KR102258124B1 - Method for manufacturing photoactive layer, devices comprising the photoactive layer prepared thereby - Google Patents

Abstract

The present invention includes a method for manufacturing a photoactive layer, which includes: a) preparing a dispersion of bromide-based perovskite quantum dots having a first ligand; b) applying the dispersion on a substrate to form a quantum dot layer; and c) contacting the quantum dot layer with a substitution solution to perform solid-state ligand exchange. The bromide-based perovskite quantum dots is represented by the following formula 1. [Formula 1] AMX_nY_(3-n). In Formula 2, A is a C1-C24 alkyl group, an amine group-substituted alkyl group, or an alkali metal, M is a metal selected from the group consisting of Pb, Cu, Ni, Co, Fe, Mn, Cr, Pd, Cd, Yb, Sn, Ge, and combinations thereof, X is a halogen anion selected from one or more of Br^-, Y is Cl^-, Br^- and I^-, and n is an integer selected from 1 to 3.

Description

Method for manufacturing photoactive layer, devices comprising the photoactive layer prepared thereby {Method for manufacturing photoactive layer, devices comprising the photoactive layer prepared thereby}

The present invention relates to a method of manufacturing a photoactive layer and a device including the photoactive layer manufactured thereby.

Perovskite Quantum Dot (PQD) is a solution process, so manufacturing cost is low, thin film is possible, and due to its excellent optical properties such as high extinction coefficient, it is attracting much attention in the field of light emission and energy. However, since the perovskite quantum dot material is a crystal mainly composed of ionic bonds, it is difficult to utilize the existing quantum dot-related process. In detail, since most of the existing quantum dot-related processes _{use a polar solvent such as water (H 2} O), there is a problem that the perovskite quantum dot material composed of ionic bonds is easily decomposed in the polar solvent. Therefore, in order to improve the stability of the perovskite quantum dot material and to disperse the perovskite quantum dot material well in a non-polar solvent, research on the use of the quantum dot surface treated with a non-conductive long-chain ligand (surfactant), etc. Has been practiced. However, when the perovskite quantum dot material surface-treated with such a long-chain ligand is applied to a light-emitting device or an energy device, the long-chain ligand is non-conductive, so it may interfere with the electrical conduction of the device. There is a problem that lowers it. Therefore, research is required to replace a non-conductive long-chain ligand with a conductive short-chain ligand without deteriorating the excellent optical properties of perovskite quantum dots.

According to this request, the present applicant successfully purified the surface organic ligand (long-chain ligand) of _{CsPbI 3} perovskite quantum dots using a hydrolysis reaction of weakly polar methyl acetate through prior research (non-patent literature). However, it was found that the perovskite quantum dots are decomposed by methanol generated during the hydrolysis reaction. In order to solve this problem, the applicant of the present invention has succeeded in providing improved electrical conduction while effectively purifying the surface organic ligand (long chain ligand) of _{CsPbI 3 perovskite quantum dots using a mixture of methyl acetate and sodium acetate.} It was difficult to apply the mixture to _{systems other than CsPbI 3 perovskite quantum dots.}

Korean Patent Registration No. 10-1815588

Kim, J., Koo, B., Kim, WH, Choi, J., Choi, C., Lim, SJ, Lee, JS, Kim, DW, Ko, MJ, Kim, Y. Alkali acetate-assisted enhanced electronic coupling in CsPbI3 perovskite quantum dot solids for improved photovoltaics. Nano Energy (2019), 104 130.

The present invention provides a method of manufacturing a photoactive layer that is chemically stable and homogeneously formed while improving photovoltaic properties, and a device including the photoactive layer manufactured thereby.

The present invention comprises the steps of: a) preparing a dispersion of bromide-based perovskite quantum dots having a first ligand; b) applying the dispersion on a substrate to form a quantum dot layer; And c) contacting the quantum dot layer with a substitution solution to perform solid-state ligand exchange.

In this case, the bromide-based perovskite quantum dots may be represented by Formula 1 below.

[Formula 1]

AMX _n Y _3-n

In Chemical Formula 2,

A is a C1-C24 alkyl group, an amine-substituted alkyl group, or an alkali metal,

M is a metal selected from the group consisting of Pb, Cu, Ni, Co, Fe, Mn, Cr, Pd, Cd, Yb, Sn, Ge, and combinations thereof,

X is Br ^- and

Y is Cl ^- is a halogen anion selected from one or _more, ^-, Br ^- and I

n is an integer selected from 1 to 3.

In one aspect of the present invention, the above-described substitution solution may be a mixture of an ester-based solvent represented by the following formula (2) and an alkali metal acetate salt.

