TWI894511B - Perovskite film, method for producing perovskite film and photonic device - Google Patents

Abstract

The present invention relates to a perovskite film, a method for producing the perovskite film and a photonic device. The perovskite film is composed of a three-dimensional perovskite layer and a quasi-two-dimensional perovskite layer, and the two layers have specific perovskite compounds. In the method for producing the perovskite film, a specific molar concentration ratio of lead ions to methyl ammonium ions is used to produce the perovskite film, thereby improving power conversion efficiency and stability of the photonic device containing the perovskite film.

Description

Calcium-titanium thin film, calcium-titanium thin film manufacturing method, and optoelectronic device

The present invention relates to a calcium-titanium thin film, a method for manufacturing the calcium-titanium thin film, and a photoelectric device, and in particular to a calcium-titanium thin film composed of a three-dimensional calcium-titanium layer and a quasi-two-dimensional calcium-titanium layer, a method for manufacturing the calcium-titanium thin film, and a photoelectric device.

Photoelectric devices (such as solar cells and photosensors) often use calcium-titanium layers as components for photoelectric conversion. For example, calcium-titanium solar cells use a three-dimensional calcium-titanium layer as the active layer, while photosensors such as light-emitting diodes utilize a calcium-titanium layer as the light-absorbing layer. Although the calcium-titanium compounds in three-dimensional calcium-titanium layers have high photoelectric conversion efficiency, they are easily degraded by external moisture, resulting in poor stability.

A known improvement involves passivating the three-dimensional calcium-titanium layer (e.g., covering it with an organic layer that serves as a passivation layer) to create a p-i-n junction structure. However, this structure is prone to non-radiative recombination, which shortens the carrier lifetime and makes the solar cell's photocurrent unstable, thereby reducing its photoelectric conversion efficiency.

Another improvement approach involves doping three-dimensional calcite and/or quasi-two-dimensional calcite with three-dimensional calcite. For example, hydrophobic molecules such as long-chain ammonium salts can be added to three-dimensional calcite to reduce crystal defects and smoothen interfaces. However, directly adding long-chain ammonium salts to calcite directly transforms the three-dimensional calcite crystal structure, resulting in the simultaneous coexistence of crystals of multiple dimensions within the same calcite layer. This can easily lead to uneven distribution of the constituent elements, causing lead iodide to form residual grains within the calcite layer, thus affecting its uniformity.

In view of this, there is an urgent need to develop a new calcium-titanium thin film and its manufacturing method to improve the shortcomings of optoelectronic devices containing calcium-titanium thin films.

In view of the above-mentioned problems, one aspect of the present invention is to provide a calcium-titanium thin film. This calcium-titanium thin film is composed of a three-dimensional calcium-titanium layer and a quasi-two-dimensional calcium-titanium layer, both of which contain a specific calcium-titanium compound to enhance the photoelectric conversion efficiency and stability of the resulting calcium-titanium thin film.

Another aspect of the present invention provides a method for producing a calcium-titanium thin film. This method utilizes a specific molar concentration ratio of lead ions to methylammonium ions to produce the aforementioned calcium-titanium thin film.

Another aspect of the present invention is to provide a photoelectric device. This photoelectric device includes the aforementioned calcium-titanium thin film.

According to one aspect of the present invention, a calcium-titanium thin film is provided. The thin film is composed of a three-dimensional calcium-titanium layer and a quasi-two-dimensional calcium-titanium layer. The quasi-two-dimensional calcium-titanium layer is disposed on the three-dimensional calcium-titanium layer. The three-dimensional calcium-titanium layer is configured as an n-type semiconductor, while the quasi-two-dimensional calcium-titanium layer is configured as a p-type semiconductor, forming a pn junction between the three-dimensional calcium-titanium layer and the quasi-two-dimensional calcium-titanium layer. The three-dimensional calcium-titanium layer has a calcium-titanium compound represented by the following formula (1), and the quasi-two-dimensional calcium-titanium layer has a calcium-titanium compound represented by the following formula (2): ABX ₃ (1)

L ₂ A _n-1 B _n X _3n+1 (2) In formulas (1) and (2), A represents an alkylammonium ion having a carbon number of 1 to 2 or a monovalent ion of an alkali metal element, B represents a Group 13 metal ion, a Group 14 metal ion, or a Group 15 metal ion, X represents a halogen ion, L represents an alkylammonium ion having a carbon number of 3 to 4, a benzylammonium ion, a phenethylammonium ion, an alkyldiammonium ion having a carbon number of 1 to 3, or an amino acid group having a carbon number of 4 to 6, and n represents an integer from 2 to 5.

According to one embodiment of the present invention, the thickness of the three-dimensional calcium-titanium layer is 300nm to 800nm, and the thickness of the quasi-two-dimensional calcium-titanium layer is 100nm to 300nm.

According to another embodiment of the present invention, a quasi-two-dimensional calcium-titanium layer consists of a first region and a _second region. The first region contains a calcium-titanium compound ( _2-1 ) represented _{by L2A1B2X7} and a _calcium -titanium compound ( _{2-2) represented by L2A2B3X10 . The second} region contains a calcium-titanium compound ( _2-2 ), a calcium-titanium compound ( _{2-3) represented by L2A3B4X13 ,} and a calcium _- titanium compound ( _{2-4 )} represented by _L2A4B5X16 .

