KR102112927B1 - Dopant for perovskite material, perovskite material comprising the dopant, and method of forming the same - Google Patents

Abstract

A dopant for a perovskite material, a perovskite material comprising the dopant, and a method of forming the same are provided.
The dopant for the perovskite material is a dopant introduced into the halide perovskite material, and includes one or more of compounds SbX ₃ and BiX ₃ . In the formulas SbX ₃ and BiX ₃ , X includes at least one or more of F, Cl, Br, and I.
The perovskite material includes a halide perovskite compound and a dopant introduced into the halide perovskite compound and comprising one or more of compounds SbX ₃ and BiX ₃ . In the formulas SbX ₃ and BiX ₃ , X includes at least one or more of F, Cl, Br, and I.
The method of forming the perovskite material includes mixing CsX, SnX ₂ , and a dopant to heat the mixture. The dopant includes one or more of compounds SbX ₃ and BiX ₃ , wherein X in the formulas CsX, SnX ₂ , SbX ₃ , and BiX ₃ is at least one or more of F, Cl, Br, and I Includes.

Description

Dopant for a perovskite material, perovskite material containing the dopant and a method for forming the same {DOPANT FOR PEROVSKITE MATERIAL, PEROVSKITE MATERIAL COMPRISING THE DOPANT, AND METHOD OF FORMING THE SAME}

The present invention relates to a dopant for a perovskite material, a perovskite material containing the dopant, and a method for forming the same.

Perovskite (Perovskite) is the name of CaTiO ₃ (Calcium titanium oxide) mineral, which was first discovered in Russia. In general, it has the structure of ABX ₃ , and there are hundreds of types known depending on which atoms are in A, B, and X, and electrical properties vary from conductors to semiconductors and non-conductors.

Among the perovskite materials, CH ₃ NH ₃ PbI ₃ (Methyl ammonium lead iodide), which has recently been spotlighted, shows excellent photoelectric conversion efficiency of over 20% when it is made of solar cells. In addition to solar cells, perovskite has been applied to various fields such as transistors and LEDs due to its excellent electrical properties and the advantage of being capable of liquid phase processing.

Perovskite materials, which show the highest efficiency in solar cells, contain Pb (lead) in their constituent elements, which can cause environmental problems when commercialized. Therefore, finding another element to replace it is one major trend in recent perovskite research, and the most promising candidate as a substitute is Sn (annotation) from the same group 14. Although Sn-based perovskite has not yet reached the efficiency of a material containing lead, it is promising because it shows similar properties to Pb and excellent photoelectric properties, and many studies have been conducted.

As a representative Sn-based perovskite material, CsSnI ₃ has a high current density (30mA / ㎠) and is a substitute for CH ₃ NH ₃ PbI ₃ material containing lead, a toxic component of existing perovskite solar cells. It is counted. CsSnI ₃ has a yellow phase (Y) with a large bandgap of 2.49 eV and a photoelectrically active black phase (B-γ) with a bandgap of 1.3 eV at room temperature and a photoelectrically inactive state. These two phases have a small energy difference, so the black phase easily changes to a yellow phase, and these properties act as an inhibitor to various device applications.

In order to solve the above problems, the present invention provides a dopant that can stabilize the perovskite material.

The present invention provides a perovskite material having excellent stability.

The present invention provides a method of forming the perovskite material.

Other objects of the present invention will become apparent from the following detailed description and accompanying drawings.

The dopant for a perovskite material according to embodiments of the present invention is a dopant introduced into a halide perovskite material, and includes one or two or more of compounds SbX ₃ and BiX ₃ . In the formulas SbX ₃ and BiX ₃ , X includes at least one or more of F, Cl, Br, and I.

The perovskite material according to the embodiments of the present invention includes a halide perovskite compound and a dopant introduced into the halide perovskite compound and comprising one or more of compounds SbX ₃ and BiX ₃ do. In the formulas SbX ₃ and BiX ₃ , X includes at least one or more of F, Cl, Br, and I.

A method of forming a perovskite material according to embodiments of the present invention includes heating by mixing CsX, SnX ₂ , and a dopant. The dopant includes one or more of compounds SbX ₃ and BiX ₃ , wherein X in the formulas CsX, SnX ₂ , SbX ₃ , and BiX ₃ is at least one or more of F, Cl, Br, and I Includes.