[Formula 2]

In Formula 1,

R ¹ is a C1 to C6 linear or branched alkyl group,

R ² is a C1 to C6 linear or branched alkyl group.

In one aspect of the present invention, the alkali metal acetate salt described above may be potassium acetate, sodium acetate, lithium acetate, rubidium acetate, cesium acetate, or a mixture thereof.

In one aspect of the present invention, upon the above-described solid-state ligand exchange, the first ligand of the perovskite quantum dot may be substituted with the second ligand resulting from the above-described substitution solution.

In one aspect of the present invention, the above-described second ligand may have a shorter chain length than the above-described first ligand.

In one aspect of the present invention, the above-described first ligand may be one or more selected from oleate, oleylammonium, and oleylamine.

In a specific aspect of the present invention, the above-described solvent includes a mixed solvent of a first ester-based solvent and a second ester-based solvent having different dielectric constants, and may satisfy Equation 1 below.

[Equation 1]

D1/D2 <1

In Equation 1 above,

D1 is the dielectric constant of the first acetate-based solvent, and D2 is the dielectric constant of the second acetate-based solvent.

In one aspect of the present invention, the dispersion medium of the dispersion liquid described above may be a non-polar solvent.

In one aspect of the present invention, the thickness of the photoactive layer may be 180 to 250 nm.

The present invention provides a device including a photoactive layer manufactured by the method for manufacturing the photoactive layer described above. At this time, the perovskite quantum dots included in the above-described photoactive layer emits green light, and the emission peak wavelength of the green light may be 495 to 565 nm.

The manufacturing method of the photoactive layer according to the present invention is excellent in chemical stability by replacing the long-chain organic ligand surrounding the bromide-based perovskite quantum dots with a ligand of a shorter chain length in a solid phase, and has excellent chemical stability and homogeneous perovskite quantum dots. A photoactive layer distributed in a manner can be prepared, and when used as a light emitting device and an energy device by using the prepared photoactive layer, the open circuit voltage (V _OC ), the short circuit current density (J _SC ), the charge factor (FF) and There is an advantage in that photovoltaic characteristics such as photoelectric conversion efficiency (PCE) are remarkably improved.

1 is an X-ray photoelectron spectroscopy (XPS) analysis result of a photoactive layer substituted with a solid ligand according to an embodiment of the present invention.
2 is a photoluminescence (PL) characteristic analysis result of a photoactive layer substituted with a solid ligand according to an embodiment of the present invention.
3 is an analysis result of UV-vis Absorption Spectroscopy of a photoactive layer substituted with a solid ligand according to an embodiment of the present invention.
4 is a surface atomic force microscope (AFM) analysis result of a photoactive layer substituted with a solid ligand according to an embodiment of the present invention.
5 is a cross-sectional SEM analysis result and schematic diagram of a perovskite solar cell according to an embodiment of the present invention.
6 is an electroluminescence (EL) analysis result of a perovskite solar cell according to Example 6 of the present invention.

Hereinafter, a method of manufacturing a photoactive layer of the present invention and a device including the photoactive layer manufactured thereby will be described in detail with reference to the accompanying drawings. The drawings introduced below are provided as examples in order to sufficiently convey the spirit of the present invention to those skilled in the art. Accordingly, the present invention is not limited to the drawings presented below and may be embodied in other forms, and the drawings presented below may be exaggerated to clarify the spirit of the present invention. At this time, unless there are other definitions in the technical terms and scientific terms used, they have the meanings commonly understood by those of ordinary skill in the technical field to which this invention belongs, and the gist of the present invention in the following description and accompanying drawings. Descriptions of known functions and configurations that may be unnecessarily obscure will be omitted. In addition, the singular form used in the specification and the appended claims may be intended to include the plural form unless otherwise indicated in the context. Units used in this specification and the appended claims are based on weight, and as an example, the unit of% or ratio means weight% or weight ratio.

As described above, in order to manufacture high-quality perovskite quantum dots having material stability and high dispersibility in polar solvents, the surface of the quantum dots must be treated with a non-conductive long-chain ligand. When the perovskite quantum dot material surface-treated with such a long-chain ligand is applied to a light-emitting device or an energy device, the long-chain ligand may interfere with electrical conduction of the device as it is non-conductive, thereby reducing the performance of the device. There is a problem to let you.

