A ferroelectric photovoltaic device based on the shielding effect regulated by a dielectric insulating layer and its fabrication method.

Abstract

This invention discloses a ferroelectric photovoltaic device and its fabrication method based on the shielding effect regulated by a dielectric insulating layer, belonging to the field of ferroelectric photovoltaic device technology. The ferroelectric photovoltaic device based on the shielding effect regulated by a dielectric insulating layer comprises, from bottom to top, a substrate, a bottom electrode layer, a dielectric insulating layer, a photoelectric ferroelectric functional layer, and a top electrode layer; the dielectric insulating layer is an Al2O3 layer; the photoelectric ferroelectric functional layer is a hexagonal LuMnO3 single crystal layer. This invention utilizes the high dielectric constant Al2O3 dielectric insulating layer to form a mirror shield against external free charges, weakening the compensation of interface induced charges on the ferroelectric residual polarization, thereby regulating the ferroelectric depolarization field and thus controlling the photovoltaic effect; simultaneously, the dielectric insulating layer can effectively block carrier injection, suppress leakage current, reduce dark current, and thus increase the photoelectric response of the device.

Description

Technical Field

[0001] This invention relates to the field of ferroelectric photovoltaic device technology, and in particular to a ferroelectric photovoltaic device based on the shielding effect regulated by a dielectric insulating layer and its preparation method. Background Technology

[0002] Ferroelectric materials exhibit significant application potential in the optoelectronic field due to their bulk photovoltaic potential and photovoltaic response that can reverse with ferroelectric polarization reversal. Unlike traditional photovoltaic devices (such as PN junction diodes), which rely on the built-in electric field at the interface (E0), ferroelectric materials possess remarkable advantages. bi Unlike the separation of photogenerated carriers, the bulk photovoltaic effect (BPVE, non-interface origin) in non-centrosymmetric materials such as photoferroelectrics (BaTiO3, BiFeO3, etc.) can spontaneously generate a photogenerated short-circuit current (I0) through lattice symmetry breaking, allowing electron-hole pairs to spontaneously form photogenerated short-circuit currents (I0). SC Furthermore, optoferroelectrics exhibit reversible remanent polarization (P). r This generates a depolarization field (E) that permeates the interior and surface of the material. d This internal electric field can effectively separate photogenerated electron-hole pairs, and its photoelectric response can be reversed with the reversal of the ferropolarization / depolarization field. At this time, the photogenerated open-circuit voltage (V0) of the material... OC It is no longer limited by the semiconductor bandgap and the Shockley-Queisser limit of energy conversion efficiency.

[0003] However, the space-induced charge on the electrode surface, and the free carriers and defect charges inside the material, will redistribute within the picosecond to nanosecond range, affecting P r This creates dielectric shielding, making E d Rapid degradation. Experiments have shown that when ferroelectric thin films are directly exposed to the atmosphere or in contact with highly conductive substrates (such as heavily doped Si), their surface potential decreases by 50-80%, and the photocurrent gain decreases by more than an order of magnitude. Therefore, how to controllably "deshield" or "retune" the internal electric field is key to improving the photoelectric response of photoferroelectrics and obtaining high-performance ferroelectric photovoltaic devices. Summary of the Invention

[0004] The purpose of this invention is to provide a ferroelectric photovoltaic device and its fabrication method based on the shielding effect regulated by a dielectric insulating layer, so as to solve the problems existing in the prior art.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] One of the technical solutions of the present invention is a ferroelectric photovoltaic device based on the shielding effect regulated by a dielectric insulating layer, comprising a substrate, a bottom electrode layer, a dielectric insulating layer, a photoferroelectric functional layer, and a top electrode layer arranged sequentially from bottom to top;

[0007] The dielectric insulating layer is an Al2O3 layer (i.e., the dielectric insulating layer is an Al2O3 dielectric insulating layer).

[0008] The photoferroelectric functional layer is a hexagonal LuMnO3 single crystal layer.

[0009] This invention utilizes the high dielectric constant Al2O3 dielectric insulating layer to form a mirror shield for external free charges, weakening the compensation of interface induced charges for residual polarization, thereby regulating the ferroelectric depolarization field and thus regulating the photovoltaic effect; at the same time, the dielectric insulating layer can effectively block carrier injection, suppress leakage current, reduce dark current, and thus increase the photoelectric response of the device.

[0010] Furthermore, both the bottom electrode layer and the top electrode layer are Pt layers.

[0011] Hexagonal LuMnO3 single crystal was selected as the optoferroelectric material because of its narrow band gap (E). g The Pt electrode has a dielectric constant of approximately 1.5 eV and can be completely absorbed in the visible light range; it has good contact with the LMO electrode; and the Al2O3 dielectric insulating layer has a high dielectric constant (relative dielectric constant of 8-10). These three elements work synergistically to produce high-performance ferroelectric photovoltaic devices.

