LUMINESCENT SOLAR CONCENTRATOR USING PEROVSKITE STRUCTURES

Abstract

A luminescent solar concentrator having a glass or plastics matrix containing or covered with perovskites having luminescence from intra-gap states is provided.

Claims

1. A luminescent solar concentrator having a body of polymer or glass material and comprising fluorophores, wherein said fluorophores are perovskite nanostructures doped or not doped with heteroatoms, with emission from intra-gap states.

2. The luminescent solar concentrator according to claim 1, wherein said nanostructures are alternatively of nanocrystalline, filament or two-dimensional or thin film shape.

3. The luminescent solar concentrator according to claim 1, wherein the perovskite nanostructures alternatively have compositions of the following type: A) M.sup.1M.sup.2X.sub.3 where: M.sup.1=an element in group IA or 1 in the IUPAC nomenclature; M.sup.2=Pb; X=element in group VII.sub.A or 17 in the IUPAC nomenclature, doped with heteroatoms; B) M.sup.1M.sup.2X.sub.3 where: M.sup.1=element in group IA or 1 in the IUPAC nomenclature, M.sup.2=element in group IV or 14 in the IUPAC nomenclature other than Pb; X=element in group VII.sub.A or 17 in the IUPAC nomenclature, undoped or doped with heteroatoms; C) M.sup.1.sub.2M.sup.2X.sub.6 where: M.sup.1=element in group IA or 1 in the IUPAC nomenclature; M.sup.2=element in group IV or 14 in the IUPAC nomenclature; X=element in group VII.sub.A or 17 in the IUPAC nomenclature, either undoped or doped with heteroatoms; D) MAM.sup.2X.sub.3 where: MA=[CH.sub.3NH.sub.3].sup.+, CH(NH.sub.2).sub.2].sup.+, [CH.sub.6N.sub.3].sup.+ or another organic cation; M.sup.2=element in group IV or 14 in the IUPAC nomenclature; X=element in group VII.sub.A or 17 in the IUPAC nomenclature, either undoped or doped with heteroatoms; E) M.sup.1.sub.3M.sup.2.sub.2X.sub.9 or MA.sub.3M.sup.2.sub.2X.sub.9 where: M.sup.1=element in group IA or 1 in the IUPAC nomenclature; M.sup.2=element in group V.sub.A or 15 in the IUPAC nomenclature; X=element in group VII.sub.A or 17 in the IUPAC nomenclature; and MA=[CH3NH3].sup.+, CH(NH.sup.2).sub.2].sup.+, [CH.sub.6N.sub.3].sup.+ or another organic cation, these structures being undoped or doped with heteroatoms.

4. The luminescent solar concentrator according to claim 1, wherein the nanostructures are double perovskites having a composition of the M.sup.1.sub.2M.sup.2M.sup.3X.sub.6 type where: M.sup.1=element in group IA or 1 in the IUPAC nomenclature; M.sup.2=elements in group IB or 11 in the IUPAC nomenclature or group IIIA or 13 in the IUPAC nomenclature; M.sup.3=element in group V.sub.A or 15 in the IUPAC nomenclature; and X=element in group VII.sub.A or 17 in the IUPAC nomenclature.

5. The luminescent solar concentrator according to claim 4, wherein the perovskite nanostructures are selected from the group consisting of: Cs.sub.2CuSbCl.sub.6, Cs.sub.2CuSbBr.sub.6, Cs.sub.2CuBiBr.sub.6, Cs.sub.2AgSbBr.sub.6, Cs.sub.2AgSbI.sub.6, Cs.sub.2AgBiI.sub.6, Cs.sub.2AuSbCl6, Cs.sub.2AuBiCl6, Cs.sub.2AuBiBr.sub.6, Cs.sub.2InSbCl.sub.6, Cs.sub.2InBiCl.sub.6, Cs.sub.2TlSbBr.sub.6, Cs.sub.2TlSbI.sub.6, and Cs.sub.2TlBiBr.sub.6, said nanostructures may be undoped or doped with heteroatoms.