Through prior research, the present applicant used a mixture of an ester-based solvent (methyl acetate) and an alkali metal acetate salt (sodium acetate) to use a non-conductive organic ligand (long chain ligand) present on the surface of _{CsPbI 3 perovskite quantum dots.} Using a conductive organic ligand (short-chain ligand) by solid-state ligand exchange (solid-state ligand exchange), it was possible to provide a _{CsPbI 3 perovskite quantum dot having improved electrical conduction.} However, it was difficult to apply this process to _{systems other than CsPbI 3 perovskite quantum dots.}

Accordingly, in the course of conducting a study on the solid-state ligand exchange of bromide-based perovskite quantum dots, the applicant of the present invention has demonstrated the synergistic effect of heterogeneous ester solvents with different polarities and alkali metal acetate salts. As a result of in-depth research, the present invention was completed by discovering a solid-state ligand exchange system from a non-conductive first ligand included in a bromide-based perovskite quantum dot to a conductive second ligand. Reached.

At this time, the bromide-based perovskite quantum dots specified in the present invention may be represented by Formula 1 below.

[Formula 1]

AMX _n Y _3-n

In Chemical Formula 2,

A is a C1-C24 alkyl group; An amine group substituted C1-C24 alkyl group; Or an alkali metal selected from one or more of Li, Na, K, Rb, Cs and Fr; and,

M is a metal selected from the group consisting of Pb, Cu, Ni, Co, Fe, Mn, Cr, Pd, Cd, Yb, Sn, Ge, and combinations thereof,

X is Br ^- and

Y is Cl ^- is a halogen anion selected from one or _more, ^-, Br ^- and I

n is an integer selected from 1 to 3.

The method of manufacturing a photoactive layer according to the present invention based on the above-described invention comprises the steps of: a) preparing a dispersion of bromide-based perovskite quantum dots having a first ligand; b) applying the dispersion on a substrate to form a quantum dot layer; And c) contacting the quantum dot layer with the substitution solution to perform solid-state ligand exchange.

Here, the first ligand included in the bromide-based perovskite quantum dot is the inside and the surface of the perovskite quantum dot to passivate the perovskite quantum dot when synthesizing the perovskite quantum dot by a chemical wet method. And both, which prevents the perovskite quantum dots from agglomerating and immobilizes them to maintain a stable structure, but as they are non-conductive, they cause a decrease in electrical conduction of the photoactive layer. However, the manufacturing method of the photoactive layer according to the present invention uses a solution coating method, which is an inherent advantage of perovskite quantum dots, while using a non-conductive first ligand present on the surface of a bromide-based perovskite quantum dot. It can be removed by solid-state ligand exchange with a conductive second ligand having a shorter chain length than the first ligand, and a non-conductive first ligand (long-chain ligand) while passivating perovskite quantum dots. ), it is good that it is possible to remarkably increase the electrical conductivity of the photoactive layer by solving the problems (deterioration of electrical conduction, etc.), and such a process is very simple, and thus the process cost is inexpensive. Furthermore, when using a perovskite quantum dot with improved electrical conductivity as a photoactive layer of a light-emitting device or an energy device in the future, in the case of a device including a photoactive layer (light-emitting device and energy device, etc.), improved photovoltaic properties (open circuit voltage) (V _OC ), short-circuit current density (J _SC ), charge factor (FF), photoelectric conversion efficiency (PCE), etc.).

In one embodiment, the first ligand described above is oleic acid, oleylamine, TOP (trioctylphosphine), TOPO (trioctylphosphine oxide), octylamine, trioctyl amine, It may be hexadecylamine, hexylphosphonic acid (HPA), tetradecylphosphonic acid (TDPA), octylphosphinic acid (OPA), etc., and one or more selected from oleic acid or oleylamine. However, it is not limited thereto.

According to an aspect of the present invention, in the above-described solid-state ligand exchange, the second ligand is derived from the above-described substitution solution, and may be an acetate (OAc) ion.

In one embodiment, the above-described substitution solution may be a mixture of an ester-based solvent and an alkali metal acetate salt.

In detail, the ester-based solvent described above may be represented by the following formula (2).

[Formula 2]

In Formula 1,

R ¹ is a C1 to C6 linear or branched alkyl group, specifically a C1 to C4 linear or branched alkyl group,

R ² is a C1 to C6 linear or branched alkyl group, specifically R ² is CH ₃ .

In a preferred embodiment, the above-described ester-based solvent includes a mixed solvent of a first ester-based solvent and a second ester-based solvent having different dielectric constants, and may satisfy Equation 1 below.

[Equation 1]

D1/D2 <1

In Equation 1 above,

D1 is the dielectric constant of the first acetate-based solvent, and D2 is the dielectric constant of the second acetate-based solvent.