[0012] Furthermore, the thickness of the bottom electrode layer is 7-100 nm, and the thickness of the top electrode layer is 5-10 nm.

[0013] Preferably, the thicknesses of the bottom electrode layer and the top electrode layer are not the same.

[0014] Setting asymmetric electrodes can create asymmetric charge compensation, thereby maximizing the retention of the depolarization field to promote the separation of photogenerated carriers and thus increase the photoelectric response of the device. The photoresponsivity of Pt / LuMnO3 / Pt ferroelectric photovoltaic devices using asymmetric Pt electrodes (7 nm, 20 nm) is effectively improved by about 10 times compared with those using symmetric Pt electrodes (7 nm, 7 nm).

[0015] Furthermore, the thickness of the dielectric insulating layer is 1.4-11.2 nm, preferably 5.6 nm.

[0016] Furthermore, the thickness of the optoferroelectric functional layer is 50-200 μm.

[0017] Optionally, the substrate includes a silicon (Si) substrate.

[0018] The second technical solution of the present invention: a method for preparing the above-mentioned ferroelectric photovoltaic device based on the shielding effect regulated by a dielectric insulating layer, comprising the following steps:

[0019] Hexagonal LuMnO3 single crystals were grown using a flux method; a dielectric insulating layer was grown on one side of the hexagonal LuMnO3 single crystal using thermal atomic layer deposition (ALD); a bottom electrode layer was grown on the surface of the dielectric insulating layer by magnetron sputtering; a top electrode layer was grown on the other side of the hexagonal LuMnO3 single crystal by magnetron sputtering and using a perforated mask; and the bottom electrode layer of the sample obtained after growing the top electrode layer was fixed to the substrate using silver paste, thus obtaining the ferroelectric photovoltaic device based on the shielding effect regulated by the dielectric insulating layer.

[0020] Further, the growth of hexagonal LuMnO3 single crystals by flux method includes: mixing Lu2O3, MnO and flux, grinding to obtain a mixed powder; sealing the mixed powder and placing it in a heating furnace, heating it to 1200-1300 ℃ at a rate of 3-5 ℃ / min, and holding it at that temperature for 1.5-2.5 h; then cooling it to 1020 ℃ at a rate of 1-1.5 ℃ / h; then cooling it to 1000 ℃ at a rate of 0.2-0.5 ℃ / h; and then turning off the furnace and cooling it (to room temperature) to obtain the hexagonal LuMnO3 single crystal.

[0021] Furthermore, the flux is a mixture of PbO, PbF2 and B2O3.

[0022] Furthermore, the mass ratio of PbO, PbF2, and B2O3 is 6:3:1.

[0023] Furthermore, the molar ratio of Lu2O3 to MnO is 1:2.

[0024] Furthermore, based on the molar ratio, (0.5Lu2O3+MnO):(PbO+PbF2+B2O3) = 1:6.

[0025] Furthermore, the parameters for the thermal atomic layer deposition include: trimethylaluminum and water as precursors; a chamber pressure of 0.2 Torr; a single cycle consisting of a TMA pulse of 0.03-0.1 s, an N2 purge of 15-30 s, a water pulse of 0.02-0.1 s, and an N2 purge of 15-30 s; a growth temperature of 200-300 ℃; and a growth rate of 0.8-1.2 Å / cycle.

[0026] Furthermore, the parameters of the magnetron sputtering include: DC mode, constant power of 10-20 W, working gas of Ar, and growth rate of 0.71-1.42 Å / s.

[0027] Furthermore, the parameters for the magnetron sputtering also include: the growth temperature is room temperature.

[0028] The third technical solution of the present invention: a method for enhancing the photovoltaic effect of photoferroelectrics by regulating the shielding effect using a dielectric insulating layer, wherein a dielectric insulating layer is inserted at the contact interface between the metal electrode and the photoferroelectric.

[0029] The dielectric insulating layer is an Al2O3 layer.

[0030] By inserting a dielectric insulating layer at the contact interface between the metal electrode and the optoferroelectric, the shielding effect of the dielectric insulating layer is modulated to affect the internal electric field of the optoferroelectric to restore its intrinsic depolarization field, thereby enhancing its photoelectric response.

[0031] The present invention discloses the following technical effects:

[0032] This invention actively modulates the shielding level and electric field distribution by inserting a dielectric insulating layer (specifically an Al2O3 dielectric insulating layer) at the interface between the metal electrode and the photoferroelectric material. By changing the boundary conditions, the electric field lines are redistributed, thus achieving shielding of the shielding electric field. This overcomes the limitations of the traditional "polarization-shielding" balance on photoelectric performance, restores the intrinsic depolarization field of the photoferroelectric material, and provides a new approach for constructing highly sensitive and highly responsive ferroelectric photovoltaic devices.

