FR2792460A1 - Photovoltaic generator, having light cascades, comprises photovoltaic cell included in transparent matrix having dichroic filter on its entry surface and reflective coating on its opposite surface - Google Patents

Abstract

The present invention relates to a photovoltaic generator comprising at least one photovoltaic cell and a transparent matrix deposited with at least one optically active material having an absorption wavelength lambdaa and a reemission wavelength lambdar , the optically active material being chosen so that lambdaa corresponds to a range of lower sensitivity of the photovoltaic cell than lambdar , the matrix comprising a reflective coating. The matrix has on the input surface a dichroic filter substantially reflecting the wavelengths above approximately 950 nm, and substantially transparent for the wavelengths below 950 nm, and on the surface opposite the input surface a reflective coating for wavelengths above 400 nm, the photovoltaic cell being included in the transparent matrix.

Description

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  LIGHT CASCADE PHOTOVOLTAIC GENERATORS

  AND VARIATION OF ELECTROMAGNETIC FLOW.

  The present invention relates to the field of

photovoltaic conversion.

  Electric generators comprising photovoltaic cells are known in the prior art. These cells are made up of semiconductor barriers delivering an electrical signal

  function of the light intensity illuminating their surface.

  Various works have been carried out to improve the yield of

such cells.

  A first series of works concerns the improvement of the cells themselves, by the production of monocrystalline cells for example. These improvements result in cells whose cost of

  workmanship is extremely high.

  Another series of works focused on improving the conditions of cell illumination, in particular by techniques of conversion of the solar spectrum in order to optimally adapt the light radiation acting on the cells, to the curve of

sensitivity of these cells.

  American patent US4,110,123 describes for example a photovoltaic conversion device

  comprising a support doped with fluorescent materials.

  US patent US5813238 also describes a solar collector having long-lasting fluorescent properties comprising a polymer matrix, a dye, and a stabilizer. The polymer matrix is composed of polycarbonate and the dye is chosen from the group consisting essentially of thioxanthone, perylene imide and / or thioindigoide compounds. This patent proposes

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  also to position reflective elements so that the collected sunlight can be

directed to a solar cell.

  US Patent US4367367 describes a collector adapted to concentrate solar energy on a photoelectric cell comprising at least one fluorescent dopant. The cell is fixed to an edge of the collector, which is coated with a reflective coating. American patent US4395582 also describes a solar converter comprising a substrate doped with photoactive combinations called "light cascades", to improve the quality of the light spectrum.

  illuminating the photocells.

  The object of the invention is to propose an improved photovoltaic generator, having a yield

  high for a small footprint.

  To this end, the invention relates, according to its most general meaning, to a photovoltaic generator comprising at least one photovoltaic cell and a transparent matrix deposited with at least one optically active material having an absorption wavelength ka and a length of re-emission wave kr, the optically active material being chosen so that Xa corresponds to a range of lower sensitivity of the photovoltaic cell than kr, the matrix comprising a reflective coating, characterized in that the matrix has on the input surface a dichroic filter substantially reflecting wavelengths greater than about 950 nm, and substantially transparent for wavelengths less than 950 nm, and on the surface opposite to the input surface a reflective coating for longer wavelengths at 400 nm, the cell

  photovoltaic being included in the transparent matrix.

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  Advantageously, the matrix is formed by a strip of polymethyl methacrylate doped with light cascades. Preferably, the input surface of the matrix is coated with an interference layer has a maximum transmission rate for wavelengths between 330 and 900 nm and a reflection rate

  maximum for wavelengths greater than 950 nm.

  According to a preferred embodiment, the surface opposite to the entry surface of the matrix is coated with a diffusing reflective layer having a maximum reflection rate for wavelengths between 300 and 600 nm, a rate of high absorption for wavelengths of the order of 600 nm and a high diffusion rate for wavelengths

about 950 nm.

  According to a particular embodiment, the lateral zones of the matrix are coated with a reflective layer. According to a preferred embodiment, the generator according to the invention comprises a plurality of photovoltaic cells arranged in planes

  substantially perpendicular to the entry surface.

  The invention will be better understood on reading

  the following description, referring to the attached drawings

  o: - the single figure represents a view in

  perspective of a second example of embodiment.