Thus, the method of manufacturing a photoactive layer according to the present invention is a bromide-based perovskite by using a heterogeneous acetate-based solvent having a different polarity as a solid-phase ligand substitution solution of the first ligand in a bromide-based perovskite quantum dot. The miscibility between the quantum dots and the substitution solution is better, and there is an effect that the solid-phase ligand substitution is made more effectively.

In one embodiment, the alkali metal acetate salt described above may be potassium acetate, sodium acetate, lithium acetate, rubidium acetate, cesium acetate, or a mixture thereof, but is not limited thereto.

In one embodiment, the dispersion medium of the above-described dispersion is a non-polar solvent, specifically, the non-polar solvent is an organic solvent having a solubility of less than 0.1 M, less than 0.01 M, or less than 0.001 M of the perovskite compound under 1 atmosphere of 20°C. I can. As a specific example, the non-solvent is chloroform, hexene, cyclohexene, 1,4-dioxane, benzene, toluene, hexane ), triethylamine, chlorobenzene, ethylamine, diethylether, ethylacetate, acetic acid, 1,2-dichlorobenzene ( 1,2-Dichlorobenznene), Tert-butyl alcohol (Tert-Butyl alcohol), 2-butanol (2-Butanol), isopropanol (Isopropanol) and methyl ethyl ketone (Methylethylketone) may be one or two or more selected from, but this It is not limited, and an organic solvent that is not decomposed due to ionization of perovskite quantum dots is sufficient.

In one embodiment, the thickness of the photoactive layer may be 180 to 250 nm, specifically 180 to 230 nm, and more specifically 190 to 210 nm, but is not limited thereto. However, when the photoactive layer satisfies the above-described thickness, it may have remarkably excellent photovoltaic properties.

As a non-limiting example, the substrate is not particularly limited as long as it is a rigid substrate or a flexible substrate capable of forming a coating film of a dispersion of perovskite quantum dots, but transparent substrates such as glass and plastic films, and opaque such as silicon wafers. One substrate can be used. As an example, the substrate may be a semiconductor, ceramic, metal, polymer, or a laminate in which two or more materials selected from these materials are stacked as each layer, but is not limited thereto.

Further, the present invention includes a device including a photoactive layer manufactured by the method for manufacturing the photoactive layer described above.

Specifically, the present invention includes an energy device (solar cell), an electronic device (transistor, etc.), a light-emitting device (light-emitting diode, etc.), a memory device or a sensor including a photoactive layer manufactured by the method for manufacturing the photoactive layer described above. can do.

As an example, when the above-described device is an energy device (solar cell),

The solar cell according to the present invention includes a first electrode; Major delivery layer; The photoactive layer described above; Electron transport layer; And a second electrode; may have a structure in which they are sequentially stacked.

As a non-limiting example, among the above-described first and second electrodes, an electrode on a side to which light is incident may be a transparent electrode. The transparent electrode is a transparent conductive oxide such as fluorine-containing tin oxide (FTO; Fouorine doped Tin Oxide) or indium-containing tin oxide (ITO; Indium doped Tin Oxide), or CNT (carbon nanotube), graphene, and metal nanowires. It may be an electrode based on a nanostructure such as. The rear electrode, which is an electrode facing the transparent electrode, may be an electrode based on gold, silver, platinum, palladium, copper, aluminum, carbon, cobalt sulfide, copper sulfide, nickel oxide, etc., but is not limited thereto.

As a non-limiting example, the concrete material and structure of the electron transport layer and the major transport layer are not particularly limited, but holes and electrons are moved in a conventional perovskite solar cell using perovskite quantum dots as a light absorber. It suffices if it is a material and structure for making it.

As a non-limiting example, the electron transport layer is an electron conductive metal oxide, specifically, a metal oxide, titanium oxide, zinc oxide, tin oxide, niobium oxide, molybdenum oxide, magnesium oxide, aluminum oxide, vanadium oxide. And composite oxides thereof, but are not limited thereto. In addition, the above-described hole transport layer is a hole-conductive organic material, specifically spiro-OMeTAD (2,2',7,7'-tetrakis (N,N-di-p-methoxyphenylamine)-9,9-spirobifluorene), P3HT ( poly[3-hexylthiophene]), PEDOT (poly(3,4-ethylenedioxythiophene)), PEDOT:PSS (poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate)), PTAA (poly(triarylamine)), Poly(4- butylphenyl-diphenyl-amine) and the like, but are not limited thereto.

At this time, the above-described electron transport layer and the hole transport layer may have a structure in which a dense thin film or a dense thin film and a porous film are stacked independently of each other, and the thickness of the electron transport layer and the hole transport layer is 20 to 80 nm and 150 to 250 nm, respectively. It may be, but is not necessarily limited thereto.