[0033] This invention utilizes the charge-shielding properties of the Al2O3 dielectric insulating layer. By controlling the distribution of free induced charges through the Al2O3 dielectric insulating layer between the hexagonal LuMnO3 single crystal and the Pt electrode, the depolarization field can be modulated, thereby suppressing interfacial recombination of photogenerated electron-hole pairs and promoting the separation of photogenerated carriers. The resulting Pt / Al2O3 / LuMnO3 / Pt ferroelectric photovoltaic device exhibits approximately 70 times higher photoresponsivity compared to the standard Pt / LuMnO3 / Pt ferroelectric photovoltaic device, and reduces dark current by about an order of magnitude.

[0034] The narrow-bandgap hexagonal LuMnO3 single crystal selected in this invention has good ferroelectric properties and light absorption. By suppressing the depolarization field through the Al2O3 dielectric insulating layer, the depolarization field is effectively preserved to drive the separation and migration of photogenerated carriers.

[0035] This invention effectively reduces the recombination probability of photogenerated electron-hole pairs by constructing a simple Pt / Al2O3 / LuMnO3 / Pt ferroelectric photovoltaic device, significantly improving charge separation efficiency and photovoltaic response while reducing dark current. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 The diagrams show the structures of the ferroelectric photovoltaic device without a dielectric insulating layer prepared in Comparative Example 1 and the ferroelectric photovoltaic device with a dielectric insulating layer prepared in Example 1, wherein (a) is the ferroelectric photovoltaic device without a dielectric insulating layer and (b) is the ferroelectric photovoltaic device with a dielectric insulating layer.

[0038] Figure 2 The diagrams show the charge distribution and depolarization field of the ferroelectric photovoltaic device prepared in Comparative Example 1 and the ferroelectric photovoltaic device prepared in Example 1. (a) is a schematic diagram of the charge distribution and depolarization field of the symmetrical ferroelectric photovoltaic device without an Al2O3 dielectric insulating layer prepared in Comparative Example 1; (b) is a schematic diagram of the charge distribution and depolarization field of the symmetrical ferroelectric photovoltaic device with an Al2O3 dielectric insulating layer prepared in Example 1; and (c) is a schematic diagram of the charge distribution and depolarization field of the asymmetric ferroelectric photovoltaic device without an Al2O3 dielectric insulating layer prepared in Comparative Example 1.

[0039] Figure 3 The figures show representative current-voltage dependence (IV curves) measured under dark and light conditions for the ferroelectric photovoltaic device prepared in Comparative Example 1 and the ferroelectric photovoltaic device prepared in Example 1. (a) is a symmetric ferroelectric photovoltaic device without an Al2O3 dielectric insulating layer with a bottom electrode thickness of 7 nm prepared in Comparative Example 1, and (b) is a ferroelectric photovoltaic device with an Al2O3 dielectric insulating layer thickness of 5.6 nm prepared in Example 1.

[0040] Figure 4 A series of Pt / LuMnO3 / Pt with different bottom electrode thicknesses and different Al2O3 dielectric insulating layer thicknesses (t) were prepared for Comparative Example 1 and Example 1. IL The photovoltaic characteristics of the Pt / Al2O3 / LuMnO3 / Pt ferroelectric photovoltaic device vary with the thickness of the Al2O3 dielectric insulating layer, where (a), (c), and (d) represent different prepolarization directions (V0, V ... W > 0, V W < 0) measured short-circuit current (I SC ), open circuit voltage (V) OC ) and maximum optical power (P m (b) shows the short-circuit current difference (ΔI) obtained by positive and negative pre-polarization, as the thickness of the Al2O3 dielectric insulating layer changes. SC The variation with the thickness of the Al2O3 dielectric insulating layer.

[0041] Figure 5The photo-dark switching ratio, rectification ratio, and conductivity characteristics of a series of Pt / LuMnO3 / Pt ferroelectric photovoltaic devices with different bottom electrode thicknesses and different Al2O3 dielectric insulating layer thicknesses prepared in Comparative Example 1 and Example 1 vary with the Al2O3 dielectric insulating layer thickness. (a), (b), (c), and (d) represent the ratio of photocurrent to dark current measured at +10 V (photo-dark switching ratio, Ig). 光 / I 暗 The ratio of the dark current measured at -10 V to the dark current measured at +10 V (rectification ratio, I) -10V / I +10V Different prepolarization directions measured at +1 V voltage (V W >0, V W Photoconductivity (<0) under photoconductivity (<0) 光 ) and dark conductance (X) 暗 ), light-dark conductivity ratio (p) 光 -𝜎 暗 ) / 𝜎 暗 With the change in the thickness of the Al2O3 dielectric insulating layer. Detailed Implementation

[0042] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0043] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0044] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0045] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0046] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0047] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0048] In the following embodiments, comparative examples and test examples of the present invention, if room temperature is involved, it specifically refers to 20~30 ℃.

