Ferroelectric enhanced solar cell and preparation method thereof

Abstract

A ferroelectric enhanced solar cell, including a conductive substrate, and a hole blocking layer, a mesoporous nanocrystalline layer, a mesoporous spacer layer and a mesoporous back electrode sequentially deposited in that order on the conductive substrate. The mesopores of at least one of the mesoporous nanocrystalline layer, the mesoporous spacer layer and the mesoporous back electrode are filled with a photoactive material. At least one of the hole blocking layer, the mesoporous nanocrystalline layer and the mesoporous spacer layer includes a ferroelectric material or a ferroelectric nanocomposite.

Claims

1. A solar cell, comprising: a conductive substrate; and a hole blocking layer, a mesoporous nanocrystalline layer, a mesoporous spacer layer and a mesoporous back electrode which are sequentially deposited in that order on the conductive substrate; wherein: mesopores of at least one of the mesoporous nanocrystalline layer, the mesoporous spacer layer and the mesoporous back electrode are filled with a photoactive material; and at least one of the hole blocking layer, the mesoporous nanocrystalline layer and the mesoporous spacer layer comprises a ferroelectric material or a ferroelectric nanocomposite.

2. The solar cell of claim 1, wherein: when the hole blocking layer comprises the ferroelectric material or the ferroelectric nanocomposite, the hole blocking layer has a thickness of not more than 100 nm; when the mesoporous nanocrystalline layer comprises the ferroelectric material or the ferroelectric nanocomposite, the mesoporous nanocrystalline layer has a thickness of 100 nm to 5000 nm; and when the mesoporous spacer layer comprises the ferroelectric material or the ferroelectric nanocomposite, the mesoporous spacer layer has a thickness of 100 nm to 5000 nm.

3. The solar cell of claim 1, wherein the ferroelectric material is a dielectric material; the ferroelectric materials in the hole blocking layer and the mesoporous nanocrystalline layer are BaSnO.sub.3, and the ferroelectric material in the mesoporous spacer layer is one or more of CaTiO.sub.3, BaTiO.sub.3, PbZrO.sub.3, PbTiO.sub.3, PbZrO.sub.3, ZnTiO.sub.3, BaZrO.sub.3, Pb(Zr.sub.1-xTi.sub.x)O.sub.3, (La.sub.yPb.sub.1-y)(Zr.sub.1-xTi.sub.x)O.sub.3, (1−x)[Pb(Mg.sub.1/3Nb.sub.2/3)O.sub.3].x[PbTiO.sub.3], BiFeO.sub.3, Pb(Zn.sub.1/3Nb.sub.2/3)O.sub.3, Pb(Mg.sub.1/3Nb.sub.2/3)O.sub.3, (Na.sub.1/2Bi.sub.1/2)TiO.sub.3, (K.sub.1/2Bi.sub.1/2)TiO.sub.3, LiNbO.sub.3, KNbO.sub.3, KTaO.sub.3, Pb(Sr.sub.xTa.sub.1-x)O.sub.3 and Ba.sub.xSr.sub.1-xTiO.sub.3; wherein x in Pb(Zr.sub.1-xTi.sub.x)O.sub.3 and (1−x)[Pb(Mg.sub.1/3Nb.sub.2/3)O.sub.3].x[PbTiO.sub.3] satisfies 0≤x≤1; in (La.sub.yPb.sub.1-y)(Zr.sub.1-xTi.sub.x)O.sub.3, x satisfies 0≤x≤1, and y satisfies 0≤y≤1; x in Pb(Sr.sub.xTa.sub.1-x)O.sub.3 satisfies 0≤x≤1; x in Ba.sub.xSr.sub.1-xTiO.sub.3 satisfies 0≤x≤1; and the ferroelectric material of the mesoporous nanocrystalline layer or the mesoporous spacer layer has a particle size of 5 to 200 nm.

