Buy Softcover. FAQ Policy. About this book Photovoltaics, the direct conversion of sunlight to electricity, is now the fastest growing technology for electricity generation. Show all. Table of contents 10 chapters Table of contents 10 chapters Introduction Pages Black-Bodies, White Suns Pages Energy, Entropy and Efficiency Pages Single Junction Cells Pages Tandem Cells Pages Photoinduced optical absorption studies demonstrate a different excitation spectrum for the composite as compared to the sep.
A photoinduced ESR signal exhibits signatures of both the conducting polymer cation and the C60 anion. Because the photoluminescence in the conducting polymer is quenched by interaction with C60, the data imply that charge transfer from the excited state occurs on a picosecond time scale. The charge-sepd. American Chemical Society.
A review. While the efficiencies of org. Here, we discuss several different exptl. These include techniques ranging from x-ray diffraction and spectroscopy to electron microscopy and scanning probe microscopy. These methods provide complementary information to guide future materials design and device optimization efforts. A review of device structure and performance of bulk heterojunction solar cells with highly ordered one-dimensional nanostructured components of semiconducting conjugated polymers, dyes, and metal oxides.
The morphol. Recent progress and improvement of self-assembling one-dimensional materials for a donor-acceptor active layer as well as an electron-transporting layer in org. Strategies of the fabrication procedures and origin of the photophys. One-dimensional nanostructured semiconducting materials that are vertically phase-sepd. Cited By. This article is cited by 22 publications. Chemistry of Materials , 24 17 , DOI: Nanoimprinted Polymer Solar Cell.
ACS Nano , 6 4 , Antonio Facchetti. Chemistry of Materials , 23 3 , Vini Gautam, Monojit Bag, and K. The Journal of Physical Chemistry Letters , 1 22 , Marks, Milko E.
Journal of the American Chemical Society , 36 , New-generation integrated devices based on dye-sensitized and perovskite solar cells. Enhancement of photovoltaic performance by two-step dissolution processed photoactive blend in polymer solar cells.
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Journal of Energy Chemistry , 24 5 , The most promising systems for downconversion rely on lanthanide ions. The unique and rich energy level structures of these ions allow for efficient spectral conversion, including up- and downconversion processes mediated by resonant energy transfer between neighboring lanthanide ions Auzel , Wegh et al. Considering the energy levels of all lanthanides, as shown in the Dieke energy level diagram Dieke , Peijzel et al.
Also, cooperative sensitization is possible where energy transfer occurs from a high excited state of the donor to two neighboring acceptor ions without an intermediate level. Cooperative energy transfer from Tb to two Yb ions. The same efficient down conversion process was observed in other host lattices: Zhang et al.
Solar Spectrum Conversion for Photovoltaics Using Nanoparticles
Zhang et al. Cooperative downconversion for other couples of lanthanides was also claimed. For the couple Pr, Yb and Tm, Yb co-doped into borogermanate glasses a decrease of the emission from higher energy levels of Pr and Tm was observed Liu et al. The efficiency of the downconversion process was estimated from the decrease of the lifetime of the donor state.
Similar results were found for the Pr, Yb couple in aluminosilicate glasses Lakshminarayana et al.
More recent work on the Pr, Yb couple confirmed the presence of downconversion, but the mechanism involved was pointed out to be a resonant two-step energy transfer rather than a cooperative energy transfer Van der Ende et al. For the Pr, Yb couple an intermediate level 1 G 4 is available around 10, cm -1 , which makes a two-step resonant energy transfer process possible. This first-order process will have a much higher probability than the second-order cooperative transfer process.
An important aspect for downconversion is the incorporation in a solar cell. The solar spectrum has to be converted before entering the solar cell. A promising design is incorporation of downconverting material in a thin nm transparent layer on top of the solar cell.
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After downconversion the isotropically emitted nm need to be directed towards the solar cell. This can be achieved by a narrow-band reflective coating for nm NIR on top of the downconversion layer, thereby avoiding absorption in the other parts of the spectrum. Chen et al. Recent work on the Ce, Yb couple suggests that the energy transfer mechanism is not cooperative energy transfer, but single step energy transfer via a metal-to-metal charge transfer state.
Efficient downconversion for other lanthanide ion couples has been reported, including the Er, Yb couple in low phonon hosts Eilers et al. Research on new downconversion couples continues. It is not straightforward to establish the efficiency of the conversion to NIR photons and careful studies providing convincing evidence for the energy transfer mechanism and efficiency are required Van Wijngaarden Timmerman et al.
As also the original silicon NC relaxes from a highly excited state towards the lowest-energy excited state, the net result is two electron-hole pairs for each photon absorbed. Recent quantum yield measurements as a function of excitation wavelength confirmed the occurrence of carrier multiplication in Si nanocrystals Timmerman et al. Downshifting DS or photoluminescence is a property of many materials, and is similar to downconversion, however, only one photon is emitted and energy is lost due to non-radiative relaxation, see Fig. Therefore the quantum efficiency is lower than unity.
DS can be employed to overcome poor blue response of solar cells Hovel et al. Improvement of front passivation may make down shifters obsolete, or at least less beneficial. Downshifting layers can also be used to circumvent absorption of high-energy photons in heterojunction window layers, e. A recent review is presented by Klampaftis et al.
Downshifting was suggested in the s to be used in so-called luminescent solar concentrators LSCs that were attached on to a solar cell Garwin , Goetzberger and Greubel In these concentrators, organic dye molecules absorb incident light and re-emit this at a red-shifted wavelength. Internal reflection ensures collection of all the re-emitted light in the underlying solar cells. As the spectral sensitivity of silicon is higher in the red than in the blue, an increase in solar cell efficiency was expected.
