WO2018124390A1 - Perovskite solar cell using graphene electrode, and manufacturing method therefor - Google Patents

Abstract

The present invention relates to: a perovskite solar cell using a graphene electrode, capable of work function control while maintaining high electrical conductivity of graphene; and a manufacturing method therefor. A p-type graphene electrode is used in a perovskite solar cell structure and the doping concentration thereof is controlled, and thus energy conversion efficiency of the perovskite solar cell can be increased.

Description

Perovskite Solar Cell Using Graphene Electrode and Manufacturing Method Thereof

The present invention relates to a perovskite solar cell using a graphene electrode and a method for manufacturing the same, and more particularly to a graphene-based perovskite solar cell that can control the work function while maintaining high electrical conductivity of graphene It is about.

The perovskite material is an AMX ₃ structure (A, M is a cation, X is an anion) and is an organic / inorganic composite material having an ionic crystal and a direct band gap. This material has high absorption coefficient, thin film, long charge diffusion distance, and high efficiency of solar cell. In addition, due to the high dielectric constant it exhibits a low exciton binding energy and has a high open voltage characteristic.

The perovskite material has a great potential in terms of practical use because it can be manufactured in a low-cost, high-efficiency optoelectronic device can be a solution process.

Since liquid-sensitized solar cells were first manufactured by Kojima et al., Solid-sensitized perovskite solar cells with 22.1% efficiency have been developed.

The developed perovskite materials have low moisture and heat resistance and therefore require a passivation layer. It can be used as an ultra-thin solar cell and can be used as a next-generation flexible and mobile independent power source. However, in order to realize perovskite-based flexible solar cells, development of flexible electrodes that are flexible is essential. .

For this purpose, development of electrodes having chemical resistance and barrier properties is very important, and graphene electrodes may be very promising candidate electrodes.

Recently, studies on solar cells using graphene electrodes have been reported. However, in the prior art, it was difficult to control the work function of graphene, and the electrical conductivity was also not high, so there was a limit that the characteristics of the solar cells could not be maximized.

In order to overcome these limitations of the prior art, the present invention is expected to be able to manufacture high-efficiency graphene-based perovskite solar cells using a chemical doping method capable of adjusting the work function while maintaining high electrical conductivity of graphene. do.

The present invention is to provide a perovskite solar cell using a graphene transparent electrode whose characteristics are controlled by doping.

In addition, the present invention by using a p-type graphene electrode in the perovskite solar cell structure by adjusting the doping concentration, the perovskite using a graphene electrode that can increase the energy conversion efficiency of the perovskite solar cell To provide a skylight solar cell and a method of manufacturing the same.

 In the perovskite solar cell using a graphene electrode according to an embodiment of the present invention is a graphene electrode formed by applying an impurity solution on the surface of the graphene transferred on the substrate, holes deposited on the doped graphene electrode A transfer layer, a barrier layer formed of a metal oxide of a thin film having a predetermined thickness by coating a perovskite structure material on the hole transfer layer, an electron transfer layer formed on the barrier layer and the electron transfer layer An upper electrode formed on the layer.

The graphene electrode is formed by spin coating a p-type impurity solution on the graphene to dope the graphene transferred on the substrate, and the electrode characteristics are improved in proportion to the doping concentration of the p-type impurity solution. It features.

In addition, the graphene electrode is formed by the p-type impurity solution of gold chloride (Gold chloride, AuCl ₃ ), the doping concentration may be controlled by the amount of powder of the gold chloride.

The p-type impurity solution may be formed of at least one of nitric acid (HNO ₃ ), rhodium chloride (RhCl ₃ ), and trifluoromethanesulfonic acid (TFSA) in addition to the gold chloride.

The graphene is manufactured by chemical vapor deposition (CVD), transferred onto the substrate, and then formed by removing poly (methyl methacrylate) (PMMA).

The hole transport layer may be formed by spin coating a methanol and a PEDOT: PSS solution on the doped graphene electrode and then evaporating the methanol.

The blocking layer may be formed by spin coating the perovskite structure material and dimethylformamide (N, N, dimethylformamide) solution on the hole transport layer.

The electron transport layer may be formed by spin coating a PCBM (Phenyl-C61-butyric acid methyl ester) and toluene solution, which are electron transport layers, on the blocking layer.

The upper electrode may include at least one of silver (Ag), gold (Au), copper (Cu), aluminum (Al), platinum (Pt), and an alloy thereof using a thermal evaporator on the electron transport layer. It can be formed of one material.

In the method of manufacturing a perovskite solar cell using a graphene electrode according to an embodiment of the present invention to transfer the graphene on a substrate, to form a graphene electrode by applying an impurity solution on the surface of the transferred graphene Step, depositing a hole transport layer on the doped graphene electrode, by applying a material of the perovskite structure on the hole transport layer to form a barrier layer of a metal oxide of a thin film of a predetermined thickness Forming an electron transport layer on the blocking layer and forming an upper electrode on the electron transport layer.

