KR20190079136A - A perovskite solar cell with improved safety - Google Patents

Abstract

The present invention relates to a perovskite solar cell with improved safety as interface characteristics between a light absorbing layer and a hole transport layer are improved. More specifically, the perovskite solar cell with improved safety comprises: a support substrate; a first electrode formed on the support substrate; an electrode transport layer formed on the first electrode; a light absorbing layer formed on the electrode transport layer and including a perovskite compound having a cubic crystal structure; a hole transport layer formed on the light absorbing layer and including hole transport materials; and a second electrode formed on the hold transport layer wherein an interface is formed between the light absorbing layer and the hole transport layer. The interface includes: a first interface in which an orientation angle of a crystal plane of the perovskite compound is in the range of 20-30° with respect to a plane of the support substrate; and a second interface in which an orientation angle of a crystal plane of the perovskite compound is in the range of 50-60° with respect to the plane of the support substrate.

Description

A PEROVSKITE SOLAR CELL WITH IMPROVED SAFETY BACKGROUND OF THE INVENTION [0001]

The present invention relates to a perovskite solar cell having improved interfacial characteristics between a light absorbing layer and a hole transporting layer and having high safety.

Perovskite solar cells are solid state solar cells based on perovskite (ABX ₃ ) light absorbing materials.

Perovskite solar cells have a very high extinction coefficient and can effectively absorb sunlight even at submicrometer thickness. As a result, the power conversion efficiency (PCE) is about 20% It is getting attention.

As a part of this, Korean Patent No. 10-1543438 improves photoelectric conversion efficiency by adding a conductive filler such as a carbon nanotube to a hole transport layer of a perovskite solar cell.

In addition, Korean Patent No. 10-1578875 introduces a hole blocking layer in a perovskite solar cell to facilitate the movement of electrons.

However, the perovskite solar cell according to the related art as described above has a problem in that Spiro-OMeTAD ((2,2 ', 7,7'-tetrakis (N, N-di- Phenylamine) 9,9'-spirobifluorene)), PTAA (poly (triarylamine)), and the like.

In order to apply perovskite solar cells to automobiles, it is necessary to integrate them into vehicle parts by using a bonding film. At this time, the process temperature rises to 110 ° C or more. When the vehicle starts to run, the temperature rises to about 100 ° C.

Conventional hole transport materials such as Spiro-OMeTAD and PTAA exhibit phase transition (thermal transition) at about 90 to 120 ° C, resulting in a sudden drop in photoelectric conversion efficiency, deterioration in interfacial adhesion, and delamination from the light absorption layer Which can not be applied to automotive perovskite solar cells.

Korean Patent No. 10-1543438 Korean Patent No. 10-1578875

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems and limitations of the prior art.

It is an object of the present invention to provide a perovskite solar cell including a hole transporting layer composed of a hole transporting material having excellent heat resistance and durability.

It is also an object of the present invention to provide a perovskite solar cell having a high photoelectric conversion efficiency and improved interfacial adhesion between the hole transport layer and the light absorption layer.

The object of the present invention is not limited to the above-mentioned object. The objects of the present invention will become more apparent from the following description, which will be realized by means of the appended claims and their combinations.

A perovskite solar cell having improved stability according to the present invention includes a support substrate, a first electrode formed on the support substrate, an electron transport layer formed on the first electrode, a second electrode formed on the electron transport layer, ) Crystal structure, a hole transporting layer formed on the light absorbing layer and including a hole transporting material, and a second electrode formed on the hole transporting layer, wherein the light absorbing layer comprises a perovskite compound, And an interface between the hole transporting layer and the hole transporting layer is formed, and the interface includes a first interface having an orientation angle of the crystal plane of the perovskite compound with respect to the surface of the support substrate of 20 to 30 degrees; And a second interface in which the orientation angle of the crystal plane of the perovskite compound with respect to the surface of the support substrate is 50 ° to 60 °.

The perovskite compound may be represented by the following general formula (1).