4. The solar cell of claim 1, wherein the ferroelectric nanocomposite has a core-shell structure with ferroelectric material nanoparticles as a core and an insulating material as a shell; the insulating material is at least one of ZrO.sub.2, Al.sub.2O.sub.3 and SiO.sub.2; the ferroelectric materials of the hole blocking layer and the mesoporous nanocrystalline layer are BaSnO.sub.3, and the ferroelectric material of the mesoporous spacer layer is one or more of CaTiO.sub.3, BaTiO.sub.3, PbZrO.sub.3, PbTiO.sub.3, PbZrO.sub.3, ZnTiO.sub.3, BaZrO.sub.3, Pb(Zr.sub.1-xTi.sub.x)O.sub.3, (La.sub.yPb.sub.1-y)(Zr.sub.1-xTi.sub.x)O.sub.3, (1−x)[Pb(Mg.sub.1/3Nb.sub.2/3)O.sub.3].x[PbTiO.sub.3], BiFeO.sub.3, Pb(Zn.sub.1/3Nb.sub.2/3)O.sub.3, Pb(Mg.sub.1/3Nb.sub.2/3)O.sub.3, (Na.sub.1/2Bi.sub.1/2)TiO.sub.3, (K.sub.1/2Bi.sub.1/2)TiO.sub.3, LiNbO.sub.3, KNbO.sub.3, KTaO.sub.3, Pb(Sr.sub.xTa.sub.1-x)O.sub.3 and Ba.sub.xSr.sub.1-xTiO.sub.3; wherein x in Pb(Zr.sub.1-xTi.sub.x)O.sub.3 and (1−x)[Pb(Mg.sub.1/3Nb.sub.2/3)O.sub.3].x[PbTiO.sub.3] satisfies 0≤x≤1; in (La.sub.yPb.sub.1-y)(Zr.sub.1-xTi.sub.x)O.sub.3, x satisfies 0≤x≤1, and y satisfies 0≤y≤1; x in Pb(Sr.sub.xTa.sub.1-x)O.sub.3 satisfies 0≤x≤1; x in Ba.sub.xSr.sub.1-xTiO.sub.3 satisfies 0≤x≤1; and the ferroelectric nanocomposite of the mesoporous nanocrystalline layer or the mesoporous spacer layer has a particle size of 5 to 200 nm.

5. The solar cell of claim 1, wherein the hole blocking layer is a film of inorganic oxide semiconductor material or a film of ferroelectric material; and the inorganic oxide semiconductor material is TiO.sub.2, ZnO or SnO.sub.2.

6. The solar cell of claim 1, wherein the mesoporous nanocrystalline layer is a mesoporous TiO.sub.2 nanocrystalline layer, a mesoporous ZnO nanocrystalline layer, a mesoporous SnO.sub.2 nanocrystalline layer, a mesoporous ferroelectric material nanocrystalline layer or a mesoporous ferroelectric nanocomposite nanocrystalline layer; and the mesoporous nanocrystalline layer is a mesoporous BaSnO.sub.3 nanocrystalline layer.

7. The solar cell of claim 1, wherein the mesoporous spacer layer is a mesoporous ZrO.sub.2 layer, a mesoporous SiO.sub.2 layer, a mesoporous Al.sub.2O.sub.3 layer, a mesoporous ferroelectric material layer, or a mesoporous ferroelectric nanocomposite layer.

8. The solar cell of claim 1, wherein the photoactive material is a perovskite-type semiconductor material or a semiconductor material having a band gap of not more than 2 eV; the perovskite-type semiconductor material has a chemical formula of ABX.sub.3, where A is at least one of methylamine, formamidine and an alkali metal element, B is at least one of lead and tin, and X is at least one of iodine, bromine and chlorine; the narrow band gap semiconductor material is at least one of Se, SbSe, and CdSe.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The disclosure is described hereinbelow with reference to accompanying drawings, in which the sole FIGURE is a schematic structural diagram of a ferroelectric enhanced solar cell according to one embodiment of the disclosure.