The forming of the graphene electrode may include spin coating a p-type impurity solution on the graphene to form the graphene electrode to dope the graphene transferred on the substrate, and a doping concentration of the p-type impurity solution. It may be characterized in that to improve the electrode characteristics of the graphene electrode in proportion to.

The graphene electrode is formed by the p-type impurity solution, which is gold chloride (AuCl ₃ ), and the doping concentration may be controlled by the amount of powder of the gold chloride.

In the depositing of the hole transport layer, after spin-coating methanol and PEDOT: PSS solution on the doped graphene electrode, the hole transport layer may be deposited by evaporating the methanol.

The forming of the blocking layer may include spin-coating the perovskite structure material and dimethylformamide (N, N, dimethylformamide) solution on the hole transport layer to form the blocking layer of perovskite structure material. Can be formed.

In the forming of the electron transport layer, the electron transport layer, which is an electron transfer layer, may be formed by spin coating a PCBM (Phenyl-C61-butyric acid methyl ester) and toluene solution on the blocking layer.

The forming of the upper electrode may include silver (Ag), gold (Au), copper (Cu), aluminum (Al), platinum (Pt), and these using a thermal evaporator on the electron transport layer. The upper electrode may be formed of at least one material of an alloy.

According to an embodiment of the present invention, it is possible to provide a perovskite solar cell using a graphene transparent electrode whose characteristics are controlled by doping.

In addition, according to the embodiment of the present invention, by controlling the doping concentration by using a p-type graphene electrode in the perovskite solar cell structure, it is possible to increase the energy conversion efficiency of the perovskite solar cell.

1 illustrates a structure example of a perovskite solar cell using a graphene electrode according to an embodiment of the present invention.

2 illustrates an example of transferring graphene onto a substrate according to an embodiment of the present invention.

3A and 3B illustrate an example of manufacturing doped graphene according to an embodiment of the present invention.

Figure 4 shows the experimental results for the doping degree of gold chloride according to an embodiment of the present invention.

5a to 5g show the results of experiments on the surface roughness and the formation of nanoparticles at different doping concentrations according to an embodiment of the present invention.

Figure 6 shows the experimental results for the graphene sheet resistance at different doping concentrations according to an embodiment of the present invention.

Figure 7 shows the experimental results for the permeability of graphene at different doping concentrations according to an embodiment of the present invention.

8 shows experimental results of the characteristics of the DC conductivity and the optical conductivity at different doping concentrations according to the embodiment of the present invention.

Figure 9 shows the experimental results for the work function at different doping concentrations according to an embodiment of the present invention.

10A and 10B illustrate experimental results of graphene field effect transistors at different doping concentrations according to an exemplary embodiment of the present invention.

FIG. 11 illustrates a scanning electron microscope image of a perovskite solar cell using a graphene electrode according to an embodiment of the present invention.

12A and 12B illustrate evaluation results of characteristics of a perovskite solar cell using a graphene electrode according to an exemplary embodiment of the present invention.

Figure 13 shows the experimental results for the external quantum efficiency of the perovskite solar cell using a graphene electrode according to an embodiment of the present invention.

14A and 14B illustrate graphs of measurement results of diffusion coefficients and carrier decay times at different doping concentrations and calculation examples of diffusion distances according to embodiments of the present invention.

15A to 15F illustrate evaluation results of characteristics of a perovskite solar cell using graphene electrodes at different doping concentrations according to an embodiment of the present invention.

16 shows the results of measuring the stability of the current for the perovskite solar cell using a gold chloride-doped graphene electrode according to an embodiment of the present invention.

17 is a flowchart illustrating a method of manufacturing a perovskite solar cell using a graphene electrode according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings and the contents described in the accompanying drawings, but the present invention is not limited or limited to the embodiments.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. In this specification, the singular also includes the plural unless specifically stated otherwise in the phrase. As used herein, “comprises” and / or “comprising” refers to the presence of one or more other components, steps, operations and / or elements. Or does not exclude additions.

As used herein, “an embodiment”, “an example”, “side”, “an example”, etc., should be construed that any aspect or design described is better or advantageous than other aspects or designs. It is not.

In addition, the term 'or' means inclusive or 'inclusive or' rather than 'exclusive or'. In other words, unless stated otherwise or unclear from the context, the expression 'x uses a or b' means any one of natural inclusive permutations.

Also, the singular forms “a” or “an”, as used in this specification and in the claims, generally refer to “one or more” unless the context clearly dictates otherwise or in reference to a singular form. Should be interpreted as

In addition, terms such as first and second used in the present specification and claims 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.

Unless otherwise defined, all terms (including technical and scientific terms) used in the present specification may be used in a sense that can be commonly understood by those skilled in the art. In addition, the terms defined in the commonly used dictionaries are not ideally or excessively interpreted unless they are specifically defined clearly.