The present invention includes a perovskite solar cell module in which two or more of the aforementioned perovskite solar cells are connected in series and/or in parallel.

The present invention includes a device in which power is supplied by the perovskite solar cell described above.

In one embodiment, when a constant voltage is applied to the above-described perovskite solar cell, the above-described solar cell may have green light emission characteristics. That is, the photoactive layer according to the present invention can also be used for light-emitting devices (light-emitting diodes, etc.). At this time, the emission peak (eg, the maximum emission peak) wavelength of green light may be 480 to 580 nm, specifically 495 to 565 nm.

Hereinafter, the present application will be described in more detail using examples, but the following examples are merely illustrative to aid understanding of the present application, and the contents of the present application are not limited to the following examples.

(Example 1)

Step 1: CsPbBr ₃ Preparation of PQD (Perovskite Quantum Dot) dispersion

Step 1-1: Preparation of Cs-oleate solution

0.407 g cesium carbonate (CsCO ₃ , Alfa Aesar), 20 mL 1-Octadecene (ODE, technical grade, Sigma Aldrich) and 1.25 mL oleic acid (OA, technical grade, Alfa Aesar) Were mixed in the flask. The mixture was degassed at 120° C. for 30 minutes, and then purged with Ar, an inert gas, and this process was repeated three times to obtain a Cs-oleate solution.

Step 1-2: PbBr ₂ Solution preparation

0.4 g of lead bromide (lead (II) bromide, PbBr ₂ , Alfa Aesar) and 25 mL of 1-octadecene were mixed in a flask, followed by degassing at 120° C. for 30 minutes. 1.5 mL of oleic acid and 1.5 mL of oleyl amine (Oleylamine, technical grade, Sigma Aldric) were added to the mixture, followed by degassing for an additional 30 minutes to completely dissolve, followed by purging with Ar, an inert gas. Thus, a PbBr ₂ solution was obtained.

Step 1-3: CsPbBr ₃ PQD synthesis and CsPbBr ₃ PQD dispersion preparation

After increasing the temperature of the prepared PbBr ₂ solution to 185° C., 2 mL of Cs-oleate solution was rapidly added to the flask containing the _{PbBr 2 solution, and then cooled to room temperature to prepare a mixed solution.} 60 mL of methyl acetate (MeOAc, Duksan) was added to the mixture and centrifuged at 5000 rpm for 10 minutes, and then the supernatant was removed to obtain a first precipitate. The first precipitate was dispersed in 12 mL of hexane, 20 mL of MeOAc was added to the dispersion, and then centrifuged again at 5000 rpm for 5 minutes to obtain a second precipitate from which the supernatant was removed. The secondary precipitate was again dispersed in 30 mL of hexane, and the dispersion was filtered through a plastic syringe attached with a 0.2 um PTFE filter. The filtered CsPbBr ₃ PQD was re-degassed and redispersed in n-octane at a concentration of 75 mg mL ^-1 to prepare a _{CsPbBr 3 PQD dispersion.}

Step 2: Perovskite solar cell manufacturing

Step 2-1: substrate preparation

FTO (F-doped SnO ₂ )-deposited glass substrate (hereinafter, FTO substrate) is sequentially ultrasonicated for 15 minutes in water for cleaning, deionized water, acetone and 2-propanol, respectively, and then UV/O ₃ It was prepared by UV treatment for 20 minutes using the device.

Step 2-2: Formation of Electron Transport Layer

_{After spin-coating a c-TiO 2} precursor solution (Ti-alkoxide, SC-BT060, Sharechem) at 3000 rpm for 30 seconds on the FTO substrate of step 2-1, pre-heat treatment at 150° C. for 10 minutes in an air atmosphere And heat treatment at 500° C. for 1 hour, cooling to room temperature _{, immersion in 120 mM TiCl 4} solution, heat treatment at 70° C. for 30 minutes, washing with deionized water, and heat treatment again at 500° C. for 1 hour. A c-TiO ₂ -coated FTO substrate (hereinafter, c-TiO ₂ /FTO substrate) was obtained.