(2) In the drawings, the following reference number are used: 1: conductive substrate, 2: hole blocking layer, 3: nanocrystalline layer, 4: mesoporous spacer layer, 5: mesoporous back electrode.

DETAILED DESCRIPTION

(3) To further illustrate, embodiments detailing a ferroelectric enhanced solar cell and a preparation method thereof are described below. It should be noted that the following embodiments are intended to describe and not to limit the disclosure.

EXAMPLE 1

(4) Perovskite Solar Cell with a Mesoporous Spacer Layer Comprising Pb(Zr.sub.xTi.sub.1-x)O.sub.3

(5) In the device, a conductive glass (such as a transparent conductive glass, for example, FTO) was used as a conductive substrate 1, and after a dense titanium dioxide layer 2 with a thickness of 50 nm was deposited on the conductive substrate 1, a titanium dioxide nanocrystalline layer 3, a mesoporous spacer layer 4 and a mesoporous back electrode 5 were sequentially deposited on the dense titanium dioxide layer 2 from bottom to top by screen printing and sintering (for example, 500° C.). Then, a positive electrode was connected to the FTO conductive substrate, and a negative electrode was connected to the mesoporous back electrode. Under the condition that the electric field has a field intensity of, for example, 2.5 kV/mm and a direction directed from the conductive substrate to the mesoporous back electrode layer, polarization was performed at 80° C. for a period of time (for example, 20 min).

(6) The titanium dioxide nanocrystalline layer may have a grain size of 18 nm and a thickness of about 1 μm, and may also has a grain size of 20 nm and a thickness of about 1 μm, for example. The mesoporous spacer layer is a Pb(Zr.sub.xTi.sub.1-x)O.sub.3 mesoporous spacer layer (x may take any value in the range of 0 to 1) or a ZrO.sub.2 mesoporous spacer layer. A slurry having a certain viscosity was prepared by mixing uniform stable Pb(Zr.sub.xTi.sub.1-x)O.sub.3 nanoparticles (having a particle size of, for example, 30 nm) or ZrO.sub.2 nanoparticles (having a particle size of, for example, 30 nm) with ethyl cellulose and terpineol in a mass ratio of 1:1:5, and then sintered (at, for example, 400 to 500° C.) after screen printing to remove the ethyl cellulose so as to obtain a film with a mesoporous structure, thereby forming a mesoporous spacer layer having a thickness of, for example, about 1 μm. The mesoporous back electrode is a mesoporous conductive film comprising graphite or carbon black, and has a thickness of, for example, about 10 μm. A certain amount (for example, 4 μL) of lead iodide methylamine (CH.sub.3NH.sub.3Pbl.sub.3) precursor solution (30 wt %) was applied dropwise onto the mesoporous back electrode, allowed to stand for 10 minutes, and then dried at, for example, 100° C. The test shows that under simulated sunlight of 100 mW*cm.sup.−2, when the mesoporous spacer layer is made of Pb(Zr.sub.xTi.sub.1-x)O.sub.3, the photoelectric conversion efficiency of the unpolarized device is 9.77% and the photoelectric conversion efficiency of the polarized device is 11.03%; when the mesoporous spacer layer is made of ZrO.sub.2, the photoelectric conversion efficiencies of the unpolarized and polarized devices are respectively 8.54% and 8.51%.

EXAMPLE 2

(7) Perovskite Solar Cell with a Mesoporous Nanocrystalline Layer Comprising BaSnO.sub.3

(8) In the device, a conductive glass was used as a conductive substrate 1, and after a dense titanium dioxide layer 2 with a thickness of, for example, 50 nm was deposited on the conductive substrate 1, a nanocrystalline layer 3, a mesoporous spacer layer 4 and a mesoporous back electrode 5 were sequentially deposited on the dense titanium dioxide layer 2 from bottom to top by screen printing and sintering (for example, 400° C.). Then, a positive electrode was connected to the FTO conductive substrate, a negative electrode was connected to the mesoporous back electrode. Under the condition that the electric field has a field intensity of, for example, 1.5 kV/mm, polarization was performed at 80° C. for a period of time (for example, 20 min) (the higher the temperature of the polarization environment, the smaller the required polarization field intensity).