The dopant (BiX ₃ , SbX _{3 ,} X = F, Cl, Br, I) according to embodiments of the present invention can stabilize a pure perovskite structure at room temperature with only a small amount added. The P orbits of Bi and Sb contribute to narrowing the band gap of Sn-based perovskite materials. Through the addition of the dopant, the formation energy of the perovskite phase (black phase) is lower than the non-perovskite phase (yellow phase), which is a competitive phase, so that the perovskite phase can be thermodynamically stabilized. Without the dopant, the black phase rapidly collapses into the yellow phase in the air, but the yellow phase does not appear even in air exposure because the black phase becomes more thermodynamically stable through the dopant, and the oxidation reaction to form Cs ₂ SnI ₆ is delayed. Therefore, the structural instability of the CsSnI ₃ material is solved to increase the stability in air. A stable structure can be obtained by applying a dopant to materials having an unstable halide perovskite. It is environmentally friendly because it does not contain lead, and it can utilize a variety of halide perovskite materials.

1 and 2 show the change of the perovskite material according to the introduction of a dopant according to embodiments of the present invention.
3 shows an X-ray diffraction pattern of perovskite material with various exposure times to air.
4 shows the formation energy of the black phase and the yellow phase.
5 to 7 show powder XRD patterns of perovskite materials according to various exposure times to air.
8 shows the absorption spectrum of the perovskite material.
9 shows the bandgap of perovskite material.
10 shows a band structure of black phase perovskite doped with Bi.
11 shows the band structure of Sb doped black phase perovskite.
12-15 show room temperature PL spectra of perovskite materials with various exposure times to air.

Hereinafter, the present invention will be described in detail through examples. The objects, features, and advantages of the present invention will be readily understood through the following examples. The present invention is not limited to the embodiments described herein, but may be embodied in other forms. The embodiments introduced herein are provided to ensure that the disclosed contents are thorough and complete and that the spirit of the present invention is sufficiently transmitted to a person skilled in the art to which the present invention pertains. Therefore, the present invention should not be limited by the following examples.

The dopant for a perovskite material according to embodiments of the present invention is a dopant introduced into a halide perovskite material, and includes one or two or more of compounds SbX ₃ and BiX ₃ . In the formulas SbX ₃ and BiX ₃ , X includes at least one or more of F, Cl, Br, and I.

The perovskite material according to the embodiments of the present invention includes a halide perovskite compound and a dopant introduced into the halide perovskite compound and comprising one or more of compounds SbX ₃ and BiX ₃ do. In the formulas SbX ₃ and BiX ₃ , X includes at least one or more of F, Cl, Br, and I.

Formation of the non-perovskite phase of the perovskite material can be suppressed by the dopant. The perovskite material may maintain a perovskite structure by the dopant.

A method of forming a perovskite material according to embodiments of the present invention includes heating by mixing CsX, SnX ₂ , and a dopant. The dopant includes one or more of compounds SbX ₃ and BiX ₃ , wherein X in the formulas CsX, SnX ₂ , SbX ₃ , and BiX ₃ is at least one or more of F, Cl, Br, and I Includes.

The mixing molar ratio of CsX: SnX ₂ : dopant may be 1: 1: 0.01 to 0.03.

For example, the perovskite material is a dopant in a CsSnI ₃ perovskite compound using solid-state synthesis. SbX ₃ , BiX ₃ (X = F, Cl, Br, I) can be added. For example, the perovskite material is CsI, SnI _2, and BiI ₃ (or SbI ₃₎ a 1: 1 mixture in a molar ratio of 0.01 to 0.03, and about 10 ^- in sealed under ⁴ Torr and about 450 ℃ about It can be formed by heating for 4 hours. The dopant may be added in various molar ratios to the CsSnI ₃ perovskite compound.

For example, the perovskite material can be synthesized by adding 0.00001581 mol of BiI ₃ corresponding to 0.01 times to 0.001581 mol of 1 g of CsSnI ₃ . In addition, the perovskite material having a molar ratio of CsSnI ₃ : BiI ₃ = 1: 0.02 can be synthesized by adding 0.00003163 mol of BiI ₃ corresponding to 0.02 times to 0.001581 mol of 1 g of CsSnI ₃ .

Since the yellow phase is more thermodynamically stable than the black phase, a pure black phase cannot be formed when any impurities are included in the synthesis, and a mixture of yellow and black phases is provided. However, Bi and Sb doping can inhibit yellow phase formation and provide a pure black phase.

1 and 2 show the change of the perovskite material according to the introduction of the dopant according to embodiments of the present invention. Based on CsSnI ₃ 1g, perovskite and dopant molar ratios were tested by adding dopants to CsSnI ₃ : BiI ₃ = 1: 0.01, 0.02, 0.03. Figure 1 shows the change of the X-ray diffraction pattern according to the introduction of the dopant Bi, Figure 2 shows the change of the X-ray diffraction pattern according to the introduction of the dopant Sb.