6. The luminescent solar concentrator according to claim 1, wherein the perovskite nanostructures are structures of the type (C.sub.4N.sub.2H.sub.14Br).sub.4SnX.sub.6 where: X=Br, I or another element in group VII.sub.A or 17 in the IUPAC nomenclature.

7. The luminescent solar concentrator according to claim 1, wherein the body is made of at least one of the following polymers or corresponding copolymers: polyacrylates and polymethylmethacrylates, polyolefins, polyvinyls, epoxy resins, polycarbonates, polyacetates, polyamides, polyurethanes, polyketones, polyesters, polycyanoacrylates, silicones, polyglycols, polyimides, fluorinated and perfluorinated polymers, polycellulose and derivatives such as methyl-cellulose, hydroxymethyl-cellulose, polyoxazine, and silica-based glasses.

8. The luminescent solar concentrator according to claim 1, wherein said luminescent solar concentrator has a sheet-like shape in which the nanostructures are dispersed within a plastics or silica-based glass matrix or deposited in the form of a film on the surfaces thereof.

9. Window for buildings or for moving structures comprising at least a part constructed using a luminescent solar concentrator according to claim 1.

Description

[0013] For a better understanding of the present invention the following drawings are appended purely by way of anon-limiting example, and in these:

[0014] FIG. 1 shows a diagrammatical representation of a luminescent solar concentrator (LSC) comprising a polymer matrix incorporating perovskite nanocrystals doped with heteroatoms or having a suitable composition for obtaining intra-gap states which are not due to heteroatoms;

[0015] FIG. 2 shows a comparison between a diagram representing the energy levels of an undoped perovskite nanostructure and those of a perovskite nanostructure doped with a heteroatom (for example manganese) and of a composition such as to have optically active intra-gap energy levels, of both the donor and accepter type, used in an LSC according to the invention;

[0016] FIG. 3 shows the absorption spectrum (line A) and the photoluminescence spectrum (line P) of particular perovskite nanocrystals obtained according to the manner of implementation of the invention described;

[0017] FIG. 4 shows standardised luminescence spectra for the perovskite nanocrystals considered in FIG. 3 collected at the edges of a luminescent solar concentrator according to one embodiment of the invention; and

[0018] FIG. 5 shows the output power produced by photovoltaic cells located at the edges of the concentrator according to the invention.

[0019] With reference to the figures mentioned, a luminescent solar concentrator or LSC 1 comprises a body 1A made of glass or plastics or polymer material in which colloidal nanocrystals of perovskite are present, which for purely descriptive purposes are shown as clearly identifiable elements within body 1 of the concentrator. As is known, a nanocrystal or nanostructure is a structure having linear dimensions of the order of a nanometre (for example 10 nm) and in any event less than 100 nm. The nanocrystals or nanostructures NS present in LSC 1 are indicated by 2.

[0020] At the edges 3,4, 5,6 of body 1 there are photovoltaic cells 7 capable of collecting and converting the light radiation emitted by the NS present in body 1 (indicated by arrows Z) into electricity. The incident solar radiation on the body of the device is indicated by arrows F.

[0021] Body 1A of LSC 1 may be obtained from different materials. By way of a non-limiting example the latter may be: polyacrylates and polymethyl methacrylates, polyolefins, polyvinyls, epoxy resins, polycarbonates, polyacetates, polyamides, polyurethanes, polyketones, polyesters, polycyanoacrylates, silicones, polyglycols, polyimides, fluorinated polymers, polycellulose and derivatives such as methyl-cellulose, hydroxymethyl-cellulose, polyoxazine, silica-based glasses. The same body of the LSC may be obtained using copolymers of the abovementioned polymers.

[0022] The NS are able to exhibit photoluminescence efficiencies of almost 100% and an emission spectrum which can be selected through dimensional control and through composition or doping with heteroatoms, as a result of which they can be optimally incorporated into various types of solar cells comprising both single junction and multiple junction devices.