[0049] All raw materials used in the following embodiments, comparative examples and test examples of this invention are commercially available products, wherein the purity of Lu2O3 is 99.99% and the purity of MnO is 99.5%.

[0050] Example 1

[0051] A ferroelectric photovoltaic device (Pt / Al2O3 / LuMnO3 / Pt) based on the shielding effect regulated by the dielectric insulating layer is shown in the schematic diagram below. Figure 1 As shown in (b), the structure includes a substrate (Si) and a bottom electrode layer (Pt) arranged sequentially from bottom to top. B ), dielectric insulating layer (IL, Al2O3), ferroelectric functional layer (LMO), top electrode layer (Pt) T This ferroelectric photovoltaic device is a symmetrical ferroelectric photovoltaic device (i.e., the bottom electrode layer and the top electrode layer have the same thickness).

[0052] The fabrication steps of the above-mentioned ferroelectric photovoltaic devices are as follows:

[0053] (1) Preparation of hexagonal LuMnO3 single crystals for photoferroelectricity: A mixture of PbO, PbF2 and B2O3 (mass ratio 6:3:1) was used as a flux; Lu2O3 powder, MnO powder and flux powder were mixed (molar ratio, Lu2O3:MnO=1:2, (0.5Lu2O3+MnO):(PbO+PbF2+B2O3)=1:6), and ground with agate for 30 min. The uniformly mixed powder was loaded into a Pt crucible and sealed with argon arc welding to prevent PbO from volatilizing at high temperature. The sealed Pt crucible was placed in a heating furnace and heated to 1280 ℃ at a rate of 4 ℃ / min and held for 2 h; then cooled slowly to 1020 ℃ at a rate of 1 ℃ / h; then cooled to 1000 ℃ at a rate of 0.5 ℃ / h; then the furnace was turned off and cooled to room temperature. The sample was removed and immersed in a 10 vol% HNO3 solution at room temperature for 12 h to dissolve any reagent residues on the surface, ultimately yielding black, shiny hexagonal LuMnO3 flakes, which are the optoferroelectric hexagonal LuMnO3 single crystals (abbreviated as hexagonal LMO single crystals). These single crystals are hexagonal in shape, 100 μm thick, with a surface area of ​​approximately 0.5 mm². 2 Its hexagonal crystal system has a c-axis perpendicular to the maximum surface of the sample.

[0054] (2) ALD growth of Al2O3 dielectric insulating layer

[0055] The hexagonal LMO single crystal surface was cleaned again with a 6.5 vol% HNO3 solution. Then, Al2O3 dielectric insulating layers (ILs) of varying thicknesses (1.4, 2.8, 5.6, and 11.2 nm) were grown on one side of the hexagonal LMO crystal using ALD to obtain multiple samples with different IL thicknesses. The surface on which the Al2O3 dielectric insulating layer was grown was named the bottom surface, and the other surface was named the top surface. ALD parameters included: trimethylaluminum (TMA) and deionized water (H2O) as precursors; chamber pressure of 0.2 Torr; a single cycle consisting of a 0.03 s TMA (30 sccm) pulse, a 25 s N2 (200 sccm) purge, a 0.02 s H2O (30 sccm) pulse, and a 30 s N2 (200 sccm) purge; a growth temperature of 300 ℃ (lowest defect rate and lowest leakage current); and a growth rate of 1 Å / cycle. The growth thickness is controlled by controlling the number of cycles.

[0056] (3) Magnetron sputtering growth of the bottom electrode layer

[0057] Pt was selected as the bottom electrode, and a 7 nm thick continuous bottom electrode was grown on the Al2O3-containing bottom surface of a hexagonal LMO single crystal (i.e., on the surface of the Al2O3 dielectric insulating layer) by magnetron sputtering. The magnetron sputtering parameters included: DC mode, constant power of 10 W, working gas of Ar (0.5 Pa), Pt growth at room temperature, and a growth rate of 0.71 Å / s. A fine-grained Pt bottom electrode layer with low roughness (RMS≈0.3 nm) was obtained.