On the other hand, in describing the present invention, when it is determined that the detailed description of the related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted. Terminology used herein is a term used to properly express an embodiment of the present invention, which may vary according to a user, an operator's intention, or a custom in the field to which the present invention belongs. Therefore, the definitions of the terms should be made based on the contents throughout the specification.

1 illustrates a structure example of a perovskite solar cell using a graphene electrode according to an embodiment of the present invention.

The perovskite solar cell 100 using the graphene electrode according to the embodiment of the present invention is formed including a graphene transparent electrode whose characteristics are controlled by doping.

To this end, the perovskite solar cell 100 using a graphene electrode according to an embodiment of the present invention is a graphene electrode 110, a hole transport layer 120, a blocking layer 130, an electron transport layer 140 ), And an upper electrode 150.

The graphene electrode 110 is formed by applying an impurity solution to the graphene surface transferred on the substrate.

The substrate may be at least one of a glass substrate, a plastic substrate, and a flexible substrate, and the flexible substrate may be polyethylene glycol (polyethylenterephthalate, PET), polyethylene naphtalate (PEN), and polydimethylsiloxane (PDMS). It may be at least one of).

The graphene electrode 110 is formed by spin coating a p-type impurity solution on the graphene to dope the graphene transferred on the substrate, and the electrode characteristics may be improved in proportion to the doping concentration of the p-type impurity solution. .

In addition, the graphene electrode 110 is formed by a p-type impurity solution of gold chloride (Gold chloride, AuCl ₃ ), the doping concentration may be controlled by the amount of powder of gold chloride.

The p-type impurity solution may be formed of at least one of nitric acid (HNO ₃ ), rhodium chloride (RhCl ₃ ), and trifluoromethanesulfonic acid (TFSA) in addition to gold chloride.

The graphene is manufactured by chemical vapor deposition (CVD), transferred onto the substrate, and then formed by removing poly (methyl methacrylate) (PMMA).

According to an embodiment, the graphene electrode 110 may be formed by growing graphene directly on the substrate or transferring the grown graphene onto the substrate. At this time, the method for growing graphene is not particularly limited.

According to an embodiment, the graphene electrode 110 formed by the chemical vapor deposition (CVD) method may have a hydrophobic surface.

The hole transport layer 120 is deposited on the doped graphene electrode.

The hole transport layer 120 may be formed by spin-coating methanol and a PEDOT: PSS solution on the doped graphene electrode 110 and then evaporating methanol.

For example, the hole transport layer 120 may be formed to have a uniform thickness and composition through a solution process by applying a template material on the graphene electrode 110 surface.

According to an embodiment, the hole transport layer 120 may be a hole transport layer, and may include an inorganic oxide thin film. The inorganic oxide thin film is a p-type inorganic oxide such as tungsten oxide (WO ₃ ), molybdenum trioxide (MoO ₃ ), vanadium oxide (Vanadium (V) oxide, V ₂ O ₅ ), nickel oxide (Nio), or the like. It may be formed.

Thereafter, the hole transport layer 120 may include a PEDOT: PSS thin film formed on the inorganic oxide thin film, and the inorganic oxide thin film and the PEDOT: PSS thin film may function together as a hole transport layer.

The blocking layer 130 is formed of a thin metal oxide having a predetermined thickness by applying a perovskite structure material on the hole transport layer.

The blocking layer 130 may be formed by spin-coating a perovskite structure material and a dimethylformamide (N, N, dimethylformamide) solution on the hole transport layer 120.

For example, the blocking layer 130 is a metal oxide, in addition to titanium dioxide (TiO ₂ ), zirconium, titanium, tin, zinc, zinc oxide, zirconium dioxide (ZrO ₂ ), tantalum oxide (Ta ₂ O ₃ ) It may be formed of a metal oxide in the form of a thin film, such as magnesium oxide (Magnesium oxide, MgO), hafnium (IV) oxide, HfO ₂ .

The electron transport layer 140 is formed on the blocking layer 130.

The electron transport layer 140 may be formed by spin coating a PCBM (Phenyl-C61-butyric acid methyl ester) and toluene solution on the blocking layer 130.

According to an embodiment, the electron transport layer 140 may be an electron transport layer, and may include an inorganic oxide thin film. The inorganic oxide thin film may be formed of an n-type inorganic oxide such as titanium dioxide (TiO ₂ ), zinc oxide (ZnO), or the like.

For example, when the inorganic oxide thin film is an electron transporting layer made of titanium dioxide, the inorganic oxide precursor may be titanium bisammonium lactatodihydroxide (TiBALDH, [CH ₃ CH (O) CO ₂ NH ₄ ] ₂ Ti (OH). ₂ ) and the like can be used.

The upper electrode 150 is formed on the electron transport layer 140.

The upper electrode 150 may be formed of silver (Ag), gold (Au), copper (Cu), aluminum (Al), platinum (Pt), and the like by using a thermal evaporator on the electron transport layer 140. It may be formed of at least one material of the alloy.