According to another embodiment of the present invention, the XRD spectrum of the calcium-titanium compound (2-2) has a diffraction peak in the (111) crystal direction.

According to another embodiment of the present invention, the first region has a crystal plane parallel to the film surface of the calcium-titanium thin film.

According to another embodiment of the present invention, the crystal plane includes a (020) plane, a (040) plane, a (060) plane and/or a (080) plane.

According to another embodiment of the present invention, the second region has a crystal plane perpendicular to the film surface of the calcium-titanium thin film.

Another aspect of the present invention provides a method for manufacturing a calcium-titanium thin film. In this method, a three-dimensional calcium-titanium precursor solution is prepared, wherein the molar ratio of lead ions to methylammonium ions is 1.1 to 1.2. The three-dimensional calcium-titanium precursor solution is deposited on a substrate to obtain a three-dimensional calcium-titanium layer, wherein the three-dimensional calcium-titanium layer has a thickness of 300 nm to 800 nm. The three-dimensional calcium-titanium layer is subjected to a first annealing treatment at 95°C to 105°C to obtain the three-dimensional calcium-titanium layer. A quasi-two-dimensional calcium-titanium precursor solution is prepared, wherein the molar ratio of lead ions to methylammonium ions is 0.7 to 0.9. The quasi-two-dimensional calcium-titanium precursor solution is deposited on the three-dimensional calcium-titanium layer to obtain a quasi-two-dimensional calcium-titanium layer, wherein the quasi-two-dimensional calcium-titanium layer has a thickness of 100 nm to 300 nm. The quasi-two-dimensional calcium-titanium layer is subjected to a second annealing treatment at 105°C to 115°C to obtain the quasi-two-dimensional calcium-titanium layer.

According to one embodiment of the present invention, the operations for depositing a three-dimensional calcium-titanium precursor solution and the operations for depositing a quasi-two-dimensional calcium-titanium precursor solution are selected from the group consisting of spin coating, doctor blade coating, slot coating, spraying, liquid phase crystallization, liquid phase precipitation, ion layer adsorption, hot solvent injection, and any combination thereof.

Another aspect of the present invention provides a photoelectric device. This photoelectric device includes a first electrode layer, an electron transport layer disposed on the first electrode layer, a calcium-titanium thin film disposed on the electron transport layer, a hole transport layer disposed on the calcium-titanium thin film, and a second electrode layer disposed on the hole transport layer. The calcium-titanium thin film is composed of a three-dimensional calcium-titanium layer and a quasi-two-dimensional calcium-titanium layer, with the three-dimensional calcium-titanium layer disposed between the electron transport layer and the quasi-two-dimensional calcium-titanium layer.

The present invention is applied to a calcium-titanium thin film, a method for manufacturing the calcium-titanium thin film, and a photoelectric device. The calcium-titanium thin film is composed of a three-dimensional calcium-titanium layer and a quasi-two-dimensional calcium-titanium layer, both of which contain a specific calcium-titanium compound. The calcium-titanium thin film manufacturing method utilizes a specific molar concentration ratio of lead ions to methylammonium ions to produce the calcium-titanium thin film, thereby improving the power conversion efficiency and stability of the photoelectric device containing the calcium-titanium thin film.

100: Calcium-titanium film

110: Three-dimensional calcium-titanium deposit

120: Quasi-two-dimensional calcium-titanium deposit

121,122: Area

200: Methods

210, 220, 230, 240, 250, 260: Operation

300: Optoelectronic devices

310: First electrode layer

320:Electron transmission layer

330: Calcium-titanium film

331: Three-dimensional calcium-titanium deposit

332: Quasi-two-dimensional calcium-titanium deposit

340: Hole transport layer

350: Second electrode layer

For a more complete understanding of the embodiments of the present invention and its advantages, please refer to the following description in conjunction with the accompanying drawings. It must be emphasized that the various features are not drawn to scale and are for illustrative purposes only. The relevant drawings are described as follows: Figure 1 is a schematic diagram of a calcium-titanium thin film according to one embodiment of the present invention.

Figure 2 is a flow chart showing a method for manufacturing a calcium-titanium thin film according to one embodiment of the present invention.

Figure 3 is a schematic diagram of an optoelectronic device according to one embodiment of the present invention.

Figure 4 shows the reliability test results of the calcium-titanium solar cell according to Example 1 and Comparative Example 1 of the present invention.

Figure 5 shows the external quantum efficiency test results of the photosensor according to Example 1 of the present invention.

Figure 6 is an XRD pattern of the calcium-titanium thin film according to Example 1 of the present invention.

Figure 7 is an XRD pattern of the calcium-titanium thin film according to Example 1 of the present invention.

Figure 8 is a GIWAXS spectrum of the calcium-titanium thin film according to Example 1 of the present invention.

FIG9 is a graph showing the capacitance versus voltage of a capacitor including the calcium-titanium thin film of Example 1.

FIG. 10 is a graph showing the inverse of the cubic capacitance (1/C ³ ) of the capacitor of the calcium-titanium thin film according to Example 1 versus voltage.

The following details the making and using of embodiments of the present invention. However, it should be understood that the embodiments provide many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are for illustrative purposes only and are not intended to limit the scope of the present invention.