[0058] (4) Magnetron sputtering growth of the top electrode layer

[0059] Pt was selected as the top electrode. A 7 nm thick square array of top electrodes (each square electrode is 60 μm × 60 μm in size, with an electrode spacing of 20 μm) was grown on the Al₂O₃-free top surface of a hexagonal LMO single crystal (i.e., directly on the surface of the hexagonal LMO single crystal) by magnetron sputtering using a G2300C mask. The magnetron sputtering parameters included: DC mode, constant power of 10 W, working gas of Ar (0.5 Pa), Pt growth at room temperature, and a growth rate of 0.71 Å / s. A fine-grained Pt top electrode layer with low roughness (RMS≈0.3 nm) was obtained.

[0060] (5) Preparation and bonding of the substrate

[0061] A purchased single-sided polished Si wafer was selected as the substrate. The Si wafer was sequentially immersed in acetone, isopropanol, and deionized water for ultrasonic cleaning for 15 minutes each to remove surface contaminants, and then dried with nitrogen. Using silver paste as a binder, silver paste was coated on the polished side of the Si wafer. Then, the bottom electrode layer end of the sample obtained after growing the top electrode layer was adhered to the surface of the Si wafer, and left to stand for 5 minutes to allow the silver paste to dry and set.

[0062] Comparative Example 1

[0063] A schematic diagram of a ferroelectric photovoltaic device (Pt / LuMnO3 / Pt) is shown below. Figure 1 As shown in (a), the structure includes a substrate (Si) and a bottom electrode layer (Pt) arranged sequentially from bottom to top. B ), photoferroelectric functional layer (LMO), top electrode layer (Pt) T ).

[0064] The fabrication steps of the above-mentioned ferroelectric photovoltaic devices are as follows:

[0065] (1) Preparation of hexagonal LuMnO3 single crystals for photoferroelectricity: A mixture of PbO, PbF2 and B2O3 (mass ratio 6:3:1) was used as a flux; Lu2O3 powder, MnO powder and flux powder were mixed (molar ratio, Lu2O3:MnO=1:2, (0.5Lu2O3+MnO):(PbO+PbF2+B2O3)=1:6), and ground with agate for 30 min. The uniformly mixed powder was loaded into a Pt crucible and sealed with argon arc welding to prevent PbO from volatilizing at high temperature. The sealed Pt crucible was placed in a heating furnace and heated to 1280 ℃ at a rate of 4 ℃ / min and held for 2 h; then cooled slowly to 1020 ℃ at a rate of 1 ℃ / h; then cooled to 1000 ℃ at a rate of 0.5 ℃ / h; then the furnace was turned off and cooled to room temperature. The sample was removed and immersed in a 10 vol% HNO3 solution at room temperature for 12 h to dissolve any reagent residues on the surface, ultimately yielding black, shiny hexagonal LuMnO3 flakes, which are the optoferroelectric hexagonal LuMnO3 single crystals (abbreviated as hexagonal LMO single crystals). These single crystals are hexagonal in shape, 100 μm thick, with a surface area of ​​approximately 0.5 mm². 2 Its hexagonal crystal system has a c-axis perpendicular to the maximum surface of the sample.

[0066] (2) Magnetron sputtering growth of the bottom electrode layer

[0067] The hexagonal LMO single crystal surface was cleaned again with a 6.5 vol% HNO3 solution. Then, Pt was selected as the bottom electrode, and a continuous bottom electrode layer of 7 nm or 20 nm thickness was grown on one side of the hexagonal LMO single crystal by magnetron sputtering. The magnetron sputtering parameters included: DC mode, constant power of 10 W, working gas of Ar (0.5 Pa), Pt growth at room temperature, and a growth rate of 0.71 Å / s. A fine-grained Pt bottom electrode layer with low roughness (RMS≈0.3 nm) was obtained. When the bottom electrode thickness was 7 nm, a symmetric ferroelectric photovoltaic device was finally obtained (i.e., the bottom and top electrode layers had the same thickness); when the bottom electrode thickness was 20 nm, an asymmetric ferroelectric photovoltaic device was finally obtained (i.e., the bottom and top electrode layers had different thicknesses).

[0068] (3) Magnetron sputtering growth of the top electrode layer

[0069] Pt was selected as the top electrode. A 7 nm thick square array of top electrodes (each square is 60 μm × 60 μm in size, with an electrode spacing of 20 μm) was grown on the other side of a hexagonal LMO single crystal by magnetron sputtering using a G2300C mask. The magnetron sputtering parameters included: DC mode, constant power of 10 W, working gas Ar (0.5 Pa), Pt growth at room temperature, and a growth rate of 0.71 Å / s. A fine-grained Pt top electrode layer with low roughness (RMS≈0.3 nm) was obtained.