[0023] According to a fundamental characteristic of the present invention the colloidal nanostructures used as emitters or fluorophores in the LSC described are, purely by way of non-limiting example, perovskite NS having generic compositions of the type: 1) M.sup.1M.sup.2X.sub.3 (with M.sup.1=Cs, M.sup.2=Pb, X=element in group VII.sub.A or 17 in the IUPAC nomenclature) doped with heteroatoms; 2) M.sup.1M.sup.2X.sub.3 (with M.sup.1=Cs, M.sup.2=Sn or another element in group IV or 14 in the IUPAC nomenclature other than Pb; X=element in group VII.sub.A or 17 in the IUPAC nomenclature) which are not doped or doped with heteroatoms; 3) M.sup.1.sub.2M.sup.2X.sub.6 (with M.sup.1=Cs, M.sup.2=element in group IV or 14 in the IUPAC nomenclature, X=element in group VII.sub.A or 17 in the IUPAC nomenclature) either undoped or doped with heteroatoms; 4) MAM.sup.2X.sub.3 (with MA=[CH.sub.3NH.sub.3]+, [CH(NH.sub.2).sub.2]+, [CH.sub.6N.sub.3]+; M.sup.2=element in group IV or 14 in the IUPAC nomenclature, X=element in group VII.sub.A or 17 in the IUPAC nomenclature) either undoped or doped with heteroatoms; 5)M.sup.1.sub.3M.sup.2.sub.2X.sub.9 or MA.sub.3M.sup.2.sub.2X.sub.9 (with M.sup.1=Cs or another element in group IA or 1 in the IUPAC nomenclature, M.sub.2=Bi or another element in group V.sub.A or 15 in the IUPAC nomenclature) undoped or doped with heteroatoms; 6) double perovskites of generic composition M.sup.1.sub.2M.sup.2M.sup.3X.sub.6 (with M1=an element in group IA or 1 in the IUPAC nomenclature, M.sup.2=elements in group IB or 11 in the IUPAC nomenclature or group IIIA or 13 in the IUPAC nomenclature, M.sup.3=element in group V.sub.A or 15 in the IUPAC nomenclature, X=element in group VII.sub.A or 17 in the IUPAC nomenclature) such as, for example: Cs.sub.2CuSbCl.sub.6, Cs.sub.2CuSbBr.sub.6, Cs.sub.2CuBiBr.sub.6, Cs.sub.2AgSbBr.sub.6, Cs.sub.2AgSbI.sub.6, Cs.sub.2AgBiI.sub.6, Cs.sub.sAuSbCl.sub.6, Cs.sub.2AuBiCl.sub.6, Cs.sub.2AuBiBr.sub.6,

[0024] Cs.sub.2InSbCl.sub.6, Cs.sub.2InBiCl.sub.6, Cs.sub.2TlSbBr.sub.6, Cs.sub.2TlSbI.sub.6, and Cs.sub.2TlBiBr.sub.6. These structures may be undoped or doped with heteroatoms; 7) structures of the type (C.sub.4N.sub.2H.sub.14Br) .sub.4SnX.sub.6 (with X=Br, I or another element in group VII.sub.A or 17 in the IUPAC nomenclature).

[0025] In a case reported by way of example and to which FIGS. 2-5 refer, CsPbCl.sub.3 was specifically selected as the host material and manganese ions (Mn.sup.2+) as the doping agent, because in this system both the ground state (.sup.6A.sub.1) and the excited triplet state (.sup.4T.sub.1) of Mn.sup.2+ lie within the NS host energy gap, which results in more effective sensitisation of the doping agent by the NS host in comparison with all the other varieties of CsPbX.sub.3 having pure compositions and compositions mixed with halogens. What is fundamental for application in LSCs is the fact that the ground state and the excited states of Mn.sup.2+ have a multiplicity of different spins, determining the characteristic small extinction coefficient (approximately 1 M.sup.1 cm.sup.1) of the .sup.6A.sub.1.fwdarw..sup.4T.sub.1 absorption transition. This means that the corresponding luminescence indirectly excited by the host NS is essentially unaffected by reabsorption.