Referring to Figure 1, a calcium-titanium thin film 100 is composed of a three-dimensional calcium-titanium layer 110 and a quasi-two-dimensional calcium-titanium layer 120, with the quasi-two-dimensional calcium-titanium layer 120 disposed on the three-dimensional calcium-titanium layer 110. The three-dimensional calcium-titanium layer 110 acts as an n-type semiconductor, and the quasi-two-dimensional calcium-titanium layer 120 acts as a p-type semiconductor, forming a p-n junction structure between the three-dimensional calcium-titanium layer 110 and the quasi-two-dimensional calcium-titanium layer 120, thereby generating a built-in potential within the calcium-titanium thin film 100. This built-in potential facilitates the migration of electrons and holes to the electron transport layer and hole transport layer, respectively, thereby reducing recombination and improving the photoelectric conversion efficiency of the calcium-titanium thin film 100. Furthermore, if the calcium-titanium thin film 100 includes a three-dimensional calcium-titanium layer 110 doped with two-dimensional calcium-titanium, the aforementioned p-n junction structure becomes difficult to form, resulting in a loss of the built-in potential and a reduction in the photoelectric conversion efficiency of the calcium-titanium thin film 100. In some embodiments, the built-in potential of the p-n junction can be 0.5V to 0.7V.

The three-dimensional calcium-titanium layer 110 has a calcium-titanium compound represented by the following formula (1): ABX ₃ (1). In formula (1), A represents an alkylammonium ion having a carbon number of 1 to 2 or a monovalent ion of an alkaline metal element, B represents a Group 13 metal ion, a Group 14 metal ion, or a Group 15 metal ion, and X represents a halogen ion. For example, A can represent CH ₃ NH ₃ ⁺ , C ₂ H ₅ NH ₃ ⁺ , Na ⁺ , K ⁺ , Rb ⁺ , or Cs ⁺ . B can represent Mn ²⁺ , Cu ²⁺ , Ag ⁺ , Au ⁺ , Zn ²⁺ , In ³⁺ , Tl ³⁺ , Ge ²⁺ , Sn ²⁺ , Pb ²⁺ , Bi ³⁺ , or Sb ³⁺ . X can represent Cl ⁻ , Br ⁻ , or I ⁻ . If the three-dimensional calcium-titanium layer 110 does not contain the calcium-titanium compound shown in formula (1), the photoelectric conversion efficiency of the calcium-titanium thin film 100 is reduced.

In some embodiments, the XRD spectrum of the three-dimensional calcium-titanium layer 110 has a diffraction peak in the (110) crystal direction. When the three-dimensional calcium-titanium layer 110 has this diffraction peak, the crystallinity is high, thereby improving the photoelectric conversion efficiency.

Furthermore, the quasi-two-dimensional calcium-titanium layer 120 has a calcium-titanium compound as shown in the following formula (2): L ₂ A _n-1 B _n X _3n+1 (2), wherein A represents an alkylammonium ion having a carbon number of 1 to 2 or a monovalent ion of an alkali metal element, B represents a Group 13 metal ion, a Group 14 metal ion, or a Group 15 metal ion, X represents a halogen ion, L represents an alkylammonium ion having a carbon number of 3 to 4, a benzylammonium ion, a phenethylammonium ion, an alkyldiammonium ion having a carbon number of 1 to 3, or an amino acid group having a carbon number of 4 to 6, and n represents an integer from 2 to 5. If the quasi-two-dimensional calcium-titanium layer 120 does not have the calcium-titanium compound shown in formula (2), the quasi-two-dimensional calcium-titanium layer 120 cannot protect the three-dimensional calcium-titanium layer 110 from being degraded by external moisture, thereby reducing the stability of the calcium-titanium film 100.

In the three-dimensional calcium-titanium layer 110, methylammonium ions (MA ⁺ ) are preferably present compared to other long carbon chain ammonium ions. They can enhance the hydrogen bonding and Coulomb force interactions between iodine atoms and hydrogen atoms within the calcium-titanium structure of the three-dimensional calcium-titanium layer 110 and the quasi-two-dimensional calcium-titanium layer 120, thereby further stabilizing the structure of the three-dimensional calcium-titanium layer 110 and the quasi-two-dimensional calcium-titanium layer 120, thereby further improving the stability of the calcium-titanium film 100.

In the quasi-two-dimensional calcium-titanium layer 120 , n-butylammonium ions (BA ⁺ ) are more hydrophobic than ethylamine ions and propylamine ions. Therefore, they can better protect the three-dimensional calcium-titanium layer 110 from degradation by external moisture, thereby further improving the stability of the calcium-titanium film 100 .

In some embodiments, the quasi-two-dimensional calcium-titanium layer 120 is composed of a first region 121 and a second region 122, wherein the second region 122 is located between the first region 121 and the three-dimensional calcium-titanium layer 110. When the first region 121 and the second region 122 are arranged in the aforementioned manner, the photoelectric conversion efficiency and stability are further improved.