Step 2-3: Forming a photoactive layer

First, sodium acetate (NaOAc, Sigma Aldrich) was diluted in methyl acetate (MeOAc) to prepare a replacement solution. At this time, the concentration of sodium acetate in the replacement solution is 1 mg/mL. Next, the CsPbBr3 PQD dispersion prepared in step 1-3 was _{applied collectively to the rotation center of the c-TiO 2} /FTO substrate, and spin-coated at 1000 rpm for 20 seconds and 2000 rpm for 5 seconds to form _{a CsPbBr 3 PQD film} I did. The formed CsPbBr ₃ PQD film was immersed in the substitution solution for 15 seconds, then spin-dried at 2000 rpm for 10 seconds, washed with MeOAc, and then spin-dried again at 2000 rpm for 10 seconds, thereby replacing the solid ligand. A CsPbBr ₃ PQD film (hereinafter, substituted CsPbBr ₃ PQD film) was formed. At this time, the layer by layer (LBL) process was repeated several times so that the photoactive layer had a thickness of 200 nm.

Step 2-4: Formation of the hole transport layer

First, 72.3 mg of 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene (Spiro-OMeTAD, Lumtec), 28.8 μL of 4-tert-butylpyridine (4-TBP, Sigma Aldrich) and 17.5 μL of lithium bis (trifluoromethylsulfonyl) imide (Li-TFSI, Alfa Aesar) solution was dissolved in 1 mL of chlorobenzene (anhydrous, Sigma Aldrich) to prepare a Spiro-OMeTAD solution. . Next, the Spiro-OMeTAD solution was spin-coated at 4000 rpm for 25 seconds on the substituted CsPbBr _{3 PQD film prepared in step 2-3.} At this time, the process was performed while controlling the humidity condition between 20% and 30%.

Step 2-5: Formation of an electrode and a buffer layer

A perovskite solar cell was manufactured by depositing an Au electrode having a thickness of about 120 nm on the hole transport layer of the substrate and a MoO _{x buffer layer having a thickness of about 15 nm on a glass substrate through thermal evaporation.}

(Example 2)

In step 2-3 of Example 1, the same method as in Example 1 was used, except that sodium acetate was diluted with ethyl acetate (EtOAc, Duksan) as a substitute solution.

(Example 3)

In step 2-3 of Example 1, the same method as in Example 1 was used, except that sodium acetate was diluted with propyl acetate (PrOAc, Duksan) as a substitute solution.

(Example 4)

In step 2-3 of Example 1, the same method as in Example 1 was used, except that sodium acetate was diluted with butyl acetate (BtOAc, Duksan) as a substitute solution.

(Example 5)

In step 2-3 of Example 1, the same method as in Example 1 was used, except that sodium acetate was diluted in a mixed solvent (weight ratio of ethyl acetate and butyl acetate = 9: 1) as a substitute.

(Example 6)

In step 2-3 of Example 1, the same method as in Example 1 was used, except that sodium acetate was diluted in a mixed solvent (weight ratio of ethyl acetate and butyl acetate = 8: 2) and used as a substitute.

(Example 7)

In step 2-3 of Example 1, the same method as in Example 1 was used, except that sodium acetate was diluted in a mixed solvent (weight ratio of ethyl acetate and butyl acetate = 6:4) as a substitute.

(Comparative Example 1)

In step 2-3 of Example 1, the same method as in Example 1 was used, except that the process using the substitute solution was not performed.

(Comparative Example 2)

In step 2-3 of Example 1, the same method as in Example 1 was used, except that methyl acetate was used as the substitute solution.

(Comparative Example 3)

In step 2-3 of Example 1, the same method as in Example 1 was used, except that ethyl acetate was used as the substitute solution.

(Comparative Example 4)

In step 2-3 of Example 1, the same method as in Example 1 was used, except that only propyl acetate was used as the substitute solution.

(Comparative Example 5)

In step 2-3 of Example 1, the same method as in Example 1 was used, except that butyl acetate was used as the substituent.

(Comparative Example 6)

In step 2-3 of Example 1, as a substitution solution, only sodium acetate was diluted in methanol (MeOH) and only used was excluded, except that butyl acetate (EtOAc) was used, and the same method as in Example 1 was used.

(Comparative Example 7)

In step 1-2 of Example 1, when manufacturing perovskite quantum dots, except for using lead iodide (lead (II) iodide, PbI ₂ , Alfa Aesar) _{instead of lead bromide (PbBr 2 ), Example} The same method as in 1 was used.