(9) The mesoporous nanocrystalline layer is a BaSnO.sub.3 mesoporous nanocrystalline layer or a TiO.sub.2 mesoporous nanocrystalline layer. A slurry having a certain viscosity was prepared by mixing uniform stable BaSnO.sub.3 nanoparticles (having a particle size of, for example, 30 nm) or TO.sub.2 nanoparticles (having a particle size of, for example, 30 nm) with ethyl cellulose and terpineol in a mass ratio of 1:2:7, and then sintered after screen printing to form a film with a thickness of, for example, about 800 nm. The mesoporous spacer layer has a ZrO.sub.2 grain size of 20 nm and a thickness of about 2 μm, for example. The mesoporous back electrode is a mesoporous conductive film comprising graphite or carbon black, and has a thickness of, for example, about 10 μm. A certain amount (for example, 4 μL) of lead iodide methylamine (CH.sub.3NH.sub.3Pbl.sub.3) precursor solution (30 wt %) was applied dropwise onto the mesoporous back electrode, allowed to stand for 10 minutes, and then dried at, for example, 100° C. The test shows that under simulated sunlight of 100 mW*cm.sup.−2, when the mesoporous nanocrystalline layer is made of BaSnO.sub.3, the photoelectric conversion efficiency of the unpolarized device is 10.60% and the photoelectric conversion efficiency of the polarized device is 11.34%; when the mesoporous spacer layer is made of TiO.sub.2, the photoelectric conversion efficiencies of the unpolarized and polarized devices are respectively 10.10% and 10.15%.

EXAMPLE 3

(10) Perovskite Solar Cell with a Mesoporous Nanocrystalline Layer Comprising BaSnO.sub.3 and a Mesoporous Spacer Layer Comprising Pb(Zr.sub.xTi.sub.1-x)O.sub.3

(11) In the device, a conductive glass was used as a conductive substrate 1, and after a dense titanium dioxide layer 2 with a thickness of, for example, 30 nm was deposited on the conductive substrate 1, a BaSnO.sub.3 nanocrystalline layer 3, a Pb(Zr.sub.xTi.sub.1-x)O.sub.3 mesoporous spacer layer 4 and a mesoporous back electrode 5 were sequentially deposited on the dense titanium dioxide layer 2 from bottom to top by screen printing and sintering (for example, 500° C.). Then, a positive electrode was connected to the FTO conductive substrate, and a negative electrode was connected to the mesoporous back electrode. Under the condition that the electric field has a field intensity of, for example, 4.5 kV/mm, polarization was performed at 120° C. for a period of time (for example, 20 min).

(12) A slurry having a certain viscosity was prepared by mixing uniform stable BaSnO.sub.3 nanoparticles (having a particle size of, for example, 30 nm) with ethyl cellulose and terpineol in a mass ratio of 1:2:7, and then sintered after screen printing to form a BaSnO.sub.3 mesoporous nanocrystalline layer with a thickness of, for example, about 800 nm. A slurry having a certain viscosity was prepared by mixing uniform stable Pb(Zr.sub.xTi.sub.1-x)O.sub.3 nanoparticles (having a particle size of, for example, 30 nm) with ethyl cellulose and terpineol in a mass ratio of 1:1:5, and then sintered after screen printing to form a Pb(Zr.sub.xTi.sub.1-x)O.sub.3 mesoporous nanocrystalline layer with a thickness of, for example, about 1 μm. The mesoporous back electrode is a mesoporous conductive film comprising graphite or carbon black, and has a thickness of, for example, about 10 μm. A certain amount (for example, 4 μL) of lead iodide methylamine (CH.sub.3NH.sub.3Pbl.sub.3) precursor solution (30 wt %) was applied dropwise onto the mesoporous back electrode, allowed to stand for 10 minutes, and then dried at, for example, 100° C. The test shows that under simulated sunlight of 100 mW*cm.sup.−2, the photoelectric conversion efficiency of the unpolarized device is 10.06% and the photoelectric conversion efficiency of the polarized device is 11.76%.