[Chemical Formula 1]

ABX ₃

Here, A is selected from the group consisting of Formamidinium (FA), Methylammonium (MA), and combinations thereof, and B is selected from the group consisting of lead (Pb), tin (Sn) And X is selected from the group consisting of chlorine (Cl), bromine (Br), iodine (I), and combinations thereof.

The hole transport material may be a compound having a unit structure represented by the following formula (2).

(2)

ML

Here, M is a metal selected from the group consisting of copper (Cu), zinc (Zn), iron (Fe), magnesium (Mg), cobalt (Co), nickel (Ni) Is a phthalocyanine-based ligand compound that is coordinatively bonded to the (M) ion.

The hole transport material may be a compound having a unit structure represented by the following formula (3).

(3)

Wherein M may be selected from the group consisting of copper (Cu), zinc (Zn), iron (Fe), magnesium (Mg), cobalt (Co), nickel (Ni) the or may be a unsubstituted C _{1 -20} alkyl.

The hole-transporting material may be in a particulate form and in a plate form.

And the plate surface of the hole transport material at the second interface makes a surface contact with the crystal plane of the perovskite compound.

And 80% to 90% of the hole transferring material contained in the hole transporting layer may have a plate surface parallel to the second interface.

According to the present invention, a perovskite solar cell which is excellent in heat resistance and durability and applicable to automobiles can be obtained.

According to the present invention, a perovskite solar cell having a high photoelectric conversion efficiency and improved interfacial adhesion between the hole transport layer and the light absorption layer can be obtained.

The effects of the present invention are not limited to the effects mentioned above. It should be understood that the effects of the present invention include all reasonably possible effects in the following description.

1 is a cross-sectional view of a perovskite solar cell according to the present invention.
2 is an SEM (Scanning Electron Microscope) image of the surface of the light absorbing layer formed in the embodiment of the present invention.
3 (a) is an SEM image of a cross section of a light absorbing layer (Perovskite) and a hole transporting layer (CuPC) formed in an embodiment of the present invention. Fig. 3 (b) is an enlarged view of Fig. 3 (a).
4A and 4B are cross-sectional views of a light absorbing layer and a hole transporting layer of a perovskite solar cell according to an embodiment of the present invention.
FIG. 5 illustrates an interface between a light absorption layer and a hole transport layer of a perovskite solar cell according to an embodiment of the present invention.
6 (a) and 6 (b) are results of thermal cycle performance evaluation of the perovskite solar cell according to the embodiment of the present invention.
FIG. 7 (a) is a result of measuring the photoelectric conversion efficiency of a perovskite solar cell according to an embodiment of the present invention after performing a thermal cycle test.
FIG. 7 (b) is a result of a thermal cycle test of a perovskite solar cell using PTAA as a hole transport material, and then measuring the photoelectric conversion efficiency thereof.
8 is an SEM image of the surface of the light absorbing layer formed in the comparative example.
9 is a result of analyzing the interface between the light absorbing layer and the hole transporting layer of the perovskite solar cell according to the comparative example.
10 shows the results of measurement of the efficiency of a perovskite solar cell according to Examples and Comparative Examples.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features, and advantages of the present invention will become more readily apparent from the following description of preferred embodiments with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described herein but may be embodied in other forms. Rather, the embodiments disclosed herein are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art.

Like reference numerals are used for like elements in describing each drawing. In the accompanying drawings, the dimensions of the structures are shown enlarged from the actual for the sake of clarity of the present invention. The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component. The singular expressions include plural expressions unless the context clearly dictates otherwise.

In this specification, the terms "comprises" or "having" and the like refer to the presence of stated features, integers, steps, operations, elements, components, or combinations thereof, But do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof. Also, where a portion such as a layer, film, region, plate, or the like is referred to as being "on" another portion, this includes not only the case where it is "directly on" another portion, but also the case where there is another portion in between. On the contrary, when a part such as a layer, film, region, plate or the like is referred to as being "under" another part, it includes not only the case where it is "directly underneath" another part but also another part in the middle.

