KR20160015723A - Electron carrier for solar cell and method of fabricating thereof - Google Patents

Abstract

The present invention relates to an electron carrier for a solar cell for improving stability in a solar cell and a manufacturing method thereof. Especially, the present invention provides the electron carrier of which stability is improved in a perovskite solar cell which is actively researched recently as a high efficiency solar cell. The present invention coats an oxide semiconductor with high deliquescence on an existing nano-particle based electron carrier surface to manufacture a stable electron carrier which absorbs moisture. The stable electron carrier is applied to the perovskite solar cell to overcome a problem that an existing perovskite solar cell is weak against moisture, thereby obtaining long-term stability.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron carrier for a solar cell,

The present invention relates to an electron carrier having improved stability in a solar cell and a method for producing the same. In particular, the present invention can provide an electron carrier having improved stability in a perovskite solar cell that has been actively studied as a high efficiency solar cell in recent years.

Research on renewable and clean alternative energy sources such as solar energy, wind power, and hydro power is actively being conducted to solve the global environmental problems caused by depletion of fossil energy and its use.

Among these, there is a great interest in solar cells that change electric energy directly from sunlight. Here, a solar cell refers to a cell that generates a current-voltage by utilizing a photovoltaic effect that absorbs light energy from sunlight to generate electrons and holes.

Currently, np diode-type silicon (Si) single crystal based solar cells with a light energy conversion efficiency of more than 20% can be manufactured and used for actual solar power generation. Compound semiconductors such as gallium arsenide (GaAs) There is also solar cell using. However, since inorganic semiconductor-based solar cells require highly refined materials for high efficiency, a large amount of energy is consumed in the purification of raw materials, and expensive processes are required in the process of making single crystals or thin films using raw materials And the manufacturing cost of the solar cell can not be lowered, which has been a hindrance to a large-scale utilization.

Accordingly, in order to manufacture a solar cell at a low cost, it is necessary to drastically reduce the cost of the material or manufacturing process used as a core of the solar cell. As an alternative to the inorganic semiconductor-based solar cell, Type solar cells and organic solar cells have been actively studied.

In recent years, silicon-based, organic dye-based, and new perovskite-based solar cells are in the process of developing solar cells. Currently, perovskite-based solar cells are emerging as the most promising solar technologies. The highest efficiency of the perovskite solar cell reported to date is 15%, which is expected to be further improved.

Since perovskite has a special crystal structure such as calcium titanium dioxide, perovskite solar cells are attractive, and this structure enables high charge transport mobility and long diffusion distance in the solar cell, This allows long distance travel without loss, and as a result, electrons and holes can pass through thicker solar cells, absorbing more light.

The CH ₃ NH ₃ PbI ₃ perovskite light absorber used as a light absorbing and activating material of the perovskite solar cell has a high possibility of developing an ultra-low-cost low-cost solar cell based on the high extinction coefficient characteristic. However, the perovskite optical absorber is decomposed into moisture as compared with the excellent optical characteristics and has low stability, which limits the commercialization of the solar cell. Therefore, overcoming this stability problem becomes a very important issue.

In the perovskite solar cell, the perovskite light absorber exhibits low stability to moisture, and in order to overcome this, the present invention is applied to an existing perovskite solar cell, And to provide long-term stable solar cell characteristics by dramatically overcoming the low stability of the absorber.

The present invention relates to a stabilized electron carrier that absorbs moisture by applying an oxide semiconductor having high susceptibility to the surface of an existing nanoparticle-based electron transporting material, and applies it to a perovskite solar cell, The objective is to overcome the problem and ensure long-term stability.

An electron carrier for a solar cell according to an embodiment of the present invention includes: an electron transport nanoparticle thin film layer; And a metal oxide coated on the surface of the electron transport nanoparticle thin film layer.

The metal oxide is preferably a material having high deterioration and is preferably a material having high decomposability such as MgO, CaO, Al ₂ O ₃ , Fe ₂ O ₃ , NiO, Cobalt (CoO), and lanthanum oxide (La ₂ O ₃ ).

The coating thickness of the metal oxide is preferably more than 0 nm and 10 nm or less.

A method of manufacturing an electron carrier for a solar cell according to an embodiment of the present invention includes: preparing an electron transport nanoparticle thin film layer; Preparing a solution containing a metal salt which is a source of the metal oxide; Applying a solution containing the metal salt to the electron transport nanoparticle thin film layer; Hydrating the metal salt to coat the surface of the electron transport nanoparticle thin film layer with a hydrate; And forming a metal oxide coating layer from the hydrate coated on the surface of the electron transport nanoparticle thin film layer.