For example, the method of forming the upper electrode 150 is not particularly limited.

According to the exemplary embodiment, when the graphene electrode 110 is an anode, the upper electrode 150 may function as a cathode, and in this case, the upper electrode 150 may be a metal having a low work function. It may be formed of aluminum (Al).

According to another embodiment, when the graphene electrode 110 is a cathode, the upper electrode 150 may function as an anode, in which case the upper electrode 150 is a metal having a high work function. Phosphorus silver (Ag) may be formed.

Specific examples of manufacturing a perovskite solar cell using a graphene electrode according to an embodiment of the present invention are as follows.

<Production process of perovskite solar cell using graphene electrode>

Basically, graphene electrode doped with gold chloride (AuCl ₃ ) has a large work function, so the perovskite structure is manufactured based on the pin structure.

1) PEDOT: PSS was deposited to fabricate a hole transport layer on undoped or doped graphene electrodes.

PEDOT: PSS solution was prepared in a methanol: PEDOT: PSS = 2: 1 volume ratio, the prepared solution was spin-coated at 2000rpm for about 1 minute after drop on the graphene electrode.

For example, a spin coating method, which is a coating method in which the prepared solution is dropped on the graphene electrode and rotated at high speed to spread thinly, was used.

Thereafter, the solvent (methanol) was evaporated and heat-treated at 150 ° C. for 20 minutes to form a good film (hole transport layer).

2) Drop 40 wt% MAPbI ₃ / DMF (N, N, dimethyl formamide) solution onto the hole transport layer (PEDOT: PSS / Graphene / Glass) formed on the graphene electrode and spin for 200 seconds at 3000 rpm After coating, the mixture was heat treated at 100 ° C. for 2 minutes to form a barrier layer.

3) Subsequently, a Phenyl-C61-butyric acid methyl ester (PCBM) solution was made of PCBM / toluene (20 mg / 1 mL), and then a blocking layer (MAPbI ₃ (perovskite structural material) / PEDOT: PSS / Graphene / Glass) was spin-coated at 2000 rpm for 60 seconds, and then naturally dried to form an electron transport layer.

4) Finally, an aluminum (Al) electrode was formed on an electron transport layer (PCBM / MAPbI ₃ / PEDOT: PSS / Graphene / Glass) using a thermal evaporator to form an upper electrode.

2 illustrates an example of transferring graphene onto a substrate according to an embodiment of the present invention.

Referring to FIG. 2, a sheet of graphene is transferred onto a glass. The substrate may be a glass substrate, but may be any one of a flexible substrate and a plastic substrate.

For example, graphene is manufactured by chemical vapor deposition (CVD), and a sheet of graphene is supported by poly (methyl methacrylate) (PMMA), floated in deionized water, and then transferred onto a substrate. .

According to an embodiment, the transferred graphene may be dried in air, and then formed on a hot plate and further dried at about 180 ° C. for 2 hours. Thereafter, after removing PMMA using acetone, it may be naturally dried.

3A and 3B illustrate an example of manufacturing doped graphene according to an embodiment of the present invention.

More specifically, Figure 3a shows an example of the doping concentration according to the mixing of nitromethane (Nitro methane) and gold chloride (Gold chloride, AuCl ₃ ), Figure 3b to form a graphene electrode on the graphene / substrate An example is shown.

The graphene electrode of the perovskite solar cell using the graphene electrode according to the embodiment of the present invention is formed by a doping solution doped on the graphene surface transferred on the substrate.

According to the embodiment, the doping solution may be used gold chloride for the production of p-type graphene.

Referring to FIG. 3A, the doping solution according to the mixing of nitromethane and gold chloride may exhibit different doping concentrations depending on the amount of powder of gold chloride.

According to the embodiment, the doping concentration of the doping solution was adjusted to 1mM to 10mM by the amount of gold chloride powder, and after doping to uniformly coat the gold chloride, heat treatment was performed at 100 ° C. for 10 minutes using rapid heat treatment.

Referring to FIG. 3B, according to an exemplary embodiment of the present invention, a doping solution 310 which is a p-type impurity solution is coated on a graphene / substrate, and spin-coated to form a doped graphene electrode. Robesky solar cells can be fabricated.

The doping solution 310 may be any one of solutions showing different doping concentrations according to the amount of gold chloride powder prepared in FIG. 3A.

According to an embodiment, the doping solution 310 is applied onto the graphene / substrate, followed by spin coating for 1 minute at about 2500 rpm. Thereafter, annealing of the p-type impurity solution / graphene / substrate 330 to which the P-type impurity solution is applied is performed to form a graphene electrode 350 using the doped graphene as an electrode. Can be.

Figure 4 shows the experimental results for the doping degree of gold chloride according to an embodiment of the present invention.