Also, it was suggested to use a number of different organic dye molecules of which the re-emitted light was matched for optimal conversion by different solar cells. This is similar to using a stack of multiple solar cells, each sensitive to a different part of the solar spectrum. Nowadays, new organic dyes can have extremely high luminescence quantum efficiency LQE near unity and are available in a wide range of colors at better re-absorption properties that may provide necessary UV stability. Quantum dots QDs have been proposed for use in luminescent concentrators to replace organic dye molecules: the quantum dot concentrator Barnham et al.
Quantum dots are nanometer-sized semiconductor crystals of which the emission wavelength can be tuned by their size, as a result of quantum confinement Alivisatos , Gaponenko QDs have advantages over dyes in that: i their absorption spectra are far broader, extending into the UV, ii , their absorption properties may be tuned simply by the choice of nanocrystal size, and iii they are inherently more stable than organic dyes Bruchez Jr.
In this section:
Moreover, iv there is a further advantage in that the red-shift between absorption and luminescence is quantitatively related to the spread of QD sizes, which may be determined during the growth process, providing an additional strategy for minimizing losses due to re-absorption Barnham et al. Performance in LSCs has been modeled using thermodynamic as well as ray-trace models Burgers et al. Calculated efficiencies vary between 2. Alternatives for dye molecules used in LSCs are luminescent ions.
Traditionally, efficient luminescent materials rely on the efficient luminescence of transition metal ions and lanthanide ions. In case of transition metal ions intraconfigurational 3d n transitions are responsible for the luminescence, while in case of lanthanide ions both intraconfigurational 4f n -4f n transitions and interconfigurational 4f n -4f n-1 5d transitions are capable of efficient emission. In most applications efficient emission in the visible is required and emission from lanthanide ions and transition metal ions is responsible for almost all the light from artificial light sources e.
The optimum wavelength is between and nm, which is close to the band gap of c-Si and in the spectral region where c-Si solar cells have their optimum conversion efficiency. Two types of schemes can be utilized to achieve efficient conversion of visible light into narrow band NIR emission. A single ion can be used if the ion shows a strong broad band absorption in the visible spectral range followed by relaxation to the lowest excited state from which efficient narrow band or line emission in the NIR occurs.
Alternatively, a combination of two ions can be used where one ion the sensitizer absorbs the light and subsequently transfers the energy to a second ion the activator , which emits efficiently in the NIR. Both concepts have been investigated for LSCs by incorporating luminescent lanthanides and transition metal ions in glass matrices.
The stability of these systems is not a problem, in contrast to LSCs based on dye molecules, however, the quantum efficiency of luminescent ions in glasses appeared to be much lower than in crystalline compounds, especially in the infrared, thus hampering use for LSCs.
Chung et al. This protective coating can remain in place and down converters or shifters can easily be added. Svrcek et al. McIntosh et al. Mutlugun et al. However, the quality of their bare c-Si cells is very poor. Yuan et al.
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Stupca et al. The employed luminescent species has an absorption band around nm and a broad emission between and nm. Besides QDs, other materials have been suggested such as rare earth ions and dendrimers Serin et al. A maximum increase of For example, Goldschmidt et al. It was argued that the conversion efficiency was limited by the spectral range of the organic dyes used, and that if the same quantum efficiency as was reached for the nm range could be realized for the range nm an efficiency of They also discuss the benefits of a photonic structure on top of the plate, to reduce the escape cone loss Goldschmidt et al.
The proposed structure is a so-called rugate filter; this is characterized by a varying refractive index in contrast to standard Bragg reflectors, which suppresses the side loops that could lead to unwanted reflections. Slooff et al. The highest efficiency measured was 7. As stated above, quantum dots are potential candidates to replace organic dye molecules in an LSC, for their higher brightness, better stability, and wider absorption spectrum Barnham et al. They reported on the successful fabrication of thin silicon oxide films that contain CdS QDs using a sol-gel dip-coating process, whereby the nm sized CdS QDs are formed during thermal treatment after dip-coating.
Reda also prepared CdS QD concentrators, using sol-gel spin coating, followed by annealing. It is known that oxidation leads to blue-shifts in emission Van Sark et al. Blue-shifts have also been observed by Gallagher et al. Bomm et al. To one side of this plate, a mc-Si solar cell was placed, and aluminum mirrors to all other sides. Compared to the bare cell 5x0.
The QDC efficiency is 3.realsport.cl/wp-includes/2020-05-31/8297-contacto-con.php
Third generation photovoltaics : advanced solar energy conversion
However, re-absorption may still be a problem, as is demonstrated by a small red shift in the emission spectrum for long photon pathways; also absorption by the matrix is occurring. Hyldahl et al. They also used the organic dye Lumogen F Red, and obtained efficiency of 2. Upconversion was, like DC also suggested in the s, by Bloembergen , and was related to the development of IR detectors: IR photons would be detected through sequential absorption, as would be possible by the arrangement of energy levels of a solid.
However, as Auzel pointed out the essential role of energy transfer was only recognized nearly 20 years later. Schematic representation of two upconversion processes and the characteristic time response of the up converted emission after a short excitation pulse. This is a single ion process and takes place during the excitation pulse. This may explain that research in this field with focus on enhancing solar cell efficiency was started only recently Shalav et al. Upconverters usually combine an active ion, of which the energy level scheme is employed for absorption, and a host material, in which the active ion is embedded.