EXAMPLE 4

(13) Perovskite Solar Cell with a Mesoporous Spacer Layer Comprising ZrO.sub.2 Wrapped Pb(Zr.sub.xTi.sub.1-x)O.sub.3 Nanocomposite

(14) In the device, a conductive glass was used as a conductive substrate 1, and after a dense titanium dioxide layer 2 with a thickness of, for example, 50 nm was deposited on the conductive substrate 1, a titanium dioxide nanocrystalline layer 3, a ZrO.sub.2 wrapped Pb(Zr.sub.xTi.sub.1-x)O.sub.3 mesoporous spacer layer 4 and a mesoporous back electrode 5 were sequentially deposited on the dense titanium dioxide layer 2 from bottom to top by screen printing and sintering (for example, 500° C.). Then, a positive electrode was connected to the FTO conductive substrate, and a negative electrode was connected to the mesoporous back electrode. Under the condition that the electric field has a field intensity of, for example, 3.5 kV/mm, polarization was performed at 200° C. for a period of time (for example, 20 min).

(15) The titanium dioxide nanocrystalline layer may have a grain size of 18 nm and a thickness of about 1 μm, and may also has a grain size of 20 nm and a thickness of 800 nm, for example. The mesoporous spacer layer is a ZrO.sub.2 wrapped Pb(Zr.sub.xTi.sub.1-x)O.sub.3 mesoporous spacer layer or a ZrO.sub.2 mesoporous spacer layer. A slurry having a certain viscosity was prepared by mixing uniform stable ZrO.sub.2 wrapped Pb(Zr.sub.xTi.sub.1-x)O.sub.3 nanocomposite particles (i.e., core-shell composite particles with ZrO.sub.2 as a shell and Pb(Zr.sub.xTi.sub.1-x)O.sub.3 as a core, the particle size of the core-shell composite particle as a whole is 30 nm) or ZrO.sub.2 nanoparticles (having a particle size of, for example, 30 nm) with ethyl cellulose and terpineol in a mass ratio of 1:1:5, and then sintered after screen printing to form a mesoporous spacer layer with a thickness of, for example, about 2 μm. The mesoporous back electrode is a mesoporous conductive film comprising graphite or carbon black, and has a thickness of, for example, about 10 μm. A certain amount (for example, 4 μL) of lead iodide methylamine (CH.sub.3NH.sub.3Pbl.sub.3) precursor solution (30 wt %) was applied dropwise to the mesoporous back electrode, allowed to stand for 10 minutes, and then dried at, for example, 100° C. The test shows that under simulated sunlight of 100 mW*cm.sup.−2, when the mesoporous spacer layer is made of ZrO.sub.2 wrapped Pb(Zr.sub.xTi.sub.1-x)O.sub.3, the photoelectric conversion efficiency of the unpolarized device is 9.56% and the photoelectric conversion efficiency of the polarized device is 11.77%; when the mesoporous spacer layer is made of ZrO.sub.2, the photoelectric conversion efficiencies of the unpolarized and polarized devices are respectively 8.54% and 8.51%.