First region 121 contains a calcium- _titanium compound ( _{2-1) represented by L2A1B2X7 and a calcium} -titanium compound ( _2-2 ) represented _{by L2A2B3X10} . Second region 122 contains a calcium-titanium compound ( _2-2 ) represented _{by L2A2B3X10} , a _calcium - _titanium compound (2-3) represented by _L2A3B4X13 , and a _calcium - _titanium compound ( _{2-4) represented by L2A4B5X16 . When} both first region 121 and second region ₁₂₂ contain the corresponding calcium-titanium compounds, photoelectric conversion efficiency and stability are improved.

Furthermore, the ratio of the calcium-titanium compound (2-2) to the calcium-titanium compound (2-1) in the first region 121 is greater than the ratio of the calcium-titanium compound (2-2) to the sum of the calcium-titanium compound (2-3) and the calcium-titanium compound (2-4) in the second region 122, thereby enhancing the effect of blocking external moisture. Furthermore, the XRD pattern of the calcium-titanium compound (2-2) exhibits a diffraction peak in the (111) crystal direction. When the calcium-titanium compound (2-2) has this diffraction peak, it facilitates the second region 122 to bond the quasi-two-dimensional calcium-titanium layer 120 and the three-dimensional calcium-titanium layer 110, thereby promoting the separation and transmission of electrons and holes in the calcium-titanium thin film 100, thereby improving the photoelectric conversion efficiency.

In a preferred embodiment, the first region 121 has a crystal plane parallel to the film surface of the calcium-titanium thin film 100. The crystal planes include a (020) plane, a (040) plane, a (060) plane, and/or a (080) plane. When the first region 121 has the aforementioned crystal planes, the effect of blocking external moisture and oxygen is enhanced, thereby further improving stability.

In addition, the second region 122 has a crystal plane perpendicular to the film surface of the calcium-titanium thin film 100. The crystal plane includes a (111) plane, which is more conducive to the second region 122 bonding the quasi-two-dimensional calcium-titanium layer 120 and the three-dimensional calcium-titanium layer 110, and helps the first region 121 block external water vapor, thereby improving the photoelectric conversion efficiency and stability.

Continuing with FIG. 2 , in method 200 for fabricating a calcium-titanium thin film, a three-dimensional calcium-titanium precursor solution is prepared, as shown in operation 210 . The molar concentration ratio of lead ions to methylammonium ions in the three-dimensional calcium-titanium precursor solution is 1.0 to 1.4, preferably 1.1 to 1.2, and more preferably 1.2. If the molar ratio of lead ions to methylammonium ions in the three-dimensional calcium-titanium precursor solution is greater than 1.4, the lead ions will precipitate in large quantities as lead halide salts, causing impurities in the subsequently produced three-dimensional calcium-titanium layer and reducing the photoelectric conversion efficiency and stability of the calcium-titanium thin film.

On the contrary, if the above-mentioned molar concentration ratio is less than 1.0, the three-dimensional calcium-titanium layer produced will have holes, which will reduce the photoelectric conversion efficiency and stability of the calcium-titanium film. Furthermore, if the molar concentration ratio is greater than 1.4 or less than 1.0, the three-dimensional calcium-titanium layer does not have the calcium-titanium compound shown in the above formula (1). In a preferred embodiment, the molar concentration ratio is 1.1 to 1.2, and more preferably 1.2, so that the three-dimensional calcium-titanium layer produced from the three-dimensional calcium-titanium precursor solution can be used as an n-type semiconductor.

After operation 210, a three-dimensional calcium-titanium precursor solution is deposited on the substrate to obtain a three-dimensional calcium-titanium layer, as shown in operation 220. The deposition operation 220 can be selected from the group consisting of spin coating, doctor blade coating, slit coating, spray coating, liquid phase crystallization, liquid phase precipitation, ion layer adsorption, hot solvent injection, and any combination thereof. Preferably, compared to spin coating, the doctor blade method can increase the coating area of the three-dimensional calcium-titanium precursor solution and improve its coating uniformity.

Specifically, the doctor blade coating speed can be between 25 mm/s and 35 mm/s, preferably 30 mm/s, to further improve the uniformity of the coating of the three-dimensional calcium-titanium precursor solution and facilitate the formation of three-dimensional and quasi-two-dimensional calcium-titanium layers, thereby improving the photoelectric conversion efficiency and stability of the calcium-titanium thin film.

During coating, the substrate can be heated to provide a heat source. This heat source is used to remove the solvent from the three-dimensional calcium-titanium precursor solution during coating, thereby forming a three-dimensional calcium-titanium layer. The heating temperature can be between 145°C and 155°C, preferably 150°C, to improve photoelectric conversion efficiency.

The thickness of the three-dimensional calcium-titanium layer is 300nm to 800nm, preferably 500nm to 600nm, and more preferably 550nm. If the thickness of the three-dimensional calcium-titanium layer is outside the aforementioned range, the resulting three-dimensional calcium-titanium layer is likely to contain defects.

After operation 220, the three-dimensional calcium-titanium layer is annealed at 95°C to 105°C to obtain the three-dimensional calcium-titanium layer, as shown in operation 230. If the annealing temperature is not within the aforementioned range, the obtained three-dimensional calcium-titanium layer is prone to the presence of impurities and/or defects.

