can be much lower than possible today. With the use of only silicon cells the breakeven point of $0.5/W is almost reached. Practical difficulties to be solved are: Synthesis of dyes with stringent requirements, identification of plastic materials with high transparency and development of solar cells with higher bandgaps.
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TL;DR: This paper is a review of recent progress made in organic thin films grown in ultrahigh vacuum or using other vapor-phase deposition methods and describes the most important work which has been published in this field since the emergence of OMBD in the mid-1980s.
Abstract: During the past decade, enormous progress has been made in growing ultrathin organic films and multilayer structures with a wide range of exciting optoelectronic properties. This progress has been made possible by several important advances in our understanding of organic films and their modes of growth. Perhaps the single most important advance has been the use of ultrahigh vacuum (UHV) as a means to achieve, for the first time, monolayer control over the growth of organic thin films with extremely high chemical purity and structural precision.1-3 Such monolayer control has been possible for many years using well-known techniques such as Langmuir-Blodgett film deposition,4 and more recently, self-assembled monolayers from solution have also been achieved.5 However, ultrahighvacuum growth, sometimes referred to as organic molecular beam deposition (OMBD) or organic molecular beam epitaxy (OMBE), has the advantage of providing both layer thickness control and an atomically clean environment and substrate. When combined with the ability to perform in situ highresolution structural diagnostics of the films as they are being deposited, techniques such as OMBD have provided an entirely new prospect for understanding many of the fundamental structural and optoelectronic properties of ultrathin organic film systems. Since such systems are both of intrinsic as well as practical interest, substantial effort worldwide has been invested in attempting to grow and investigate the properties of such thin-film systems. This paper is a review of recent progress made in organic thin films grown in ultrahigh vacuum or using other vapor-phase deposition methods. We will describe the most important work which has been published in this field since the emergence of OMBD in the mid-1980s. Both the nature of thin-film growth and structural ordering will be discussed, as well as some of the more interesting consequences to the physical properties of such organic thin-film systems will be considered both from a theoretical as well as an experimental viewpoint. Indeed, it will 1793 Chem. Rev. 1997, 97, 1793−1896
1,809 citations
TL;DR: The luminescent solar concentrator (LSC) is a simple device at its heart, employing a polymeric or glass waveguide and luminecent molecules to generate electricity from sunlight when attached to a photovoltaic cell as mentioned in this paper.
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.
779 citations
TL;DR: In this paper, the application of rare-earth-doped inorganic materials for achieving external quantum efficiencies greater than unity and enhancing the conversion efficiency of silicon solar cells was examined, and the opportunities for the DC of high-energy solar photons to multiple photons with energy greater than the silicon bandgap were discussed.
755 citations
Cites background from "Solar Energy Conversion with Fluore..."
...The application of down-shifting layers in PV include luminescent solar concentrators [2-4] and measures to overcome limitations in the front surface of some solar cell designs [5]....
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TL;DR: Recent advances in nanocrystal research related to applications of QD materials in lasing, light-emitting diodes (LEDs), and solar energy conversion are examined.
Abstract: The field of nanocrystal quantum dots (QDs) is already more than 30 years old, and yet continuing interest in these structures is driven by both the fascinating physics emerging from strong quantum confinement of electronic excitations, as well as a large number of prospective applications that could benefit from the tunable properties and amenability toward solution-based processing of these materials. The focus of this review is on recent advances in nanocrystal research related to applications of QD materials in lasing, light-emitting diodes (LEDs), and solar energy conversion. A specific underlying theme is innovative concepts for tuning the properties of QDs beyond what is possible via traditional size manipulation, particularly through heterostructuring. Examples of such advanced control of nanocrystal functionalities include the following: interface engineering for suppressing Auger recombination in the context of QD LEDs and lasers; Stokes-shift engineering for applications in large-area luminesce...
703 citations
TL;DR: This review captures the synthesis, assembly, properties, and applications of copper chalcogenide NCs, which have achieved significant research interest in the last decade due to their compositional and structural versatility.
Abstract: This review captures the synthesis, assembly, properties, and applications of copper chalcogenide NCs, which have achieved significant research interest in the last decade due to their compositional and structural versatility. The outstanding functional properties of these materials stems from the relationship between their band structure and defect concentration, including charge carrier concentration and electronic conductivity character, which consequently affects their optoelectronic, optical, and plasmonic properties. This, combined with several metastable crystal phases and stoichiometries and the low energy of formation of defects, makes the reproducible synthesis of these materials, with tunable parameters, remarkable. Further to this, the review captures the progress of the hierarchical assembly of these NCs, which bridges the link between their discrete and collective properties. Their ubiquitous application set has cross-cut energy conversion (photovoltaics, photocatalysis, thermoelectrics), en...
636 citations
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700 citations
01 Jul 1960
TL;DR: In this paper, seven factors limiting the performance of photovoltaic solar energy converters are listed and explained, which can be classified into basic and technology-decided limitations.
Abstract: Seven factors limiting the performance of photovoltaic solar energy converters are listed and explained. They can be classified into basic and technology determined limitations. Possibilities for improvement on technology determined limitations are investigated for the silicon solar cell. Such possibilities are: heavier p-layer doping; change of geometry, possibly by application of grid structures; improvement of the material constants; and utilization of drift fields for improved collection. Discussed are materials other than silicon in regard to their potential for better performance than that obtainable from the silicon solar cell; and finally, new methods of approach, such as the multilayer and the multiple transition solar cell. Both of these methods yield theoretically large improvements, but realization depends on further advances in compound semiconductor technology and in knowledge about localized centers in the forbidden gap. Limit conversion efficiencies of 38.2 per cent for a 3-layer cell and of 51 per cent for a 3-transition cell, compared to 23.6 per cent for a single p-n junction, single transition cell, are obtained. Also discussed are the possible merits of the application of the graded energy gap to photovoltaic energy converters, and potential improvement in collection efficiency is found for certain cases.
383 citations
IBM1
TL;DR: In this paper, a homojunction solar cell consisting of pGa1−xAlxAs−pGaAs-n GaAs was used to achieve power conversion efficiency of over 16% (corrected for contact area) measured in sunlight for air mass 1 at sea level, while efficiencies of 19-20% for an air mass value of 2 or more.
Abstract: Heterojunction solar cells consisting of pGa1−xAlxAs–pGaAs–n GaAs are grown by liquid‐phase epitaxy and exhibit power conversion efficiencies of over 16% (corrected for contact area) measured in sunlight for air mass 1 at sea level, while efficiencies of 19–20% are obtained for an air mass value of 2 or more. The improved efficiencies compared to conventional homojunction (Si and GaAs) cells are attributed to the reduction of series resistance and the reduction of surface recombination losses resulting from the presence of the heavily doped Ga1−xAlxAs layer. Open‐circuit voltages of 0.98–1.0 V and short‐circuit currents of 18–21 mA/cm2 (corrected for contact area) are observed for a solar input intensity of 98.3 mW/cm2.
117 citations