(16) In each of the above embodiments, the conductive substrate may preferably be a conductive glass or a conductive plastic, and the hole blocking layer 2 is an inorganic oxide film having good hole blocking ability, and is preferably a dense titanium oxide film or a tin oxide film which preferably has a thickness of 30 nm. However, the hole blocking layer 2 is not limited to the above two films, and its thickness can be adjusted as needed (for example, 10 to 50 nm). The material of the mesoporous nanocrystalline layer 3 comprises at least one of TiO.sub.2, ZnO, SnO.sub.2, BaSnO.sub.3, BaTiO.sub.3, (Na.sub.xBi.sub.1-x)TiO.sub.3, (K.sub.xBi.sub.1-x)TiO.sub.3 and a nanocomposite comprising the above materials, the grain size is not limited to 18 nm or 30 nm and may be selected as needed (for example, 20 to 100 nm), and the thickness is also not limited to that in the above embodiments (for example, 0.5 to 2 μm). The material of the mesoporous spacer layer comprises one or more of ZrO.sub.2, SiO.sub.2, Al.sub.2O.sub.3, CaTiO.sub.3, BaTiO.sub.3, PbZrO.sub.3, PbTiO.sub.3, PbZrO.sub.3, ZnTiO.sub.3, BaZrO.sub.3, Pb(Zr.sub.1-xTi.sub.x)O.sub.3, (La.sub.yPb.sub.1-y)(Zr.sub.1-xTi.sub.x)O.sub.3, (1−x)[Pb(Mg.sub.1/3Nb.sub.2/3)O.sub.3].x[PbTiO.sub.3], BiFeO.sub.3, Pb(Zn.sub.1/3Nb.sub.2/3)O.sub.3, Pb(Mg.sub.1/3Nb.sub.2/3)O.sub.3, (Na.sub.1/2Bi.sub.1/2)TiO.sub.3, (K.sub.1/2Bi.sub.1/2)TiO.sub.3, LiNbO.sub.3, KNbO.sub.3, KTaO.sub.3, Pb(Sr.sub.xTa.sub.1-x)O.sub.3, Ba.sub.xSr.sub.1-xTiO.sub.3 and a nanocomposite comprising the above materials, the particle size is not limited to that in the above embodiments and may be selected as needed (for example, 10 to 100 nm), and the thickness can also be adjusted in a range of 1 to 4 μm. The mesoporous back electrode 5 is preferably a carbon electrode or comprising high work function material such as indium tin oxide, but not limited to the above two types of back electrodes. The photoactive material is not limited to the perovskite-type semiconductor material of lead iodide methylamine (CH.sub.3NH.sub.3Pbl.sub.3) given in the embodiments, and all perovskite-type photoactive materials with the general formula ABX.sub.3 satisfy the conditions, wherein A is at least one of methylamine, formamidine and an alkali metal element, B is at least one of lead and tin, and X is at least one of iodine, bromine and chlorine; narrow band gap photoactive materials such as Se, SbSe and CdSe are also comprised, in addition to the perovskite-type photoactive materials.

(17) The mesoporous material, the nanocrystalline material and the like in the disclosure satisfy the conventional definition in the art, that is, the mesoporous material refers to a kind of porous material having a pore diameter of 2 to 100 nm, and the nanocrystalline material refers to a nanomaterial having a crystal structure and a size of 1 to 100 nm.

(18) In the above embodiments, sintering may be conducted once for deposition of each layer, or sintering may be conducted once for deposition of multiple layers (such as two or more layers). For example, sintering is performed once when the mesoporous nanocrystalline layer is deposited, and then sintering is performed once when the mesoporous spacer layer and the mesoporous back electrode layer are deposited. The ambient temperature at which the polarization is carried out, as well as the magnitude and direction of the electric field intensity of the applied electric field, may be flexibly adjusted according to actual conditions (such as the thickness and type of the ferroelectric material layer), as long as the ambient temperature is 80° C. to 150° C., the electric field intensity satisfies E≤10 kV/mm, and the direction of the electric field is perpendicular to the plane of the conductive substrate and directed from the mesoporous nanocrystalline layer to the mesoporous back electrode layer.