[0070] (4) Preparation of the substrate

[0071] A purchased single-sided polished Si wafer was selected as the substrate. The Si wafer was sequentially immersed in acetone, isopropanol, and deionized water for ultrasonic cleaning for 15 minutes each to remove surface contaminants, and then dried with nitrogen. Using silver paste as a binder, silver paste was coated on the polished side of the Si wafer. Then, the bottom electrode layer end of the sample obtained after growing the top electrode layer was adhered to the surface of the Si wafer, and left to stand for 5 minutes to allow the silver paste to dry and set.

[0072] Test Example 1

[0073] Figure 2 Schematic diagrams of charge distribution and depolarization field of the ferroelectric photovoltaic device prepared in Comparative Example 1 and Example 1, wherein (a) is a schematic diagram of charge distribution and depolarization field of the symmetrical ferroelectric photovoltaic device without Al2O3 dielectric insulating layer prepared in Comparative Example 1, (b) is a schematic diagram of charge distribution and depolarization field of the symmetrical ferroelectric photovoltaic device with Al2O3 dielectric insulating layer prepared in Example 1, and (c) is a schematic diagram of charge distribution and depolarization field of the asymmetric ferroelectric photovoltaic device without Al2O3 dielectric insulating layer prepared in Comparative Example 1. Figure 2 As shown, ferroelectric remanent polarization (P r ) will accumulate bound charges (ρ) on both surfaces of the photoferroelectric material. r These charges are generated inside the crystal in relation to P. r Depolarization fields in opposite directions (E) d This allows photogenerated carriers to migrate towards and be captured by the electrode. However, in reality, free charges (ρ) exist on the surface of the photoferroelectric material or at the interface of the metal electrode. free ) for surface bound charge ρ r Generate compensation (ρ) free +ρ r The value tends towards (→) 0), thus weakening E. d If a high-dielectric insulating layer (IL) is introduced, the shielding compensation charge decreases and the net charge increases (ρ). free +ρ r (≠0), which can effectively retain part of E dUsed for ferroelectric photovoltaic regulation. If asymmetrical bottom and top electrodes are used (e.g., electrodes of different materials and thicknesses), the corresponding charge compensation may be asymmetrical, thus increasing the net charge (ρ). free +ρ r (≠0), it may also increase E d .

[0074] Figure 3 The ferroelectric photovoltaic device prepared in Comparative Example 1 and the ferroelectric photovoltaic device prepared in Example 1 were subjected to illumination (using a 405 nm linearly polarized laser with a laser power of 20 W / cm²). 2 The figure shows the representative current-voltage dependence (IV curve) measured under dark conditions. (a) is a symmetric ferroelectric photovoltaic device without an Al2O3 dielectric insulating layer and with a bottom electrode thickness of 7 nm prepared in Comparative Example 1; (b) is a ferroelectric photovoltaic device with an Al2O3 dielectric insulating layer thickness of 5.6 nm prepared in Example 1. The V curves in the figure are shown in the figure. W The write voltage, i.e., the pre-polarization voltage, V W >0 and V W <0 indicates different positive and negative prepolarization directions; I SC For photogenerated short-circuit current, I SC + Corresponding to prepolarization V W The short-circuit current I measured when >0 SC - Corresponding to prepolarization V W The short-circuit current measured when <0. Comparing (a) and (b), it can be found that the introduction of a 5.6 nm thick Al2O3 dielectric insulating layer significantly improves the short-circuit current (I0) of the device. SC (increased by approximately 70 times) and photogenerated open-circuit voltage (V OC This represents an improvement of approximately 1.5 times, and also increases the short-circuit current difference (ΔI) obtained from positive and negative pre-polarization. SC ΔI SC =I SC - -I SC + This indicates that the introduction of the Al2O3 dielectric insulating layer effectively improves the shielding of free charges against the depolarization field, thereby retaining some of the E. d This enhances the photovoltaic response of ferroelectric photovoltaic devices and the ability of ferroelectric polarization to control the magnitude of the light response (i.e., the photovoltaic effect that changes with the reversal of ferroelectric polarization).