More specifically, FIG. 4 shows a graph of experimental results obtained by applying X-ray photoelectron spectroscopy to a gold chloride-doped graphene electrode.

Referring to FIG. 4, XPS intensity (XPS Intensity) according to binding energy (eV) in gold chloride-doped graphene electrode (AuCl ₃ doped graphene) and undoped graphene electrode (Pristine graphene) You can check.

4, the gold (Au) and chlorine (Cl) elements are observed only on the graphene electrode doped with gold chloride. Through this, the p-type impurity solution of gold chloride (AuCl ₃ ) is graphene. It can be seen that it is well doped on the electrode.

5a to 5g show the results of experiments on the surface roughness and the formation of nanoparticles at different doping concentrations according to an embodiment of the present invention.

More specifically, FIGS. 5A to 5F show graphs of experimental results of atomic force microscope (AFM) images and nanoparticle height profiles according to the doping concentration of gold chloride (AuCl ₃ ), and FIG. 5g shows an experimental result graph of surface roughness values according to the doping concentration of gold chloride (AuCl ₃ ).

FIG. 5A shows experimental results of AFM images and nanoparticle height for graphene / substrate including undoped graphene electrodes (Pristine graphene).

Looking at the AFM image in FIG. 5A, it can be seen that the p-type impurity is not doped on the graphene / substrate, and the results of experiments on the nanoparticle height profile show that no height profile is formed. .

FIG. 5B shows experimental results of AFM images and nanoparticle height for graphene / substrate comprising 1 mM gold chloride doped graphene electrode, and FIG. 5C includes graphene electrode doped with 2.5 mM gold chloride. The experimental results of the AFM image and nanoparticle height for the graphene / substrate.

FIG. 5D shows experimental results of AFM images and nanoparticle height for graphene / substrate comprising 5 mM gold chloride doped graphene electrode, and FIG. 5E includes 7.5 mM gold chloride doped graphene electrode. AFM images of the graphene / substrate and the experimental results of the nanoparticle height is shown, Figure 5f is an experiment of the AFM image and nanoparticle height for the graphene / substrate containing a graphene electrode doped with 10 mM gold chloride The results are shown.

5A to 5F, it can be seen that impurities are formed on the graphene / substrate surface in proportion to the increase in the amount of powder of gold chloride (AuCl ₃ ), and the height profile is also increased accordingly.

From these experimental results, it can be seen that gold (Au) nanoparticles are formed by doping with gold chloride. This may be understood that the reduction potential of graphene (0.22eV) is higher than that of gold chloride ions (1.0eV).

Referring to FIG. 5G, surface roughness values (Rq) in graphene / substrate according to undoped graphene electrodes (Pristine) and graphene electrodes doped with gold chloride of 1 mM, 2.5 mM, 5 mM, 7.5 mM and 10 mM, respectively. )can confirm.

As shown in FIG. 5g, it can be seen that the roughness value Rq of the graphene / substrate surface increases as the doping concentration n _D of the doping solution increases depending on the amount of powder of gold chloride.

Figure 6 shows the experimental results for the graphene sheet resistance at different doping concentrations according to an embodiment of the present invention.

More specifically, FIG. 6 shows graphene on a graphene / substrate according to undoped graphene electrodes (Pristine) and graphene electrodes doped with gold chloride doped with 1 mM, 2.5 mM, 5 mM, 7.5 mM and 10 mM, respectively. A graph of the sheet resistance measurement results is shown.

Referring to FIG. 6, it can be seen that the sheet resistance of the graphene electrode gradually decreases as the doping concentration n _D of the doping solution increases depending on the amount of powder of gold chloride.

As shown in FIG. 6, the sheet resistance of the single layer graphene transferred onto the substrate was observed to be about 890 ohm / sq on average, and as the doping concentration of gold chloride (AuCl ₃ ) increased from 1 mM to 10 mM, the sheet resistance of the graphene electrode. It can be seen that gradually decreases from ~ 890ohm / sq to ~ 70ohm / sq. This means that as the doping concentration increases, the characteristics of the graphene electrode are improved.

Figure 7 shows the experimental results for the permeability of graphene at different doping concentrations according to an embodiment of the present invention.

More specifically, FIG. 7 shows the transmission spectrum of graphene according to the undoped graphene electrode (0 mM) and the graphene electrode doped with gold chloride of 1 mM, 2.5 mM, 5 mM, 7.5 mM and 10 mM, respectively. .

Referring to FIG. 7, as the doping concentration of the doping solution according to the powder amount of gold chloride (AuCl ₃ ) increases from 0 to 10 mM, the transmittance at 550 nm is reduced from about 9% to 89.2% by about 8%. You can see that it is very insignificant.

8 shows experimental results of the characteristics of the DC conductivity and the optical conductivity at different doping concentrations according to the embodiment of the present invention.