After operation 230, a quasi-two-dimensional calcium-titanium precursor solution is prepared, as shown in operation 240. The molar concentration ratio of lead ions to methylammonium ions in the quasi-two-dimensional calcium-titanium precursor solution is 0.7 to 0.9. If this molar concentration ratio is less than 0.7, the quasi-two-dimensional calcium-titanium layer produced does not have the calcium-titanium compound shown in formula (2) above, and its stability is reduced. In a preferred embodiment, the molar concentration ratio is 0.75 to 0.85, so that the quasi-two-dimensional calcium-titanium layer produced by the quasi-two-dimensional calcium-titanium precursor solution can be used as a p-type semiconductor.

After operation 240, a quasi-two-dimensional calcium-titanium precursor solution is deposited on the three-dimensional calcium-titanium layer to obtain the quasi-two-dimensional calcium-titanium layer, as shown in operation 250. In an embodiment using a coating method, the three-dimensional calcium-titanium layer is first heated to 165°C to 175°C before the quasi-two-dimensional calcium-titanium precursor solution is coated thereon to further improve the photoelectric conversion efficiency and stability.

Preferably, when the heating temperature is 170°C, the first region contains the calcium-titanium compound (2-1) and the calcium-titanium compound (2-2), and the second region contains the calcium-titanium compound (2-2), the calcium-titanium compound (2-3), and the calcium-titanium compound (2-4).

The thickness of the quasi-two-dimensional calcium-titanium layer is 100nm to 300nm, preferably 100nm to 200nm. If this thickness is outside the aforementioned range, the resulting quasi-two-dimensional calcium-titanium layer is susceptible to the presence of impurities and/or defects, thereby reducing stability.

Similar to the three-dimensional calcium-titanium layer described above, the quasi-two-dimensional calcium-titanium layer deposition process 250 can also be selected from the group consisting of spin coating, doctor blade coating, slit coating, spray coating, liquid phase crystallization, liquid phase precipitation, ion layer adsorption, hot solvent injection, and any combination thereof. In some embodiments, the coating rate of the aforementioned coating method can be 35 mm/s to 45 mm/s, preferably 40 mm/s, to facilitate forming the quasi-two-dimensional calcium-titanium layer with a first region and a second region.

For example, in the liquid phase crystallization method, a calcium-titanium precursor solution is prepared with a solvent (such as dimethylformamide (DMF) and dimethyl sulfoxide (DMSO)), then cooled to utilize the temperature difference to supersaturate the calcium-titanium precursor solution, and then calcium-titanium crystals are precipitated, and then annealed at 90°C for 10 minutes. In the liquid phase precipitation method, a calcium-titanium precursor solution is prepared using a solvent with a high solubility for the calcium-titanium precursor (such as DMF and DMSO). Another solvent with a lower solubility for the calcium-titanium precursor (serving as a countersolvent, such as toluene and hexane) is then gradually added dropwise to the calcium-titanium precursor solution. The difference in solubility causes the calcium-titanium crystals to precipitate.

For example, in the ionic layer adsorption method, two solvents are used to prepare a lead iodide solution and an n-butylammonium iodide solution, respectively. The substrate is then immersed in the lead iodide solution and the n-butylammonium iodide solution, removed, baked, and annealed at 90°C to 110°C to obtain a calcium-titanium thin film. In the hot solvent injection method, two solvents are used to prepare a lead iodide solution and an n-butylammonium iodide solution, respectively. The lead iodide solution is then injected into the n-butylammonium iodide solution (or vice versa) to precipitate calcium-titanium crystals. The calcium-titanium crystals are then removed by centrifugation and annealed at 90°C to 200°C.

After operation 250, the quasi-two-dimensional calcite-titanium coating is annealed at 105°C to 115°C to obtain a quasi-two-dimensional calcite-titanium layer, as shown in operation 260. If the annealing temperature is outside the aforementioned range, the resulting quasi-two-dimensional calcite-titanium layer is prone to the presence of impurities and/or defects, thereby reducing stability.

In some preferred embodiments, the annealing time of the three-dimensional calcium-titanium layer and the quasi-two-dimensional calcium-titanium layer can be 12 minutes to 17 minutes, which is conducive to making the XRD spectrum of the three-dimensional calcium-titanium layer have a diffraction peak in the (110) crystal direction. In some specific examples, the first region has a crystal plane parallel to the film surface of the calcium-titanium film, and the second region has a crystal plane perpendicular to the film surface of the calcium-titanium film.

Continuing with FIG. 3 , the optoelectronic device 300 includes a first electrode layer 310 , an electron transport layer 320 disposed on the first electrode layer 310 , a calcium-titanium thin film 330 disposed on the electron transport layer 320 , a hole transport layer 340 disposed on the calcium-titanium thin film 330 , and a second electrode layer 350 disposed on the hole transport layer 340 . The calcium-titanium thin film 330 is composed of a three-dimensional calcium-titanium layer 331 and a quasi-two-dimensional calcium-titanium layer 332. The three-dimensional calcium-titanium layer 331 is disposed between the electron transport layer 320 and the quasi-two-dimensional calcium-titanium layer 332. Each layer is described below.

The materials of the first electrode layer 310 and the second electrode layer 350 may include gold, silver, copper, aluminum, palladium, nickel, or a combination thereof. The material of the electron transport layer 320 may include indium tin oxide, fluoride-doped tin oxide, aluminum zinc oxide, or zinc indium oxide.