1 and 2, the yellow phase disappears as the dopant is introduced and has a pure black phase at 3%. Both dopants (BiX ₃ , SbX ₃ ) have the same effect. When Bi is doped, the black phase has lower heat of production than the yellow phase.

When not doped, when exposed to air, the black → yellow → Cs ₂ SnI ₆ phase changes, and the yellow → Cs ₂ SnI ₆ process is an irreversible reaction in which Sn ^{2 +} is oxidized to Sn ^{4 +} , within 2 hours. The above phase change occurs rapidly and all three phases are mixed, and after 12 hours, most of them are oxidized to become Cs ₂ SnI ₆ .

3 shows the X-ray diffraction pattern of the perovskite material according to the exposure time.

Referring to FIG. 3, CsSnI ₃ , CsSnI ₃ + BiI ₃ 3%, and CsSnI ₃ + SbI ₃ 3% sequentially from the left, and when BiI ₃ is doped, black phases exist for up to 40 hours, and a week for SbI ₃ A black phase remains even after it has passed.

When BiX ₃ is doped, the pure black phase is maintained even after 2 hours have elapsed, and a peak of Cs ₂ SnI ₆ is slightly observed after 12 hours, but most of the black phase is still maintained.

In the case of SbX ₃ , a pure black phase is maintained even after 12 hours, and a black phase is present together with the oxidized form Cs ₂ SnI ₆ even after a week.

Since the black phase becomes more stable thermodynamically through the dopant, the yellow phase does not appear even in air exposure, and the oxidation reaction of Cs ₂ SnI ₆ is delayed.

4 shows the formation energy of the black (B-γ) phase and the yellow (Y) phase, and FIGS. 5 to 7 show the powder XRD pattern of the perovskite material according to various exposure times to air. FIG. 5 shows the perovskite material with no dopant introduced, FIG. 6 shows the perovskite material doped with Bi, and FIG. 7 shows the perovskite material doped with Sb.

4 to 7, according to the powder X-ray diffraction (Powder XRD) pattern, the yellow (Y) phase peak decreases as the dopant concentration increases and CsSnI ₃ finally CsI: SnI ₂ : BiI ₃ or SbI _It represents a pure black (B-γ) phase with a ratio of ₃ = 1: 1: 0.03. From the viewpoint of thermodynamic stability, the disappearance of the stable yellow (Y) phase upon doping means that Bi and Sb affect the formation energy of both phases.

When the formation energy of the two phases for evaluating thermodynamic stability during doping is calculated, in the case of pure CsSnI ₃ , the formation energy of the yellow (Y) phase (-4.7229eV / fu) is the black (B-γ) phase (-4.7134eV / fu) is lower than the formation energy. However, after the incorporation of Bi and Sb, the formation energy of the black (B-γ) phase is lower than that of the yellow (Y) phase, and Sb leads to a larger difference between the two phase formation energy than Bi. This means that the black (B-γ) phase is more thermodynamically stable than the yellow (Y) phase when doped, and Sb exhibits a better stability effect than Bi.

The doped black (B-γ) phase can maintain the structure without change to the yellow (Y) phase even under external perturbation, and Bi and Sb doping can block phase transition.

After synthesis of a pure black (B-γ) phase (without a yellow (Y) phase), a phase transition occurs and black (B-γ), yellow (Y) and Cs ₂ SnI ₆ phases coexist within 2 hours after exposure to air. The pure black (B-γ) phase completely loses the perovskite structure within 12 hours. However, the Sb-doped Bi and black (B-γ) phase does not undergo a phase change of the fast onto the yellow (Y), oxidation of Sn ^{+ 2} takes place at a substantially lower rate than the pure sample.

The pure black (B-γ) phase immediately transitions to the yellow (Y) phase after exposure to air. Thereafter, due to the intrinsic properties of the tin element, irreversible oxidation of the yellow (Y) phase proceeds to form Cs ₂ SnI ₆ containing Sn ⁴⁺ cations.

The peaks of the oxidized form Cs ₂ SnI ₆ start appearing in the powder XRD about 12 hours and 18 hours after exposure to air, respectively. The Bi doped black (B-γ) phase decomposes completely within 64 hours, but the Sb doped black (B-γ) phase is still present after a week in air. Therefore, Bi and Sb doping changes the formation energy to block the phase transition path and significantly improves the structural stability of the perovskite structure under air.