  The single figure shows a sectional view of a generator according to the invention. It consists of a rectangular block (1) forming a transparent polymethyl methacrylate (PMMA) matrix. This matrix (1) is doped with light cascades, term designating compositions associating several materials

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  optically active and having a large offset between the absorption wavelength and the re-emission wavelength. These light cascades have the effect of mainly absorbing the wavelengths corresponding to the ranges of low sensitivity of the photovoltaic cells, and of high energy of the solar spectrum, and of shifting the energy towards wavelengths corresponding to ranges of high sensitivity of

photovoltaic cells.

  For example, the absorption takes place between 360 and 600 nm, and the re-emission takes place around 600 nm. The input surface (2) of the matrix is coated with a dichroic interference filter reflecting radiation of wavelength greater than 950 nm, and transparent for wavelengths between 330

nm and 900 nm.

  The opposite surface (3) as well as the lateral faces (4, 5, 6) are coated with a white reflector having an absorption peak around 600 nm and a peak of

re-emission around 950 nm.

  The matrix (1) also comprises a plurality of photovoltaic cells (7) arranged in

  planes (8 to 10) perpendicular to the entry surface (2).

  The cells are encapsulated in the matrix at the time of manufacture. Such a configuration makes it possible to increase the efficiency of the generator by a factor of 11 compared to a generator according to the state of the art,

  having an identical entry surface.

  The ratio between the input surface Sl and the cumulative surface S2 of the photovoltaic cells is

around 100.

  According to a variant, the cells are glued

  on certain lateral faces of the parallelepiped block.

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  It may also be advantageous to incorporate into the coating of the face opposite the illumination surface an anti-stoke dopant making it possible to pump light in the spectral band 1.4 to 1.6 micrometers and to reemit in the visible, for example between 550 and 660 nanometers. This dopant may be, for example, a rare earth, in particular a rare earth oxysulfide, and more particularly the product sold under the trade name of "LUMILUX Green UCZ" or the product "LUMILUX IR

  CD 142 "from RIEDEL from HAHN.

  The invention is described in the foregoing to

by way of nonlimiting example.

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Claims (7)

  1 - Photovoltaic generator comprising at least one photovoltaic cell and a transparent matrix deposited with at least one optically active material having an absorption wavelength Xa and a re-emission wavelength Krt, the optically active material being chosen so that K corresponds to a range of lesser sensitivity of the photovoltaic cell than Xr, the matrix comprising a reflecting coating, characterized in that the matrix has on the input surface a dichroic filter substantially reflecting wavelengths greater than 950 nm approximately, and substantially transparent for wavelengths below 950 nm, and on the surface opposite the input surface a reflective coating for wavelengths above 400 nm, the cell   photovoltaic being included in the transparent matrix.   2 - Photovoltaic generator according to claim 1 characterized in that the matrix is formed by a blade of polymethyl methacrylate doped with bright waterfalls.   3 - Photovoltaic generator according to claim 1 or 2 characterized in that the input surface of the matrix is coated with an interference layer has a maximum transmission rate for wavelengths between 330 and 900 nm and a rate maximum reflection for wavelengths greater than 950 nm.   4 - Photovoltaic generator according to claim 1, 2 or 3 characterized in that the surface 7 2792460   opposite to the entry surface of the matrix is coated with a diffusing reflective layer having a maximum reflection rate for wavelengths between 300 and 600 nm, a significant absorption rate for wavelengths of the order of 600 nm and a large diffuse re-emission for wavelengths of approximately 950 nm. Photovoltaic generator according to claim 1 characterized in that the lateral zones   of the matrix are coated with a reflective layer.   6 - Photovoltaic generator according to claim 1 characterized in that it comprises a plurality of photovoltaic cells arranged according to   planes substantially perpendicular to the entry surface.   7 - Photovoltaic generator according to claim 1 characterized in that the ratio between the input surface S1 and the cumulative surface S2 of the cells   photovoltaic is around 100.   8 - Photovoltaic generator according to one to   less of the preceding claims characterized in that   the illumination surface comprises an anti-stoke dopant making it possible to pump light in the spectral band 1.4 to 1.6 micrometers and to re-emit in the visible, by   example between 550 and 660 nanometers.