In more detail, FIG. 8 shows DC conductivity and optical conductivity characteristics through the following [Formula 1] to confirm whether the transparent conductive electrode including the graphene electrode doped with gold chloride (AuCl ₃ ) can be used industrially. The graph of the experimental result confirmed is shown.

 [Equation 1]

Here, T means transmittance, Rs means sheet resistance, and Z0 means free space impedance. Also,

Means optical conductivity,

Means DC conductivity.

Referring to FIG. 8, it can be seen that as the doping concentration n _D of the doping solution increases depending on the amount of powder of gold chloride, the value of DC conductivity / optical conductivity also increases.

In order to use the transparent electrode industrially, the value of DC conductivity / optical conductivity must be at least 35 (the straight line in FIG. 8 graph means minimum value).

As shown in FIG. 8, except for the undoped graphene electrode (Pristine), all doping concentrations of gold chloride of 1mM, 2.5mM, 5mM, 7.5mM and 10mM appear to be larger than the minimum values used in industry. And, when the doping concentration is 7.5mM, DC conductivity / optical conductivity can be seen that the highest value of 38.7. This value is close to the value of indium tin oxide (ITO) (above 45).

Figure 9 shows the experimental results for the work function at different doping concentrations according to an embodiment of the present invention.

More specifically, FIG. 9 illustrates a work function measured by applying a Kelvin probe to each of the undoped graphene electrodes (Pristine) and graphene electrodes doped with gold chloride of 1 mM, 2.5 mM, 5 mM, 7.5 mM, and 10 mM, respectively. The graph shows the measurement result of (Work function).

Referring to FIG. 9, it can be seen that as the doping concentration (n _D ) of the doping solution according to the amount of powder of gold chloride increases, the work function also increases by 0.34 eV from 4.52 eV to 4.86 eV.

These results show that the graphene is p-type by gold chloride (AuCl ₃ ) doping, it can be seen that the work function increases with increasing doping concentration.

10A and 10B illustrate experimental results of graphene field effect transistors at different doping concentrations according to an exemplary embodiment of the present invention.

More specifically, FIG. 10A shows the current-voltage of a graphene field effect transistor according to an undoped graphene electrode (0 mM) and graphene electrodes doped with gold chloride of 1 mM, 2.5 mM, 5 mM, 7.5 mM and 10 mM, respectively. The resultant graphs of the curves and diplock points and mobility are shown, and FIG. 10B shows the resultant graphs of the mobility of electrons and holes of the graphene electrodes calculated from the I _SD -V _G curves.

The drain-source current (I _SD ) and gate voltage (A _BG ) curves of all samples show the conduction characteristics of electrons and holes around the dilock point as is generally observed.

Referring to FIG. 10A, it can be seen that the I _SD −V _G curve is symmetrical in the field effect transistor (FET) of the initial state graphene (0mM). However, it can be seen that the asymmetry changes as the doping concentration (n _D ) gradually increases.

These results generally correspond to the results of asymmetric I _SD -V _G curves due to impurity doping in the graphene FET, and according to the doping concentration of p-type graphene prepared by doping with gold chloride (AuCl ₃ ). Due to changes in structural, optical and electrical properties.

In addition, as the doping concentration increases, the drain current toward the negative gate voltage increases, which is interpreted to be due to the fact that graphene gradually approaches metal properties.

In addition, referring to FIG. 10A, it can be seen that the dirac point moves as the doping concentration n _D of the doping solution increases depending on the amount of powder of gold chloride. In addition, it can be seen that, depending on the chemical doping of graphene due to the exposure of gold chloride, the position of the diplock point shifts toward the positive gate voltage in the I _SD -V _G curve.

This phenomenon is interpreted as a charge transfer according to the gold (Au) adsorbed on the graphene, it can be seen that the di-lock viscosity of the undoped pure graphene (0mM) shifted toward the positive voltage, which means p-type As interpreted due to absorption of atmospheric molecules.

As shown in FIG. 10A, the dilock point may be found to be about 60V when the doping concentration is at most 10 mM.

FIG. 10B illustrates a graph of mobility of electrons and holes of graphene calculated by Equation 2 below from the I _SD -V _G curve of FIG. 10A.

[Formula 2]

Referring to the calculated mobility of the graphene electrode in Figure 10b, the electron mobility is reduced from approximately 3,000 to 550 cm ² / Vs as the doping concentration (n _D ) of the doping solution increases depending on the amount of powder of gold chloride You can see that. On the other hand, the hole mobility (Hole) can be seen that the decrease is small from 2200 to 1600cm ² / Vs as the doping concentration increases.

These results indicate that the graphene electrode doped with p-type impurities due to gold chloride is preferably used as an electrode of the hole transport layer.

FIG. 11 illustrates a scanning electron microscope image of a perovskite solar cell using a graphene electrode according to an embodiment of the present invention.