The metal salt is preferably at least one selected from the group consisting of a carbonate, a sulfate, an ammonium salt, a nitrate salt, an organic acid salt, a cloide, and an alkoxide.

The hydrates are magnesium hydroxide (Mg (OH) _2), calcium hydroxide (Ca (OH) _2), aluminum hydroxide (Al (OH) _3), iron hydroxide (FeOOH), nickel hydroxide (Ni (OH _2)), cobalt hydroxide ( Co (OH) ₂ ), and lanthanum hydroxide (La (OH) ₃ ).

The metal oxide is magnesium oxide (MgO), calcium (CaO), aluminum oxide (Al ₂ O _3), iron oxide (Fe ₂ O _3), nickel oxide (NiO), cobalt oxide (CoO) and lanthanum oxide (La ₂ O < ₃ >).

The coating thickness of the metal oxide is preferably more than 0 nm and 10 nm or less.

The step of applying the solution containing the metal salt to the electron transport nanoparticle thin film layer is preferably performed using spin coating.

According to the present invention, by forming an oxide semiconductor layer excellent in porosity and deliquescence on an existing nanoparticle-based electron carrier, water can be absorbed from a moisture-sensitive light absorption layer to prevent decomposition of the perovskite light absorption layer, There is an effect to improve.

1 is a schematic diagram of a solar cell including an electron carrier for a solar cell having improved stability according to an embodiment of the present invention.
2 shows a flow chart of a method for manufacturing an electron carrier for a solar cell with improved stability according to an embodiment of the present invention.
FIG. 3 shows a transmission electron microscope image of TiO ₂ nanoparticles coated with MgO.
FIG. 4 shows evaluation of solar cell characteristics in which TiO ₂ nanoparticles are coated with MgO and comparative solar cell characteristics.
5 shows the evaluation of the optical properties of the perovskite-coated embodiment and the comparative example after coating the TiO ₂ nanoparticles with MgO.
Various embodiments are now described with reference to the drawings, wherein like reference numerals are used throughout the drawings to refer to like elements. For purposes of explanation, various descriptions are set forth herein to provide an understanding of the present invention. It is evident, however, that such embodiments may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form in order to facilitate describing the embodiments.

The following description provides a simplified description of one or more embodiments in order to provide a basic understanding of embodiments of the invention. This section is not a comprehensive overview of all possible embodiments and is not intended to identify key elements or to cover the scope of all embodiments of all elements. Its sole purpose is to present the concept of one or more embodiments in a simplified form as a prelude to the more detailed description that is presented later.

The present invention relates to a stabilized electron carrier that absorbs moisture by applying an oxide semiconductor having high susceptibility to the surface of an existing nanoparticle-based electron transporting material, and applies it to a perovskite solar cell, It is content to overcome the problem and to guarantee long-term stability.

In order to achieve the problem of being vulnerable to moisture, an attempt is made to provide an electron carrier for a solar cell having improved stability.

An electron carrier for a solar cell having improved stability according to an embodiment of the present invention includes: an electron transporting nanoparticle thin film layer; And a metal oxide coated on the surface of the electron transporting nanoparticle thin film layer.

1 is a schematic diagram of a solar cell including an electron carrier for a solar cell having improved stability according to an embodiment of the present invention.

As shown in FIG. 1, there is an electron transporting nanoparticle thin film layer, and a metal oxide layer is coated on the surface of the thin film layer to prevent moisture penetration. Thus, the perovskite light absorber maintains excellent optical characteristics and low stability .

In this case, the metal oxide must be a highly corrosive substance. Here, high deliberateness means that higher deliberateness means better, and is not intended to limit the numerical value in particular. This is because a metal oxide having high deliquescence can be coated on the surface of the electron transport nanoparticle thin film layer to absorb moisture, thereby solving the problem of moisture of the perovskite solar cell.

Deliquescent a high metal oxide magnesium (MgO), calcium (CaO), alumina oxide (Al ₂ O _3), iron oxide (Fe ₂ O _3), nickel oxide (NiO), cobalt oxide (CoO) and lanthanum oxide ( La ₂ O ₃ ). All of the metal oxides listed above are highly deliquescent and can be coated on the surface of the electron transport nanoparticle thin film layer to absorb moisture sufficiently.