[0075] Figure 4The photovoltaic characteristics of a series of Pt / LuMnO3 / Pt ferroelectric photovoltaic devices with different bottom electrode thicknesses (7 nm, 20 nm) and different Al2O3 dielectric insulating layer thicknesses (0, 1.4, 2.8, 5.6, 11.2 nm) prepared for Comparative Example 1 and Example 1 are shown to vary with the Al2O3 dielectric insulating layer thickness (from the corresponding similar...). Figure 3 (Extracted from the IV curve), where (a), (c), and (d) represent different prepolarization directions (V). W >0, V W <0) measured short-circuit current (I SC ), open circuit voltage (V) OC ) and maximum optical power (P m (b) shows the short-circuit current difference (ΔI) obtained by positive and negative pre-polarization, as the thickness of the Al2O3 dielectric insulating layer changes. SC The change in light response with the thickness of the Al2O3 dielectric insulating layer is shown. Each data point is from measurements of three different devices (top electrodes) in the same sample. Green symbols correspond to the average light response measured for the asymmetric electrode device Pt(20 nm) / LuMnO3 / Pt(7 nm), and blue symbols correspond to the average light response measured for the symmetric electrode devices Pt(7 nm) / LuMnO3 / Pt(7 nm) and Pt(7 nm) / Al2O3 / LuMnO3 / Pt(7 nm). Error bars represent the variance of the measured values. As shown in the figure, even without the introduction of an Al2O3 dielectric insulating layer (IL thickness = 0 nm), the device with the asymmetric electrode (Pt...)... B = 20 nm, Pt T Photovoltaic characteristics (I = 7 nm) SC V OC P m ΔI SC Compared to devices with symmetrical electrodes (Pt) B = Pt T = 7 nm) enhancement; after introducing the Al2O3 dielectric insulating layer, the photovoltaic response initially increases with the increase of the Al2O3 dielectric insulating layer thickness, reaches an extreme value, and then decreases with further increases of the Al2O3 dielectric insulating layer thickness. This indicates that the introduction of the surface asymmetric electrode and the Al2O3 dielectric insulating layer can retain the depolarization field to varying degrees, thereby enhancing the photoelectric response. Simultaneously, after reaching the extreme value, as the thickness of the Al2O3 dielectric insulating layer further increases, the electrode and the photoferroelectric are insulated and separated; at this point, even if E d The presence of this component means that photogenerated charge carriers cannot effectively penetrate the Al2O3 dielectric insulating layer to reach the electrode and form a circuit, thus reducing the photoelectric response.

[0076] Figure 5The light-dark switching ratio, rectification ratio, and conductivity characteristics of a series of Pt / LuMnO3 / Pt ferroelectric photovoltaic devices with different bottom electrode thicknesses (7 nm, 20 nm) and different Al2O3 dielectric insulating layer thicknesses (0, 1.4, 2.8, 5.6, 11.2 nm) prepared for Comparative Example 1 and Example 1 are shown to vary with the Al2O3 dielectric insulating layer thickness as a function of the on / off ratio, rectification ratio, and conductivity characteristics. (From the corresponding similar...) Figure 3 (Extracted from the IV curve), where (a), (b), (c), and (d) are the photocurrents (I) measured at +10 V voltage, respectively. 光 ) and dark current (I 暗 The ratio of light to dark switching ratio (I) 光 / I 暗 Dark current (I) measured at -10 V voltage -10V ) and dark current (I) measured at +10 V voltage +10V The ratio of 1 to 1 (rectification ratio, I) -10V / I +10V Different prepolarization directions measured at +1 V voltage (V W >0, V W Photoconductivity (<0) under photoconductivity (<0) 光 ) and dark conductance (X) 暗 ), light-dark conductivity ratio (p) 光 -𝜎 暗 ) / 𝜎 暗 The graph shows the variation with the thickness of the Al2O3 dielectric insulating layer. Green / yellow symbols correspond to the measured values ​​of Pt(20 nm) / LuMnO3 / Pt(7 nm) for the asymmetric electrode device, while red / blue / black symbols correspond to the measured values ​​of Pt(7 nm) / LuMnO3 / Pt(7 nm) and Pt(7 nm) / Al2O3 / LuMnO3 / Pt(7 nm) for the symmetric electrode devices. As can be seen from the figure, without the introduction of an Al2O3 dielectric insulating layer (IL thickness = 0 nm), the asymmetric electrode device (Pt... B =20 nm, Pt T I = 7 nm) 光 / I 暗 I -10V / I +10V , 𝜎 光 and (S) 光 -𝜎 暗 ) / 𝜎 暗 Compared to symmetrical electrode devices (Pt) B = Pt TThe photoelectric current (IL = 7 nm) increases, but the dark conductivity of the asymmetric electrode device decreases to some extent compared to the symmetric electrode device. After introducing the Al2O3 dielectric insulating layer, the photoelectric current ratio, rectification ratio, photoconductivity (and the difference in conductivity between different pre-polarization directions), and conductivity ratio (and the difference in conductivity ratio between different pre-polarization directions) all initially increase with increasing Al2O3 dielectric insulating layer thickness, reaching a peak at approximately IL thickness = 5.6 nm, and then decreasing with further increases in Al2O3 dielectric insulating layer thickness; however, the dark conductivity generally decreases with increasing Al2O3 dielectric insulating layer thickness. This indicates that the introduction of the asymmetric electrode and the Al2O3 dielectric insulating layer not only modulates the photovoltaic characteristics of the ferroelectric device and reduces the dark current, but also affects the photoelectric current ratio, conductivity, and other values ​​of the device. In fact, typically... 光 >S 暗 Furthermore, the photocurrent is generally proportional to the conductivity of the device, the internal electric field of the device, and the applied external electric field. The improvement of the light-dark ratio and conductivity is itself a manifestation of the improvement of photovoltaic responsivity.