Furthermore, the calcium-titanium thin film 330 has been described in detail above and will not be repeated here. Furthermore, the material of the hole transport layer 340 may include poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) and 2,2',7,7'-tetrakis[N,N-bis(4-methoxyphenyl)amino]-9,9'-spirobifluorene (spiro-OMeTAD).

The aforementioned first electrode layer 310, electron transport layer 320, hole transport layer 340, and second electrode layer 350 can all be fabricated using methods commonly used by those skilled in the art, such as vapor deposition, sputtering, thermal evaporation, and electroplating. Furthermore, the thicknesses of these layers can also be within the range commonly used by those skilled in the art.

In some applications, the optoelectronic device 300 may include a calcium-titanium solar cell and a photodetector.

The following examples illustrate the application of the present invention, but are not intended to limit the present invention. Anyone skilled in the art can make various modifications and improvements without departing from the spirit and scope of the present invention.

Preparation of calcium-titanium thin films, calcium-titanium solar cells, and photosensors

Example 1

On a glass substrate with a fluorine-doped tin oxide (FTO) layer, a _TiO2 layer (as an electron transport layer) was evaporated on the FTO layer (as the first electrode layer).

Then, dimethylformamide and dimethylsulfoxide were used to prepare methylammonium iodide solution and lead iodide solution, and isopropyl alcohol was used to prepare n-butylammonium iodide solution. 1.0M methylammonium iodide solution and 1.1M lead iodide solution were mixed to form a three-dimensional calcium-titanium precursor solution. Under atmospheric pressure, a doctor blade was used to apply the three-dimensional calcium-titanium precursor solution with a thickness of 550nm on _{a TiO2} layer preheated to 150°C at a coating rate of 30 mm/s, and then annealed at 100°C for 15 minutes to obtain a three-dimensional calcium-titanium layer having a calcium-titanium compound as shown in formula (1).

Separately, 1.0M methylammonium iodide solution, 0.3M n-butylammonium iodide solution, and 0.8M lead iodide solution were mixed to form a quasi-two-dimensional calcium-titanium precursor solution. Under atmospheric pressure, a doctor blade was used to apply a 200nm thick quasi-two-dimensional calcium-titanium precursor solution onto the aforementioned three-dimensional calcium-titanium layer, which had been preheated to 170°C, at a coating rate of 40 mm/s. The layer was then annealed at 110°C for 15 minutes to obtain a quasi-two-dimensional calcium-titanium layer having the calcium-titanium compound shown in formula (2), thus obtaining the calcium-titanium film of Example 1.

Next, a Spiro-OMeTAD solution was prepared by mixing chlorobenzene, lithium salt, acetonitrile, and an oxidizing agent (Model FK-209). This solution was then spin-coated onto the quasi-two-dimensional calcium-titanium layer cooled to room temperature to form a hole transport layer. A gold layer was then thermally evaporated onto the hole transport layer to serve as the second electrode layer. Following this, the solar cell and photosensor were packaged and connected to external circuits, respectively, to obtain the calcium-titanium solar cell and photosensor of Example 1.

Comparison Examples 1 and 2

The calcium-titanium thin films, calcium-titanium solar cells, and photosensors in Comparative Examples 1 and 2 were prepared using the same method as Example 1. The differences were that Comparative Example 1 did not use a quasi-two-dimensional calcium-titanium layer, while Comparative Example 2 used a two-dimensional calcium-titanium layer as an n-type semiconductor and a quasi-two-dimensional calcium-titanium layer as an n-type semiconductor. In Comparative Example 2, the two-dimensional calcium-titanium layer precursor solution was a mixture of 1.0 M methylammonium iodide, 0.3 M n-butylammonium iodide solution, and 1.1 M lead iodide solution. The specific conditions and evaluation results for Example 1 and Comparative Examples 1-2 are shown in Table 1 below.

Evaluation method

1. Testing of short-circuit current density, open-circuit voltage, fill factor, and conversion efficiency of calcium-titanium solar cells

The calcium-titanium solar cells of Example 1 and Comparative Examples 1-2 were tested for short-circuit current density, open-circuit voltage, fill factor, and power conversion efficiency using methods commonly used by those skilled in the art. Power conversion efficiency is used to evaluate the photoelectric conversion efficiency of the calcium-titanium thin film. The power conversion efficiency was measured over time to track changes in power conversion efficiency. This represents reliability, assessing the stability of the calcium-titanium solar cell and reflecting the stability of the calcium-titanium thin film.

2. Testing of external quantum efficiency, detectivity, and response of photodetectors

The photosensors of Example 1 and Comparative Examples 1 and 2 were tested for external quantum efficiency, detectivity, and responsiveness using methods commonly used by those skilled in the art. Furthermore, the external quantum efficiency of the photosensors was measured over 200 days in an atmospheric environment with a relative humidity of 50% to 80% to evaluate the stability of the photosensors, which also reflects the stability of the calcium-titanium thin film.

3. Measurement of crystal planes and arrangement of three-dimensional and quasi-two-dimensional calcium-titanium layers

Grazing-incidence wide-angle X-ray scattering (GIWAXS) and X-ray diffraction (XRD) patterns were measured on the three-dimensional and quasi-two-dimensional calcium-titanium layers in the calcium-titanium thin films. The crystal planes and arrangement of the three-dimensional and quasi-two-dimensional calcium-titanium layers were analyzed based on the patterns.