1 is an X-ray photoelectron spectroscopy (XPS) analysis result of a photoactive layer substituted with a solid ligand according to an embodiment of the present invention. At this time, in the drawing, the As-cast film is Comparative Example 1, MeOAc with NaOAc is Example 1, EtOAc with NaOAc is Example 2, PrOAc with NaOAc is Example 3, and BtOAc with NaOAc is Example 4. As shown, it can be observed that the examples in which solid-phase ligand substitution is performed show lower intensity with respect to the C1s peak than Comparative Example 1 in which the solid-phase ligand substitution is not performed. In particular, it can be seen that the intensity of the C1s peak decreases as the length of the alkyl chain of the alkyl acetate mixed with the substituent increases. This is because solvent miscibility increases as the alkyl chain length of the alkyl acetate mixed in the substituent increases, so that the long-chain ligands (oleate and oleylammonium ligands) in the PQD forming the photoactive layer become the short-chain ligands (acetate ligand) in the substitution solution. It means more efficient substitution.

2 is a photoluminescence (PL) characteristic analysis result of a photoactive layer substituted with a solid ligand according to an embodiment of the present invention. In detail, (a) of FIG. 2 is a PL spectrum of Comparative Examples 2 to 5, and (b) of FIG. 2 is a PL spectrum of Examples 1 to 4. As shown, regardless of the presence or absence of NaOAc in the substitution solution, it can be seen that the range of the PL peak is constant at 495 to 565 nm, but in the case of embodiments, it can be seen that it has a narrower half-width (FWHM). . This means that the examples have better color purity than the comparative examples. In particular, in the case of Examples, unlike Comparative Examples, as the alkyl chain length of the carbosylate ester-based compound increases, it can be seen that the PL peak is red shifted (long wavelength shift). This is because the solvent miscibility of the substitution solution (including NaOAc) according to the examples is superior to that of the substitution solution (not including NaOAc) of the comparative examples, so that solid-state ligand substitution occurs more easily and the distance between particles is shortened. It means more functional.

3 is an analysis result of UV-vis Absorption Spectroscopy of a photoactive layer substituted with a solid ligand according to an embodiment of the present invention. In detail, Figure 3 (a) is Comparative Example 2, Figure 3 (b) is Comparative Example 3, Figure 3 (c) is Comparative Example 4, Figure 3 (d) is Comparative Example 5 , FIG. 3(e) is Example 1, FIG. 3(f) is Example 2, FIG. 3(g) is Example 3, and FIG. 3(h) is Example 4. As shown, regardless of the presence or absence of NaOAc in the substitution solution, it can be seen that the absorption range is 495 nm or less, but the examples have a much higher absorbance than the comparative example. In particular, looking at the inset, it can be seen that the absorbance measured at 485 nm increases somewhat linearly compared to the comparative examples according to the function of the number of stacks of the photoactive layer. This means that the solid-state ligand-substituted photoactive layer prepared according to the embodiments has a uniform surface shape regardless of the thickness of the solid-state ligand, even if the solid-state ligand is substituted through a layer by layer (LBL) process. .

4 is a surface atomic force microscope (AFM) analysis result of a photoactive layer substituted with a solid ligand according to an embodiment of the present invention. In detail, (a) of FIG. 4 is Comparative Example 2, (b) of FIG. 4 is Comparative Example 3, (c) of FIG. 4 is Comparative Example 4, and (d) of FIG. 4 is Comparative Example 5. 4(e) is Example 1, FIG. 4(f) is Example 2, FIG. 4(g) is Example 3, and FIG. 4(h) is Example 4. As shown, it can be seen that the photoactive layer of the comparative examples is manufactured in a form having holes due to the melting of the bottom layer, whereas the examples are formed of a perovskite quantum dot layer that is more or less homogeneously distributed than the comparative examples. These results are consistent with the results of the UV-Vis spectrum analysis of FIG. 3.

5 is a cross-sectional SEM analysis result and schematic diagram of a perovskite solar cell according to an embodiment of the present invention. As shown, the perovskite solar cell manufactured according to the temporary example includes a glass substrate of about 2.5 mm thickness, an FTO electrode of about 300 nm thickness, an electron transport layer of about 50 nm thickness (TiO ₂ in the drawing), A photoactive layer about 200 nm thick (CsPbBr3 PQDs in the figure), a hole transport layer about 250 nm thick (Spiro-MeOTAD in the figure), a buffer layer about 15 nm thick (MoO _x in the figure) and about 120 nm thick It can be seen that it is composed of Au electrodes.

Table 1 is a photovoltaic parameter analysis result of a perovskite solar cell according to an embodiment of the present invention. As shown, it can be seen that the open circuit voltage (V _OC ), short-circuit current density (J _SC ), charge factor (FF), and photoelectric conversion efficiency (PCE) of the embodiments are all superior to those of the comparative examples. This difference in photovoltaic characteristics (performance) is due to the characteristics of the perovskite chemical film included in each light absorbing layer. In detail, in the case of the examples, the solvent miscibility of the ligand substitution solution is better than that of the comparative examples, and the long-chain ligand in the photoactive layer, which causes a decrease in the performance of the perovskite solar cell, is more efficiently replaced with a short-chain ligand in the solid phase. can be removed, has a higher V _oc and FF, because of such a high V _oc and FF have improved PEC.