Unless otherwise specified, all numbers, values, and / or representations that express the amounts of components, reaction conditions, polymer compositions, and combinations used herein are intended to include those numbers It should be understood that in all cases the term "about" is to be construed as an approximation reflecting the various uncertainties of the measurement. Also, where a numerical range is disclosed in this specification, such a range is contiguous and includes all values from the minimum value of this range to the maximum value including the maximum value, unless otherwise indicated. Further, when such a range refers to an integer, all integers including the minimum value to the maximum value including the maximum value are included unless otherwise indicated.

In the present specification, when a range is described for a variable, it will be understood that the variable includes all values within the stated range including the end points described in the range. For example, a range of "5 to 10" may include any subrange, such as 6 to 10, 7 to 10, 6 to 9, 7 to 9, etc., as well as values of 5, 6, 7, 8, 9, And will also be understood to include any value between integers that are reasonable within the scope of the stated ranges such as 5.5, 6.5, 7.5, 5.5 to 8.5 and 6.5 to 9, and so on. Also, for example, a range of "10% to 30%" may range from 10% to 15%, 12% to 12%, as well as all integers including values of 10%, 11%, 12%, 13% And any arbitrary integer within the range of ranges described, such as 10.5%, 15.5%, 25.5%, and the like, including any subranges such as 18%, 20%

1 is a cross-sectional view of a perovskite solar cell according to the present invention. Referring to FIG. 1, the perovskite solar cell includes a support substrate 10, a first electrode 20 formed on the support substrate, an electron transport layer 30 formed on the first electrode, A hole transporting layer 50 formed on the light absorbing layer and containing a hole transporting material, and a second electrode 60 formed on the hole transporting layer. The light absorbing layer 40 includes a perovskite compound, .

An object of the present invention is to provide a hole transport layer (50) including a hole transport material having excellent heat resistance and durability.

It is another object of the present invention to provide a perovskite solar cell having improved photoelectric conversion efficiency and interfacial adhesion by improving the characteristics of the interface (A) formed between the light absorption layer (40) and the hole transport layer (50) .

Hereinafter, the structure of the perovskite solar cell will be described in detail.

The support substrate 10 may be made of a transparent material such as glass or transparent plastic. However, the present invention is not limited thereto, and when light is not received by the support substrate 10, an opaque material such as metal such as stainless steel or opaque plastic may be used.

The first electrode 20 may be a transparent conductive electrode for improving light transmission. For example, a fluorine-containing tin oxide (FTO), indium doped tin oxide (ITO), zinc oxide (ZnO), or the like.

The electron transport layer 30 may be formed in any configuration and shape as long as electrons can move smoothly, but it may be formed of a porous layer made of metal oxide particles such as titanium dioxide (TiO ₂ ).

The light absorption layer 40 includes a perovskite compound having a cubic crystal structure. Here, the 'perovskite compound' means a compound having a perovskite structure, and may be represented by the following formula (1).

[Chemical Formula 1]

ABX ₃

Here, A is selected from the group consisting of Formamidinium (FA), Methylammonium (MA), and combinations thereof, and B is selected from the group consisting of lead (Pb), tin (Sn) And X is selected from the group consisting of chlorine (Cl), bromine (Br), iodine (I), and combinations thereof.

The perovskite compound may be selected from the group consisting of, for example, FAPbI ₃ , MAPbI _3, and combinations thereof.

In the present invention, the crystal plane of the perovskite compound having a cubic crystal structure at the interface (A) between the light absorbing layer (40) and the hole transporting layer (50) is developed at an orientation angle within a specific range, And the interface adhesion force is improved.

For this, the orientation angle of the crystal plane of the perovskite compound with respect to the surface of the support substrate 10 at the interface (A) is preferably 20 ° to 60 °. In detail, it is preferable that the orientation angle is 20 ° to 30 ° or 50 ° to 60 °. Here, the 'orientation angle' refers to the angle between the imaginary plane extending from the surface of the support substrate 10 or from it and the imaginary crystal plane extending from the crystal plane of the perovskite compound formed at the interface A, .