On the other hand, the thickness of the metal oxide layer having high deliquescence is an important point. This is because magnesium oxide (MgO) is a material having a large band gap, and therefore it is difficult to inject electrons. Therefore, if the thickness of the MgO is large, it is difficult to transfer electrons, which may lower the efficiency of the solar cell .

Therefore, the thickness is also an important point, and the thickness of the metal oxide layer having high deliquescence is preferably as thin as possible, and preferably has a thickness of more than 0 nm and less than 10 nm. In the case of having a thickness of 10 nm or less, a tunneling effect is generated so that electrons can be injected. Even if a metal oxide coating layer is present, the efficiency of the perovskite solar cell is maintained, . When the thickness is more than 10 nm, there is a problem that the tunneling effect is hardly generated, so it is important to limit the thickness.

2 shows a flow chart of a method for manufacturing an electron carrier for a solar cell with improved stability according to an embodiment of the present invention.

Referring to FIG. 2, a method of fabricating an improved electron transport material for a solar cell according to an embodiment of the present invention includes: preparing (S 210) an electron transport nanoparticle thin film layer; Preparing a solution containing a metal salt which is a source of the metal oxide (S 220); (S 230) applying a solution containing a metal salt to the electron transport nanoparticle thin film layer; (S 240) coating the surface of the electron transport nanoparticle thin film layer with a hydrate to hydrate the metal salt; And forming a metal oxide coating layer from the hydrate coated on the surface of the electron transport nanoparticle thin film layer (S 250).

In step S 210, the electron transport nanoparticle thin layer is formed by forming a thin TiO ₂ thin film having a thickness of 20 to 100 nm on the transparent electrode, spin coating a spherical TiO ₂ nanoparticle paste having a size of about 20 nm, Prepare by post heat treatment. As shown in FIG. 1, the electron transporting nanoparticles may be formed on the hole blocking layer. The electron transporting nanoparticles are generally made of TiO ₂ or ZnO.

In step S 220, a solution containing a metal salt, which is a source of the metal oxide to be coated on the electron transport nanoparticle thin film layer, is prepared.

In this case, the metal salt may include at least one selected from the group including carbonates, sulfates, ammonium salts, nitrates, organic acid salts, cloides, and alkoxides.

In step S 230, the solution containing the metal salt is applied according to the concentration of the metal salt. Preferably, the solution containing more than 0 wt% and less than 5 wt% of the solution should be applied. When the concentration of the metal salt is 5 wt% or more, the thickness of the metal oxide to be coated becomes too thick and electrons are not easily transferred. Thereafter, a spin coating process is performed on the electron transport nanoparticle thin film layer, and then, in step S 240, the metal salt is hydrated at a temperature of less than 550 ° C. to hydrate the surface of the electron transport nanoparticle thin layer.

The step of applying the solution containing the metal salt to the electron transporting nanoparticle thin film layer in step S 230 is preferably performed using spin coating.

Hydroxide is magnesium hydroxide (Mg (OH) _2), calcium hydroxide (Ca (OH) _2), aluminum hydroxide (Al (OH) _3), iron hydroxide (FeOOH), nickel hydroxide (Ni (OH _2)), cobalt hydroxide (Co (OH) ₂ ), and lanthanum hydroxide (La (OH) ₃ ).

Finally, in step S 250, a metal oxide coating layer is formed from the hydrate coated on the surface of the electron transporting nanoparticle thin film layer. In step S 250, a metal oxide layer is obtained from the hydrate through heat treatment, and the heat treatment temperature is usually performed at a temperature of about 300 ° C to 500 ° C, preferably 400 ° C.

The metal oxide is magnesium (MgO), calcium oxide (CaO), aluminum oxide (Al ₂ O _3), iron oxide (Fe ₂ O _3), nickel oxide (NiO), cobalt oxide (CoO) and lanthanum oxide (La ₂ O ₃ ), and it is preferable that the thickness is 1 nm to 10 nm. Since this is the part described above, redundant description will be omitted.

Hereinafter, the contents of the present invention will be further described with reference to specific embodiments.

≪ Example 1 >

10 cc of magnesium methoxide dissolved in methanol in an amount of 6 wt% is mixed with 6 cc of methanol and stirred for about 10 minutes. 1 cc of the mixed solution is diluted in 10 cc of methanol and stirred for about 10 minutes. The solution mixed with the two solutions is sprayed on the TiO ₂ thin film and coated with spin coating at 2500 rpm for 20 seconds once to form a magnesium hydroxide film on the TiO ₂ .