FIG. 8 shows the absorption spectrum of the perovskite material, FIG. 9 shows the bandgap of the perovskite material, FIG. 10 shows the band structure of the black phase perovskite doped with Bi, and FIG. 11 Sb-doped black phase perovskite band structure.

8 to 11, in dry air (without H ₂ O), the phase transition of pure CsSnI ₃ and doped CsSnI ₃ is much slower. In particular, samples doped with Bi and Sb do not convert to Cs ₂ SnI ₆ for 24 hours after exposure to dry air. These results indicate that H ₂ O in the air mainly causes decomposition of halide perovskite. Since halide perovskite is an ionic salt, it is difficult to resist H ₂ O. Therefore, doped CsSnI ₃ with H ₂ O protection can make the perovskite structure much more stable.

Bi and Sb doping induces a sharp shift at the absorption edge of the Sn-based perovskite compound, unlike Pb-based materials. The absorption edge of CsSnI ₃ doped with Bi and Sb rapidly changes from 1.3 eV to 0.8 eV and 1.1 eV, respectively, and this band gap change can be observed in a theoretical electron band structure.

Although not shown in the figure, CsSnBr ₃ and MASnBr ₃ and various Sn-based halide page lobe irradiated with the absorption spectrum of the doping of the Sky host material, CsSnBr ₃ and a dopant for MASnBr ₃ is bromide (SbBr ₃ or BiBr _3), such as In the form of, and their absorbing edges change rapidly by doping. On the other hand, in the case of Pb-based halide perovskite materials, Bi and Sb doping does not induce a dramatic change in the absorption edge compared to Sn-based compounds. The absorption edge of a typical Pb-based halide perovskite CsPbBr ₃ decreases slightly from 2.25 eV to 2.0 eV during Bi doping, but does not change during Sb doping.

12-15 show room temperature PL spectra of perovskite materials with various exposure times to air. FIG. 12 shows a perovskite material with no dopant introduced, FIG. 13 shows a perovskite doped with Bi, and FIG. 14 shows a perovskite doped with Sb.

12 to 15, in photoluminescence (PL) characteristics, Bi and Sb doping sharply increases PL intensity without significantly affecting the PL peak position. The tetragonal black CsSnI ₃ shows strong near infrared emission (λ _max = 950 nm) at room temperature, and blue shifted PL (λ _max = 935 nm) is observed. The emission at room temperature upon Bi and Sb doping is almost negligible, but at low temperature (100K) both doped samples exhibit emission at 950 nm.

Although Bi and Sb dopants stiffen PL, CsSnI ₃ with very low concentrations of Bi and Sb keeps the initial PL strength much longer than the undoped samples. Monitoring the PL degradation of doped CsSnI ₃ and pure CsSnI ₃ upon exposure to air, the cumulative PL intensity recorded as pure CsSnI ₃ decreases significantly to half of the initial value after about 30 minutes.

On the other hand, it takes about 2 hours to reduce half of the initial PL of the Bi-doped sample, and the PL intensity of the Sb-doped sample remains almost constant under air for the measurement period. Therefore, the dopants Bi and Sb of the Sn-based halide perovskite improve the air stability of the PL characteristics as well as the perovskite phase.

So far, specific embodiments of the present invention have been described. Those skilled in the art to which the present invention pertains will appreciate that the present invention may be implemented in a modified form without departing from the essential characteristics of the present invention. Therefore, the disclosed embodiments should be considered in terms of explanation, not limitation. The scope of the present invention is shown in the claims rather than the foregoing description, and all differences within the equivalent range should be interpreted as being included in the present invention.

Claims (6)

Halide perovskite compounds which form a non-perovskite phase together with the perovskite phase; And
Introduced in the halide perovskite compound, and comprises a dopant comprising one or more of the compounds SbX ₃ and BiX ₃ ,
In the formulas SbX ₃ and BiX ₃ , X includes at least one or more of F, Cl, Br, and I,
Perovskite material characterized in that the formation of the non-perovskite phase of the perovskite material is suppressed by the dopant. delete delete According to claim 1,
The perovskite material, characterized in that the perovskite material by the dopant maintains a perovskite structure. CsX, SnX ₂ , and mixing the dopant and heating the mixture,
The dopant includes one or more of compounds SbX ₃ and BiX ₃ ,
In the formula CsX, SnX ₂ , SbX ₃ , and BiX ₃ X is F, Cl, Br, and method of forming a perovskite material comprising at least one or more of I. The method of claim 5,
CsX: SnX ₂ : Method of forming a perovskite material, characterized in that the mixing molar ratio of the dopant is 1: 1: 0.01 to 0.03.

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