The interface at which the orientation angle of the crystal plane of the perovskite compound with respect to the surface of the support substrate 10 at the interface (A) is 20 to 30 is referred to as a first interface, and the interface at which the orientation angle is 50 to 60 The interface is referred to as the second interface. That is, the interface (A) includes a first interface and a second interface. The first interface and the second interface need not necessarily be consecutive in appearance, and the arrangement may be random.

This will be described later along with the hole transporting material of the hole transporting layer 50.

The hole transport layer 50 includes a hole transport material, which is a compound having a unit structure represented by the following formula (2).

(2)

ML

Here, M is a metal selected from the group consisting of copper (Cu), zinc (Zn), iron (Fe), magnesium (Mg), cobalt (Co), nickel (Ni) Is a phthalocyanine-based ligand compound which is coordinatively bonded to a metal (M) ion.

Specifically, the hole transport material may be a compound having a unit structure represented by the following formula (3).

(3)

Wherein M may be selected from the group consisting of copper (Cu), zinc (Zn), iron (Fe), magnesium (Mg), cobalt (Co), nickel (Ni) the or may be a unsubstituted C _{1 -20} alkyl.

The hole transporting material may be a particulate material having a unit structure represented by Chemical Formula 2 or 3, and the particulate material may be in the form of a plate.

When the hole transfer material is applied to the interface (A) where the perovskite compound is arranged at a specific orientation angle as described above, the hole transfer material has a plate-like shape, . Therefore, by adjusting the orientation angle of the perovskite compound at the interface (A), the plate surface of the hole transport material can be in surface contact with the crystal plane of the perovskite compound, thereby improving the photoelectric conversion efficiency . Since the contact area is widened as compared with the case where the edge (plate-like rim) of the hole transport material is in line contact with the crystal plane of the perovskite compound, the hole transport is advantageous and the photoelectric conversion efficiency is improved do.

This will be described later in more detail.

The second electrode 60 may be a counter electrode of the first electrode 20, as long as it is commonly used in the field of solar cells. For example, it may be selected from the group consisting of gold, silver, platinum, palladium, copper, aluminum, carbon, cobalt sulfide, copper sulfide, nickel oxide and combinations thereof.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

Example

Perovskite  Manufacture of solar cells

A perovskite solar cell having the structure shown in FIG. 1 was manufactured.

A light absorption layer was formed to specifically in the laminate of the support substrate _{/ FTO / TiO 2 (FAPbI 3} ) 0.85 (MAPbBr 3) 0. 15 Fe lobe, which is represented by the Sky agent compound. At this time, the perovskite compound precursor solution was spin-coated so that the crystal face of the perovskite compound 100 at the outermost surface of the light absorption layer had an orientation angle of 20 ° to 60 °. 2 is a scanning electron microscope (SEM) image of the surface of the light absorbing layer.

A compound having a unit structure represented by Formula 3 (hereinafter, referred to as 'CuPC') was applied to the light absorption layer by a solution casting process to form a hole transport layer. 3 (a) is an SEM image of the cross section of the light absorption layer (Perovskite) and the hole transport layer (CuPC). Fig. 3 (b) is an enlarged view of Fig. 3 (a).

A gold (Au) thin film as a second electrode was provided on the hole transport layer to complete a perovskite solar cell.

Interfacial Analysis

The orientation angle of the crystal plane of the perovskite compound at the interface (A) between the light absorbing layer (40) and the hole transporting layer (50) and the arrangement of the hole transporting material according to the GIWAXS (Glazing-incidence wide-angle X- ).

Specifically, an X-ray beam was irradiated onto the perovskite solar cell having a support substrate / FTO / TiO ₂ / (FAPbI ₃ ) _0.85 (MAPbBr ₃ ) _0.15 / CuPC structure at an incident angle of 0.15 ° to form a hole transport layer (CuPC) And a crystal structure of a perovskite compound of a light absorption layer having a thickness of 4 nm (i.e., near the interface (A)) were analyzed. The results are shown in Figs. 4 (a) and 4 (b).