3 is a transmission electron micrograph of a magnesium oxide oxide layer obtained by heat-treating the obtained magnesium hydroxide at 400 ° C. As can be seen from the transmission microscope photograph, TiO ₂ nanoparticles of 20 nm size are uniformly coated with a porous magnesium oxide layer of 3 nm thickness.

≪ Example 2 >

1, a transparent conductive layer was formed on the substrate, a dense TiO ₂ hole blocking layer was formed on the transparent conductive layer formed, and a TiO ₂ electron transporting nanoparticle layer was spin-coated on the hole blocking layer to form 200 nm do. A magnesium oxide layer mixed by the method of Example 1 is formed on the electron transfer nanoparticle layer to prepare an electron carrier having a metal oxide -TiO ₂ double structure. The substrate on which the electron carrier is formed is immersed in PbI ₂ solution dissolved in dimethylformamide, and is then immersed in CH ₃ NH ₃ I solution dissolved in 2-propanol to crystallize to form a perovskite light absorbing layer. A gold electrode was formed on top of the formed light absorbing layer by using thermal evaporation method, and a solar cell device was fabricated and measured. 4 is an IV graph of a solar cell device manufactured according to an embodiment of the present invention, and it can be seen that the same efficiency is exhibited irrespective of the presence or absence of a metal oxide having high deliquescence.

≪ Example 3 >

In order to measure the long-term stability of the solar cell device fabricated according to one embodiment of the present invention, the stability of the optical absorber with respect to time was measured. The result is shown in FIG. The perovskite optical absorber coated on the MgO-TiO ₂ structure showed superior stability characteristics after 15 days since the optical absorptivity was not significantly lowered than that of the perovskite optical absorber coated on the existing TiO ₂ nanoparticle structure have. The change of light absorption with time indicates that water reacts with perovskite in the atmosphere and decomposes, and it is confirmed that MgO - coated cells do not change much.

The description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features presented herein.

Claims (10)

Electron transport nanoparticle thin film layer; And
And a metal oxide coated on the surface of the electron transporting nanoparticle thin film layer.
Electronic carrier for solar cells.
The method according to claim 1,
Characterized in that the metal oxide is a substance having high deliquescence.
Electronic carrier for solar cells.
3. The method of claim 2,
The metal oxide is magnesium oxide (MgO), calcium (CaO), aluminum oxide (Al ₂ O _3), iron oxide (Fe ₂ O _3), nickel oxide (NiO), cobalt oxide (CoO) and lanthanum oxide (La ₂ O < ₃ >).
Electronic carrier for solar cells.
The method according to claim 1,
Wherein the coating thickness of the metal oxide is greater than 0 nm and less than or equal to 10 nm.
Electronic carrier for solar cells.
Preparing an electron transport nanoparticle thin film layer;
Preparing a solution containing a metal salt which is a source of the metal oxide;
Applying a solution containing the metal salt to the electron transport nanoparticle thin film layer;
Hydrating the metal salt to coat the surface of the electron transport nanoparticle thin film layer with a hydrate; And
And forming a metal oxide coating layer from the hydrate coated on the surface of the electron transport nanoparticle thin film layer.
A method for manufacturing an electron carrier for solar cells.
6. The method of claim 5,
Wherein the metal salt is at least one selected from the group consisting of a carbonate, a sulfate, an ammonium salt, a nitrate salt, an organic acid salt, a cloide, and an alkoxide.
A method for manufacturing an electron carrier for solar cells.
6. The method of claim 5,
The hydrates are magnesium hydroxide (Mg (OH) _2), calcium hydroxide (Ca (OH) _2), aluminum hydroxide (Al (OH) _3), iron hydroxide (FeOOH), nickel hydroxide (Ni (OH _2)), cobalt hydroxide ( Co (OH) ₂ ), and lanthanum hydroxide (La (OH) ₃ ).
A method for manufacturing an electron carrier for solar cells.
6. The method of claim 5,
The metal oxide is magnesium oxide (MgO), calcium (CaO), aluminum oxide (Al ₂ O _3), iron oxide (Fe ₂ O _3), nickel oxide (NiO), cobalt oxide (CoO) and lanthanum oxide (La ₂ O < ₃ >).
A method for manufacturing an electron carrier for solar cells.
6. The method of claim 5,
Wherein the coating thickness of the metal oxide is greater than 0 nm and less than or equal to 10 nm.
A method for manufacturing an electron carrier for solar cells.
6. The method of claim 5,
Wherein the step of applying the solution containing the metal salt to the electron transport nanoparticle thin film layer is performed using spin coating.
A method for manufacturing an electron carrier for solar cells.

Images