More specifically, FIG. 11 is a graphene electrode (Graphene) is formed on the substrate (Glass), a hole transport layer (PEDOT: PSS) is formed on the graphene electrode (Graphene), the blocking on the hole transport layer According to an embodiment of the present invention, a layer (MAPbI ₃ , a perovskite structure material) is formed, an electron transport layer (PCBM) is formed on the blocking layer, and an upper electrode (Al electrode) is formed on the electron transport layer. It shows a perovskite solar cell using a graphene electrode.

Referring to FIG. 11, through a scanning microscope image, a ~ 60-nm upper electrode (Al electrode), a ~ 50-nm electron transport layer (PCBM), a ~ 380nm blocking layer (MAPbI ₃ ), and a ~ 40nm hole transport layer (PEDOT): It can be seen that the graphene electrode doped with PSS) and 7.5 mM gold chloride (AuCl ₃ ) is excellently formed on the glass.

12A and 12B illustrate evaluation results of characteristics of a perovskite solar cell using a graphene electrode according to an exemplary embodiment of the present invention.

 More specifically, FIG. 12A illustrates a graph of evaluation of characteristics of a perovskite solar cell using an undoped graphene electrode (Pristine), and FIG. 12B illustrates a perovskite using a graphene electrode doped with 7.5 mM gold chloride. It shows the characteristic evaluation graph of the sky solar cell.

12A and 12B, it can be seen that the graphene electrode doped with 7.5 mM gold chloride is higher in efficiency than the undoped graphene electrode (Pristine).

The reason for this is, firstly, the result of the conductivity improvement of the graphene electrode, and secondly, the work function increases as the doping concentration of the doping solution increases depending on the amount of gold chloride powder.

As the work function increases with increasing doping concentration, the Fermi level of graphene can be placed further down the diplock point, and thus the holes can be moved more easily in the hole transport layer PEDOT: PSS. It can be seen that.

However, although the conductivity is further improved at a higher doping concentration (about 0.9mM), it can be confirmed through Table 1 below that the efficiency is reduced due to the decrease in the transmittance. Therefore, it can be seen that the graphene electrode having the doping concentration of 7.5mM has the best efficiency.

TABLE 1

Figure 13 shows the experimental results for the external quantum efficiency of the perovskite solar cell using a graphene electrode according to an embodiment of the present invention.

More specifically, FIG. 13 shows measurement results of external quantum efficiency (EQE) according to undoped graphene electrodes (Pristine) and graphene electrodes doped with gold chloride of 1 mM, 2.5 mM, 5 mM, 7.5 mM and 10 mM, respectively. The graph is shown.

Referring to FIG. 13, external quantum efficiency is increased in a perovskite solar cell using a graphene electrode doped with 1 mM gold chloride (AuCl ₃ ), compared to a perovskite solar cell using an undoped graphene electrode (0 mM). You can see that it shows a higher value. However, the external quantum efficiency decreases as the doping concentration (n _D ) of the doping solution increases depending on the amount of powder of gold chloride.

This result is interpreted to be related to the decrease in graphene transmittance with increasing doping concentration. In addition, it is already known that the value integrating the external quantum efficiency is theoretically proportional to the short-circuit current density (J _SC ). Referring to the above [Table 1], the value integrating the external quantum efficiency is the short-circuit current density. It can be seen that it shows a dependency tendency of the doping concentration as the value.

14A and 14B illustrate graphs of measurement results of diffusion coefficients and carrier decay times at different doping concentrations and calculation examples of diffusion distances according to embodiments of the present invention.

More specifically, FIG. 14A shows a graph of measurement results of diffusion coefficients between undoped graphene electrodes (0 mM) and graphene electrodes doped with gold chloride of 1 mM, 2.5 mM, 5 mM, 7.5 mM and 10 mM, respectively. FIG. 14B shows a graph of measurement results of carrier decay time according to undoped graphene electrodes (0 mM) and graphene electrodes doped with gold chloride of 1 mM, 2.5 mM, 5 mM, 7.5 mM and 10 mM, respectively.

14A and 14B, the diffusion coefficient Dn and the carrier decay time at the current density at the doping concentration n _D of the doping solution according to the powder amount of gold chloride (

), You can check the graph of the measurement result.

Measured diffusion coefficient (Dn) and carrier decay time (

The diffusion distance can be calculated from the following [Equation 3] from the two results.

 [Equation 3]

Referring to the above [Table 1], it can be seen that the diffusion distance is best at 370nm when the doping concentration is 7.5mM.

15A to 15F illustrate evaluation results of characteristics of a perovskite solar cell using graphene electrodes at different doping concentrations according to an embodiment of the present invention.

More specifically, FIGS. 15A to 15F illustrate graphene electrodes according to doping concentrations of undoped graphene electrodes (Pristine, 0 mM) and doping concentrations of 1 mM, 2.5 mM, 5 mM, 7.5 mM and 10 mM gold chloride (AuCl3). The graph shows the results of measuring 24 perovskite solar cells, respectively.