Corresponds to FIG. 4 (a) In the perovskite Scattering peak due to crystals of the compound agent are strip semicircular shape shown in the _xy q = ^-1 1.0Å and 2.0Å ^-1. The intensity of the signal according to the angle of the semicircle appearing at q _xy = 1.0? ^-1 is shown in a graph as shown in FIG. 4 (b). At χ = 22 ° and 55 °, the intensity of the signal is large and symmetrical at 125 ° and 155 °. Because the perovskite compound is a cubic crystal structure, it appears symmetrical. From this result, it can be seen that the (100) crystal face of the perovskite compound has an orientation angle of 20 ° to 30 ° (first interface) and 50 ° to 60 ° (second interface) with respect to the support substrate.

In FIG. 4 (a), the scattering peak due to the hole transport material corresponds to a semi-circular band at q _xy = 0.37 Å ^-1 . The scattering at q _xy = 0.37 Å ^-1 is observed when the intermolecular distance is 20 Å to 21 Å, which is due to the fact that the plane of the hole transporting material molecule of Fig. 4 (a) is shifted by 27.5-32.4 °, phase, which is the first phase of the reaction. The signal measured at q _xy = 0.37 Å ^-1 is strongest at χ = 90 ° and is weak at χ = 29 ° and χ = 151 °. This means that 80% to 90% of the hole-transporting material is arranged in parallel with the interface (A) of the supporting substrate with the crystal plane in which the plate surfaces are laminated. Here, '%' of the hole-transporting material means [particle size of the hole-transporting material in the plane of the plate surface / particle image of the total hole-transporting material contained in the hole transporting layer X 100].

The interface (A) is shown in FIG. 5 based on the results of FIGS. 4 (a) and 4 (b). (A ') at an orientation angle of the crystal plane of the perovskite compound with respect to the surface of the support substrate is 20 ° to 30 °, and the orientation angle is 50 ° to 60 ° (A "). ≪ / RTI > Further, the hole transport material (one particle phase of the hole transport material, B) in the vicinity of the second interface (A '') is in surface contact with the crystal plane of the perovskite compound. In addition, most of the hole transporting material (80% to 90%) of the hole transporting material is arranged in parallel with the crystal plane of the perovskite compound constituting the second interface (A ''). In the case of having such an interfacial structure, hole transport at the interface (A) is facilitated and the interfacial adhesion force is greatly improved, so that the photoelectric conversion efficiency and safety of the perovskite solar cell are greatly improved.

Heat cycle  Performance evaluation

Thermal cycle performance was evaluated by repeatedly heating and cooling the perovskite solar cell from -40 ° C to 110 ° C. Here, 'thermal cycle performance' means stability when repeatedly exposed to low temperature and high temperature and durability against fatigue failure of the device under thermomechanical stress. The results are shown in Figs. 6 (a) and 6 (b).

Referring to FIGS. 6 (a) and 6 (b), current density-voltage curves of the solar cell under the artificial sun of 100 mW / cm ² intensity and the AM 1.5G standard spectrum before and after the heat cycle test were compared. ~ 85 ℃ After 50 cycles of the heat cycle test, there is no change in the voltage-current density curve measured at OV to open-circuit voltage (Forward sweep) and at open-circuit voltage to 0V (reverse seep) The open-circuit voltage is increased after 3 times in the temperature interval. Therefore, the perovskite solar cell is thermally and mechanically stable. The results of the photoelectric conversion efficiency calculated from the current density-voltage curves measured before and after the thermal cycle test from several of the above-mentioned perovskite solar cell elements are shown in FIG. 7 (a).

In addition, the same experiment was carried out for a solar cell using PTAA as a hole transport material, and the photoelectric conversion efficiency thereof was measured. The result is shown in Fig. 7 (b).

Referring to FIGS. 7 (a) and 7 (b), it can be seen that the perovskite solar cell according to the present invention has a significantly smaller drop in photoelectric conversion efficiency than PTAA.