[0077] In summary, by selecting suitable electrodes and introducing dielectric insulating layers to construct ferroelectric photovoltaic devices with different structures, the photoelectric response performance of the devices can be greatly improved.

[0078] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A ferroelectric photovoltaic device based on the shielding effect modulated by a dielectric insulating layer, characterized in that, It includes, from bottom to top, a substrate, a bottom electrode layer, a dielectric insulating layer, an opto-ferroelectric functional layer, and a top electrode layer; The dielectric insulating layer is an Al2O3 layer; The photoferroelectric functional layer is a hexagonal LuMnO3 single crystal layer.

2. The ferroelectric photovoltaic device based on the shielding effect regulated by the dielectric insulating layer as described in claim 1, characterized in that, Both the bottom electrode layer and the top electrode layer are Pt layers.

3. The ferroelectric photovoltaic device based on the shielding effect regulated by the dielectric insulating layer as described in claim 1, characterized in that, The thickness of the bottom electrode layer is 7-100 nm, and the thickness of the top electrode layer is 5-10 nm.

4. The ferroelectric photovoltaic device based on the shielding effect regulated by the dielectric insulating layer as described in claim 1, characterized in that, The thickness of the dielectric insulating layer is 1.4-11.2 nm.

5. The ferroelectric photovoltaic device based on the dielectric insulating layer-controlled shielding effect as described in claim 1, characterized in that, The thickness of the optoferroelectric functional layer is 50-200 μm.

6. A method for fabricating a ferroelectric photovoltaic device based on the shielding effect regulated by a dielectric insulating layer as described in any one of claims 1-5, characterized in that, Includes the following steps: Hexagonal LuMnO3 single crystals were grown using a flux method; a dielectric insulating layer was grown on one side of the hexagonal LuMnO3 single crystal using thermal atomic layer deposition; a bottom electrode layer was grown on the surface of the dielectric insulating layer by magnetron sputtering; a top electrode layer was grown on the other side of the hexagonal LuMnO3 single crystal by magnetron sputtering and using a perforated mask; and the bottom electrode layer of the sample obtained after growing the top electrode layer was fixed to the substrate using silver paste, thus obtaining the ferroelectric photovoltaic device based on the shielding effect regulated by the dielectric insulating layer.

7. The method for fabricating a ferroelectric photovoltaic device based on the shielding effect regulated by a dielectric insulating layer as described in claim 6, characterized in that, The method for growing hexagonal LuMnO3 single crystals via flux includes: mixing Lu2O3, MnO, and flux, grinding them to obtain a mixed powder; sealing the mixed powder and placing it in a heating furnace, heating it to 1200-1300℃ at a rate of 3-5℃ / min, and holding it at that temperature for 1.5-2.5 h; then cooling it to 1020℃ at a rate of 1-1.5℃ / h; then cooling it to 1000℃ at a rate of 0.2-0.5℃ / h; and finally turning off the furnace and cooling it to obtain the hexagonal LuMnO3 single crystal.

8. The method for fabricating a ferroelectric photovoltaic device based on the shielding effect regulated by a dielectric insulating layer as described in claim 6, characterized in that, The parameters for the thermal atomic layer deposition include: trimethylaluminum and water as precursors; chamber pressure of 0.2 Torr; single cycle consisting of a TMA pulse of 0.03-0.1 s, N2 purging of 15-30 s, a water pulse of 0.02-0.1 s, and N2 purging of 15-30 s; growth temperature of 200-300 ℃; and growth rate of 0.8-1.2 Å / cycle.

9. The method for fabricating a ferroelectric photovoltaic device based on the shielding effect regulated by a dielectric insulating layer as described in claim 6, characterized in that, The parameters of the magnetron sputtering include: DC mode, constant power of 10-20 W, working gas of Ar, and growth rate of 0.71-1.42 Å / s.

10. A method for enhancing the photovoltaic effect of photoferroelectric materials by modulating the shielding effect using a dielectric insulating layer, characterized in that, A dielectric insulating layer is inserted at the contact interface between the metal electrode and the optoferroelectric material; The dielectric insulating layer is an Al2O3 layer.

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