Referring to Table 1 and Figure 4, compared to Comparative Examples 1 and 2, Example 1 uses a calcium-titanium thin film with a quasi-two-dimensional calcium-titanium layer as the active layer of a calcium-titanium solar cell, thereby improving power conversion efficiency and stability. Furthermore, the calcium-titanium thin film of Example 1 has both a three-dimensional calcium-titanium layer and a quasi-two-dimensional calcium-titanium layer to form a p-n junction, thereby increasing the short-circuit current density.

Refer to Table 2 and Figure 5. Compared to Comparative Examples 1 and 2, Example 1 uses a calcium-titanium thin film with a quasi-two-dimensional calcium-titanium layer as the light absorption layer of the photosensor, thereby improving the external quantum efficiency, detectivity, response, and stability.

Referring to FIG. 6 , the quasi-two-dimensional calcium-titanium layer of Example 1 is composed of a first region and a second region. The calcium-titanium compound (2-1) has a (040) crystal plane, as indicated by the label "(040) ₂ " in FIG. The calcium-titanium compound (2-2) has a (040) crystal plane, a (060) crystal plane, and a (080) crystal plane, as indicated by the labels "(040) ₃ ", "(060) ₃ ", and "(080) ₃ " in FIG. 6 , respectively.

Please refer to Figure 7. As the incident angle increases, the depth of X-rays penetrating into the calcium-titanium film becomes deeper, and the diffraction peak intensity of the crystal plane (110) of the calcium-titanium compound indicated by ABX ₃ of the three-dimensional calcium-titanium layer gradually increases (as indicated by the label "(110) _3D " in Figure 7). This indicates that the three-dimensional calcium-titanium layer is located in the inner layer of the calcium-titanium film. When the incident angle is 0.5 degrees, the diffraction peaks of the (040) and (080) planes are stronger (as shown by the labels "(040) ₃ " and "(080) ₅ " in Figure 7). This indicates that the first region of the quasi-two-dimensional calcium-titanium layer is located in the outermost layer of the calcium-titanium film. In other words, the second region of the quasi-two-dimensional calcium-titanium layer is located in the middle layer of the calcium-titanium film.

Referring to FIG8 , in the quasi-two-dimensional calcium-titanium layer of Example 1, the calcium-titanium compound (2-1) has a (020) crystal plane and a (040) crystal plane, as indicated by the labels “(020) ₂ ” and “(040) ₂ ” in FIG8 . The calcium-titanium compound (2-2) has a (040) crystal plane, a (060) crystal plane, a (080) crystal plane, and a (111) crystal plane, as indicated by the labels “(040) ₃ ”, “(060) ₃ ”, “(080) ₃ ”, and “(111)” in FIG8 , respectively. Furthermore, the label “FTO” in FIG8 represents the diffraction arc generated by X-rays on the FTO layer. The first region has a crystal plane parallel to the film surface of the calcium-titanium film, and the second region has a crystal plane perpendicular to the film surface of the calcium-titanium film.

Electrodes are placed on both sides of the calcium-titanium thin film of Example 1, and external circuitry is added to form a capacitor. See Figure 9, which plots capacitance versus voltage for a capacitor containing the calcium-titanium thin film of Example 1. Based on this figure, Figure 10 plots the inverse of the cube of capacitance (1/C ³ ) versus voltage. The Y-axis of Figure 10 uses scientific notation, for example, "2.00E+27" represents "2.00×10 ²⁷ ." Then, based on the theory of the Fermi level, a regression line analysis was performed on the range of 0.6V to 1.0V in Figure 10. The built-in potential of the pn junction of the calcium-titanium thin film in Example 1 was calculated to be 0.62V based on the slope of the regression line.

In summary, the present invention provides a calcium-titanium thin film, a method for manufacturing a calcium-titanium thin film, and an optoelectronic device. The calcium-titanium thin film is composed of a three-dimensional calcium-titanium layer and a quasi-two-dimensional calcium-titanium layer, both of which contain a specific calcium-titanium compound. The calcium-titanium thin film manufacturing method utilizes a specific molar concentration ratio of lead ions to methylammonium ions to produce the calcium-titanium thin film, thereby improving the power conversion efficiency and stability of optoelectronic devices containing the calcium-titanium thin film.

Although the present invention has been disclosed above in terms of embodiments, this is not intended to limit the present invention. Anyone with ordinary skill in the art to which the present invention pertains may make various modifications and improvements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the scope of the patent application attached hereto.