Comparative Example

Perovskite  Manufacture of solar cells

A light absorbing layer was formed by varying the composition of the perovskite precursor solution and the coating process conditions. 8 is an SEM image of the surface of the light absorbing layer. A perovskite solar cell was manufactured in the same manner as in Example except for this.

Interfacial Analysis

The orientation angle of the crystal plane of the perovskite compound at the interface between the light absorbing layer and the hole transporting layer and the arrangement of the hole transporting material accordingly were analyzed by GIWAXS. The results are shown in Fig.

In Figure 9, the q _xy = 1.0Å ^-1 and semicircular shape of the strip shown in 2.0Å ^-1 inde Scattering peak due to crystals of the Fe lobe Sky agent compound, χ = 90 ° close to the strength of the signal that appears on the zoom bar, which (100) crystal face of the perovskite compound is formed with an orientation angle of about 90 degrees with respect to the support substrate. In this case, the hole transport material can not make a surface contact with the crystal plane of the perovskite compound, which is disadvantageous for hole transport.

Measurement of solar cell efficiency

The efficiency of the perovskite solar cells of the Examples and Comparative Examples was measured by an experimental method for measuring the current density-voltage curve of the solar cell under the artificial sun of AM 1.5G standard spectrum and intensity of 100mW / cm ² . The results are shown in Fig.

As a result, the short-circuit current density and the open-circuit voltage were both measured to be decreased. As a result, the holes generated in the perovskite-type light absorbing layer manufactured in the comparative example are disadvantageous to transfer to the hole- It can be seen that the perovskite solar cell according to the example is more efficient.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the scope of the present invention is not limited to the disclosed exemplary embodiments. Various modifications and improvements of those skilled in the art are also within the scope of the present invention.

10: support substrate 20: first electrode 30: electron transport layer
40: light absorbing layer 50: hole transporting layer 60: second electrode
A: Interface between the light absorption layer and the hole transporting layer

Claims (6)

A support substrate;
A first electrode formed on the supporting substrate;
An electron transport layer formed on the first electrode;
A light absorbing layer formed on the electron transporting layer and including a perovskite compound having a cubic crystal structure;
A hole transport layer formed on the light absorption layer and including a hole transport material; And
And a second electrode formed on the hole transport layer,
An interface is formed between the light absorption layer and the hole transport layer,
Wherein the interface has a first interface at an orientation angle of the crystal plane of the perovskite compound with respect to the surface of the support substrate of 20 to 30 degrees; And a second interface having an orientation angle of the crystal plane of the perovskite compound with respect to the surface of the support substrate of 50 ° to 60 °. The method according to claim 1,
Wherein the perovskite compound is represented by the following formula (1).
[Chemical Formula 1]
ABX ₃
Here, A is selected from the group consisting of Formamidinium (FA), Methylammonium (MA) and combinations thereof,
B is selected from the group consisting of lead (Pb), tin (Sn), and combinations thereof,
X is selected from the group consisting of chlorine (Cl), bromine (Br), iodine (I), and combinations thereof. The method according to claim 1,
Wherein the hole transport material is a compound having a unit structure represented by the following formula (2).
(2)
ML
Here, M is a metal selected from the group consisting of copper (Cu), zinc (Zn), iron (Fe), magnesium (Mg), cobalt (Co), nickel (Ni) Is a phthalocyanine-based ligand compound which is coordinatively bonded to a metal (M) ion. The method according to claim 1,
Wherein the hole transport material is a compound having a unit structure represented by the following formula (3).
(3)

Wherein M is selected from the group consisting of copper (Cu), zinc (Zn), iron (Fe), magnesium (Mg), cobalt (Co), nickel (Ni) Unsubstituted C _{1 -20} alkyl group. The method according to claim 3 or 4,
Wherein the hole transporting material is in the form of a particle, and is in the form of a platelike, perovskite solar cell. 6. The method of claim 5,
Wherein the plate interface of the hole transport material at the second interface makes a surface contact with the crystal plane of the perovskite compound.

Images