[0026] In one embodiment of the invention a nanocomposite LSC comprising a bulk-polymerised polyacrylate matrix incorporating perovskite NS of the abovementioned type was prepared and tested. Spectroscopic measurements of the NS in toluene solution and incorporated in the polymer wave guide indicate that the optical properties of the doping agent are completely preserved after the free-radical polymerisation process, further demonstrating the suitability of doped perovskite NS as emitters in nanocomposites of plastics material. Finally, light propagation measurements performed on the LSC confirm that the LSC device based on perovskite NS doped with Mn.sup.2+ essentially behaves as an ideal device without reabsorption or optical diffusion losses.

[0027] In one embodiment of the invention nanocrystals of CsPbCl.sub.3 perovskite with a Mn doping level of approximately 3.9% were used.

[0028] FIG. 3 shows the optical absorption spectrum (line A) and the photoluminescence spectrum (PL, graph P) of the nanocrystals with the characteristic absorption peak at approximately 395 nm and the corresponding narrow band photoluminescence at approximately 405 nm, representing approximately 20% of the total emission. The remaining 80% of the emitted photons are due to the .sup.4T.sub.1.fwdarw..sup.6A.sub.1 optical transition of the Mn.sup.2+ doping agents, which give rise to the peak at approximately 590 nm, with a consequent high Stokes shift of approximately 200 nm (approximately 1 eV) from the absorption edge of the CsPbCl3 host nanocrystal.

[0029] Examination of the spectrum in FIG. 4 shows that the luminescence of the Mn.sup.2+ is almost completely uninfluenced by reabsorption by the host nanocrystal.

[0030] By way of example, a luminescent solar concentrator or LSC 1 was constructed using bulk polymerisation with free radical initiators of a mixture of methylmethacrylate (MMA) and lauryl methacrylate (LMA) doped with nanocrystals having a percentage by weight of 80% of MMA and 20% of LMA (obviously other percentages by weight are possible).

[0031] LSC 1 was obtained with dimensions of 25 cm 20 cm0.5 cm and comprising 0.03% by weight of nanocrystals.

[0032] FIG. 4 shows the standardised luminescence spectra for manganese emission in CsPbCl.sub.3 nanocrystals collected from photovoltaic cells 7 present at the edges of the luminescent solar concentrator under local excitation at an increasing distance from the edge of the sheet. The spectra are essentially identical, indicating that there are no distortional effects due to optical absorption.

[0033] Further confirmation of the absence of reabsorption and optical diffusion losses in the LSC is provided by the fact that all the portions of the surface of the device contribute almost equally to the total power collected at its edges. To show this behaviour FIG. 5 shows the relative output power extracted from one of the edges of the LSC (edge dimensions having an area of 200.5 cm.sup.2) measured using calibrated crystalline Si solar cells attached to one edge of the sheet and progressively exposing increasingly larger portions of the area of the LSC to solar radiation.

[0034] FIG. 5 shows a graph or line C relating to a theoretically calculated power for an ideal LSC without diffusion or reabsorption losses and having identical dimensions to the one constructed experimentally (25 cm20 cm0.5 cm); said ideal LSC includes emitters having the same quantum emission yield of the Mn.sup.2+ used in the nanocrystals of LSC 1. For the ideal LSC the output optical power is determined exclusively by the numerical aperture of the illuminated area. The experimental data, also shown in FIG. 5, almost perfectly overlap with the calculated data.

[0035] Thanks to the invention the suitability of perovskite nanostructures with emission from intra-gap states due in the case in the example to the use of doping agents as emitters with virtually zero reabsorption in luminescent solar concentrators has been demonstrated.