In Comparative Example 1, CsPbBr ₃ perovskite quantum dots (hereinafter, CsPbBr ₃ PQD) was electric conduction of the photoactive layer of the base is too low could not be made of the solar cell element, in the case of Comparative Examples 2 to 6 CsPbB ₃ The miscibility of PQD and ester solvent was very high, and CsPbB ₃ PQD was rather washed away during the LBL process, making it impossible to laminate to a desired thickness.

6 is an electroluminescence (EL) analysis result of a perovskite solar cell according to Example 6 of the present invention. As shown, it can be observed that the green light emission EL characteristics of the perovskite solar cell according to Example 6 increase as a function of the applied external DC voltage, and the emission peak wavelength of green light is 495 to 565 nm. That is, it can be seen that the perovskite solar cell according to the sixth embodiment has a green light emission characteristic at a low turn-on voltage of 2.4 V or more. Although not shown, it was confirmed that the EL characteristics of the perovskite solar cell according to Examples other than Example 6 had similar results. Accordingly, the photoactive layer substituted with the solid ligand according to the present invention can be utilized as a light emitting diode in addition to a perovskite solar cell.

As described above, in the present invention, specific matters and limited embodiments and drawings have been described, but this is provided only to help a more general understanding of the present invention, and the present invention is not limited to the above embodiments, and the present invention is Those of ordinary skill in the relevant field can make various modifications and variations from these descriptions.

Accordingly, the spirit of the present invention is limited to the described embodiments and should not be defined, and all things that are equivalent or equivalent to the claims as well as the claims to be described later fall within the scope of the inventive concept. .

Claims (11)

a) preparing a dispersion of bromide-based perovskite quantum dots having a first ligand;
b) forming a quantum dot layer by applying the dispersion on a substrate; And
c) contacting the quantum dot layer with a substitution solution, which is a mixture of an ester-based solvent and an alkali metal acetate salt, to perform solid-state ligand exchange; and,
The bromide-based perovskite quantum dots are represented by the following formula (1), a method of manufacturing a photoactive layer.
[Formula 1]
AMX _n Y _3-n
In Formula 1,
A is a C1-C24 alkyl group, an amine-substituted alkyl group, or an alkali metal,
M is a metal selected from the group consisting of Pb, Cu, Ni, Co, Fe, Mn, Cr, Pd, Cd, Yb, Sn, Ge, and combinations thereof,
X is Br ^- and
Y is Cl ^- is a halogen anion selected from one or _more, ^-, Br ^- and I
n is an integer selected from 1 to 3. The method of claim 1,
The method of manufacturing a photoactive layer, wherein the substitution solution is a mixture of an ester-based solvent and an alkali metal acetate salt represented by the following Chemical Formula 2.
[Formula 2]

In Chemical Formula 2,
R ¹ is a C1 to C6 linear or branched alkyl group,
R ² is a C1 to C6 linear or branched alkyl group. The method of claim 2,
The method for producing a photoactive layer, wherein the alkali metal acetate salt is potassium acetate, sodium acetate, lithium acetate, rubidium acetate, cesium acetate, or a mixture thereof. The method of claim 1,
When the solid-state ligand exchange is performed, the first ligand of the perovskite quantum dot is replaced with a second ligand resulting from the substitution solution. The method of claim 4,
The second ligand will have a shorter chain length than the first ligand, the method of manufacturing a photoactive layer. The method of claim 1,
The first ligand is one or more selected from oleate, oleylammonium, and oleylamine, a method for producing a photoactive layer. The method of claim 2,
The ester-based solvent includes a mixed solvent of a first ester-based solvent and a second ester-based solvent having different dielectric constants, and satisfies the following formula (1).
[Equation 1]
D1/D2 <1
In Equation 1 above,
D1 is the dielectric constant of the first ester solvent,
D2 is the dielectric constant of the second ester solvent. The method of claim 1,
The dispersion medium of the dispersion is a non-polar solvent, a method for producing a photoactive layer. The method of claim 1,
The thickness of the photoactive layer is 180 to 250 nm, the method of manufacturing a photoactive layer. A device comprising a photoactive layer manufactured by the manufacturing method according to any one of claims 1 to 9. The method of claim 10,
The perovskite quantum dots included in the photoactive layer emits green light, and the emission peak wavelength of green light is 495 to 565 nm.

Images