(19) The photoactive material in the disclosure may be a light absorbing semiconductor material, and may also be an organic material having photosensitive properties (corresponding to an organic solar cell), a photosensitive dye (corresponding to a dye-sensitized solar cell) or the like, in addition to the perovskite-type semiconductor material (corresponding to a perovskite solar cell). In the preparation process, the photoactive material precursor solution may be applied dropwise onto the frame structure of the polarized solar cell (i.e., applied dropwise onto the polarized mesoporous back electrode layer), so that the precursor solution is sequentially filled in nanopores of the mesoporous back electrode, the mesoporous spacer layer and the mesoporous nanocrystalline layer from top to bottom. Taking a mesoporous nanocrystalline layer filled with a photoactive material as an example, after being filled with a photoactive material (such as a perovskite-type semiconductor material or a narrow band gap semiconductor material), the mesoporous nanocrystalline layer becomes a photoactive layer. The dense hole blocking layer (i.e., an electron transport layer) may be, for example, a dense titanium oxide film, a dense tin oxide film, a dense zinc oxide film, or a dense ferroelectric material or ferroelectric nanocomposite film.

(20) In the ferroelectric enhanced solar cell of the disclosure, at least one of the hole blocking layer, the mesoporous nanocrystalline layer and the mesoporous spacer layer is composed of a ferroelectric material or a ferroelectric nanocomposite. In addition to the specific settings in the above embodiments, the thickness of each layer may be adjusted according to the needs of the cell; preferably, the hole blocking layer composed of the ferroelectric material or the ferroelectric nanocomposite has a thickness of not more than 100 nm (particularly preferably not more than 50 nm), the mesoporous nanocrystalline layer composed of the ferroelectric material or the ferroelectric nanocomposite has a thickness of 100 nm to 5000 nm (particularly preferably 500 nm to 1000 nm); the mesoporous spacer layer composed of the ferroelectric material or the ferroelectric nanocomposite has a thickness of 100 nm to 5000 nm (particularly preferably from 1 to 3 μm). It is possible to introduce a hole blocking layer, a mesoporous nanocrystalline layer or a mesoporous spacer layer composed of a ferroelectric material or a ferroelectric nanocomposite, and the preparation methods thereof can be obtained referring to the prior art, in which parameter conditions in the preparation methods can also be flexibly adjusted according to the thickness requirements of the respective layers. In the ferroelectric enhanced solar cell, the overall energy band structure needs to meet the requirements in the overall energy band of the solar cell in the prior art. Taking the spacer layer as an example, the purpose of the spacer layer is to prevent electrons from being transmitted to the mesoporous back electrode. Therefore, the conduction band of the material of the spacer layer should be higher than that of the photoactive material (such as a perovskite-type photoactive material), and in the ferroelectric material in the disclosure, such as Pb(Zr.sub.1-xTi.sub.x)O.sub.3, (1−x)[Pb(Mg.sub.1/3Nb.sub.2/3)O.sub.3].x[PbTiO.sub.3] and the like, x ranges from 0 to 1, which satisfies the energy band requirements of the corresponding ferroelectric material as the spacer layer. A separate dense ferroelectric material film can be used as a hole blocking layer. For example, in a case where the photoactive material is a perovskite-type semiconductor material, when a ferroelectric material has a suitable energy band (that is, the conduction band is lower than that of the perovskite-type light absorbing material, and the valence band is also lower than that of the perovskite-type light absorbing material), and also has good electrical conductivity, this ferroelectric material can be used as a hole blocking layer and an electron transport layer; for example, the BaSnO.sub.3 ferroelectric material can be deposited into a very thin dense film to serve as a hole blocking layer. In the disclosure, the ferroelectric material and the ferroelectric nanocomposite (that is, a composite having a core-shell structure with ferroelectric material nanoparticles as the core and the insulating material as the shell) preferably have a particle diameter of 5 to 200 nm (more preferably 20 to 50 nm), to form a spacer layer or a nanocrystalline layer having a mesoporous structure.

(21) It will be obvious to those skilled in the art that changes and modifications may be made, and therefore, the aim in the appended claims is to cover all such changes and modifications.