100: Calcium-titanium film

110: Three-dimensional calcium-titanium deposit

120: Quasi-two-dimensional calcium-titanium deposit

121,122: Area

Claims (10)

A calcium-titanium thin film is composed of a three-dimensional calcium-titanium layer and a quasi-two-dimensional calcium-titanium layer. The quasi-two-dimensional calcium-titanium layer is disposed on the three-dimensional calcium-titanium layer. The three-dimensional calcium-titanium layer is configured as an n-type semiconductor, and the quasi-two-dimensional calcium-titanium layer is configured as a p-type semiconductor, so as to form a pn junction between the three-dimensional calcium-titanium layer and the quasi-two-dimensional calcium-titanium layer. The three-dimensional calcium-titanium layer has a calcium-titanium compound represented by the following formula (1), and the quasi-two-dimensional calcium-titanium layer has a calcium-titanium compound represented by the following formula (2): ABX ₃ (1) L ₂ A _n-1 B _n X _3n+1 (2) In formula (1) and formula (2), A represents an alkylammonium ion having 1 to 2 carbon atoms or a monovalent ion of an alkali metal element, B represents a Group 13 metal ion, a Group 14 metal ion, or a Group 15 metal ion, X represents a halogen ion, L represents an alkylammonium ion having 3 to 4 carbon atoms, a benzylammonium ion, a phenethylammonium ion, an alkyldiammonium ion having 1 to 3 carbon atoms, or an amino acid group having 4 to 6 carbon atoms, and n represents an integer from 2 to 5. The calcium-titanium thin film as described in claim 1, wherein a thickness of the three-dimensional calcium-titanium layer is 300 nm to 800 nm, and a thickness of the quasi-two-dimensional calcium-titanium layer is 100 nm to 300 nm. The calcium-titanium film of claim 1, wherein the quasi-two-dimensional calcium-titanium layer is composed of a first region and a second region, the second region being located between the first region and the three-dimensional calcium-titanium layer, the first region comprising a calcium-titanium compound (2-1) represented by L ₂ A ₁ B ₂ X ₇ and a calcium-titanium compound (2-2) represented by L ₂ A ₂ B ₃ X ₁₀ , and the second region comprising the calcium-titanium compound (2-2), a calcium-titanium compound (2-3) represented by L ₂ A ₃ B ₄ X ₁₃ , and a calcium-titanium compound (2-4) represented by L ₂ A ₄ B ₅ X ₁₆ . The calcium-titanium film as described in claim 3, wherein an XRD spectrum of the calcium-titanium compound (2-2) has a diffraction peak in the (111) crystal direction. The calcium-titanium thin film as described in claim 3, wherein the first region has a crystal plane parallel to a film surface of the calcium-titanium thin film. The calcium-titanium thin film as described in claim 5, wherein the crystal plane includes a (020) plane, a (040) plane, a (060) plane and/or a (080) plane. The calcium-titanium thin film as described in claim 3, wherein the second region has a crystal plane perpendicular to a film surface of the calcium-titanium thin film. A method for manufacturing a calcium-titanium thin film comprises: preparing a three-dimensional calcium-titanium precursor solution, wherein the molar ratio of lead ions to methylammonium ions is 1.1 to 1.2; depositing the three-dimensional calcium-titanium precursor solution on a substrate to obtain a three-dimensional calcium-titanium coating, wherein the three-dimensional calcium-titanium coating has a thickness of 300 nm to 800 nm; Performing a first annealing treatment on the three-dimensional calcium-titanium coating at 95° C. to 105° C. to obtain a three-dimensional calcium-titanium layer, wherein the three-dimensional calcium-titanium layer has a calcium-titanium compound represented by the following formula (1): ABX ₃ (1); preparing a quasi-two-dimensional calcium-titanium precursor solution, wherein a molar concentration ratio of the lead ions to the methylammonium ions is 0.7 to 0.9; Depositing the quasi-two-dimensional calcium-titanium precursor solution on the three-dimensional calcium-titanium layer to obtain a quasi-two-dimensional calcium-titanium coating, wherein the quasi-two-dimensional calcium-titanium coating has a thickness of 100 nm to 300 nm; and performing a second annealing treatment on the quasi-two-dimensional calcium-titanium coating at 105° C. to obtain a quasi-two-dimensional calcium-titanium layer, wherein the quasi-two-dimensional calcium-titanium layer has a calcium-titanium compound represented by the following formula (2): L ₂ An _{-1 Bn} X _3n+1 (2), In formula (1) and formula (2), A represents an alkylammonium ion having 1 to 2 carbon atoms or a monovalent ion of an alkali metal element, B represents a Group 13 metal ion, a Group 14 metal ion, or a Group 15 metal ion, X represents a halogen ion, L represents an alkylammonium ion having 3 to 4 carbon atoms, a benzylammonium ion, a phenethylammonium ion, an alkyldiammonium ion having 1 to 3 carbon atoms, or an amino acid group having 4 to 6 carbon atoms, and n represents an integer from 2 to 5. The method for manufacturing a calcium-titanium thin film as described in claim 8, wherein the operation of depositing the three-dimensional calcium-titanium precursor solution and the operation of depositing the quasi-two-dimensional calcium-titanium precursor solution are selected from a group consisting of spin coating, doctor blade coating, slit coating, spraying, liquid phase crystallization, liquid phase precipitation, ion layer adsorption, hot solvent injection, and any combination thereof. A photoelectric device comprises: a first electrode layer; an electron transport layer disposed on the first electrode layer; a calcium-titanium thin film as described in any one of claims 1 to 7 disposed on the electron transport layer, wherein the calcium-titanium thin film is composed of a three-dimensional calcium-titanium layer and a quasi-two-dimensional calcium-titanium layer, the three-dimensional calcium-titanium layer being disposed between the electron transport layer and the quasi-two-dimensional calcium-titanium layer; a hole transport layer disposed on the calcium-titanium thin film; and a second electrode layer disposed on the hole transport layer.