Referring to FIG. 15A, the measurement result of 24 perovskite solar cells according to the undoped graphene electrode (0 mM) shows 10.24 ± 1.29%.

In addition, referring to Figure 15b, the results of measuring 24 perovskite solar cells using a graphene electrode according to the doping concentration of gold chloride of 1mM shows 13.8 ± 1.32%, referring to Figure 15c, 2.5mM Twenty-four perovskite solar cells were measured using graphene electrodes according to the doping concentration of gold chloride, showing 14.58 ± 1.28%.

In addition, referring to Figure 15d, the results of measuring 24 perovskite solar cells using a graphene electrode according to the doping concentration of 5mM gold chloride shows 15.89 ± 1.17%, referring to Figure 15e, 7.5mM 24 perovskite solar cells were measured using graphene electrodes according to the doping concentration of gold chloride of 15.94 ± 1.26%.

Referring to FIG. 15F, the measurement results of 24 perovskite solar cells using graphene electrodes according to the doping concentration of 10 mM gold chloride showed 14.88 ± 1.39%.

Referring to Figure 15a to 15f, it can be seen that the average doping concentration in the average of 15.94% at 7.5mM.

16 shows the results of measuring the stability of the current for the perovskite solar cell using a gold chloride-doped graphene electrode according to an embodiment of the present invention.

In more detail, FIG. 16 illustrates a graph showing the results of measuring the stability of the current for a perovskite solar cell using a graphene electrode doped with 7.5 mM gold chloride (AuCl ₃ ).

For example, FIG. 16 is a graph of a measurement result of a perovskite solar cell using a graphene electrode doped with 7.5 mM gold chloride while the encapsulation environment is maintained at 50% humidity without applying encapsulation technology. It is shown.

Referring to Figure 16, the perovskite solar cell using a graphene electrode doped with 7.5mM gold chloride can be seen that the current density hardly changes even after 100 hours of light irradiation.

Accordingly, it can be seen that the perovskite solar cell using the graphene electrode according to the embodiment of the present invention exhibits excellent stability characteristics, and the graphene electrode can be applied to the flexible device based on these results. It can be applied to various optoelectronic devices.

17 is a flowchart illustrating a method of manufacturing a perovskite solar cell using a graphene electrode according to an embodiment of the present invention.

Referring to FIG. 17, in operation 1710, graphene is transferred onto a substrate.

Thereafter, an impurity solution is applied to the graphene surface transferred in step 1720 to form a graphene electrode.

In operation 1720, a graphene electrode is formed by spin coating a p-type impurity solution on the graphene to dope the transferred graphene on the substrate, and the electrode characteristics of the graphene electrode are proportional to the doping concentration of the p-type impurity solution. It may be a step of improving.

The graphene electrode is formed by a p-type impurity solution of gold chloride (AuCl ₃ ), and the doping concentration may be controlled by the amount of powder of gold chloride.

In step 1730, a hole transport layer is deposited on the doped graphene electrode.

Step 1730 may be a step of spin-coating methanol and a PEDOT: PSS solution on the doped graphene electrode, and then evaporating methanol to deposit a hole transport layer.

In operation 1740, a perovskite structure material is coated on the hole transport layer to form a barrier layer of a thin metal oxide layer.

Step 1740 may be a step of forming the blocking layer of the perovskite structure material by spin coating a perovskite structure material and dimethylformamide (N, N, dimethylformamide) solution on the hole transport layer.

In operation 1750, an electron transport layer is formed on the blocking layer.

Step 1750 may be a step of forming a electron transfer layer, which is an electron transfer layer, by spin-coating a phenyl-C61-butyric acid methyl ester (PCBM) and toluene solution on a single layer.

In operation 1760, an upper electrode is formed on the electron transport layer.

Step 1760 is performed on at least one of silver (Ag), gold (Au), copper (Cu), aluminum (Al), platinum (Pt) and alloys thereof using a thermal evaporator on the electron transport layer. It may be a step of forming an upper electrode from a material.

Although the embodiments have been described by the limited embodiments and the drawings as described above, various modifications and variations are possible to those skilled in the art from the above description. For example, the described techniques may be performed in a different order than the described method, and / or components of the described systems, structures, devices, circuits, etc. may be combined or combined in a different form than the described method, or other components. Or even if replaced or substituted by equivalents, an appropriate result can be achieved.

Therefore, other implementations, other embodiments, and equivalents to the claims are within the scope of the claims that follow.

Claims (16)

1. A graphene electrode formed by applying an impurity solution to a graphene surface transferred on a substrate;

   A hole transport layer deposited on the doped graphene electrode;

   A barrier layer formed of a metal oxide of a thin film having a predetermined thickness by applying a material having a perovskite structure on the hole transport layer;

   An electron transport layer formed on the blocking layer; And

   An upper electrode formed on the electron transport layer

   Perovskite solar cell using a graphene electrode comprising a.
2. The method of claim 1,

   The graphene electrode is

   In order to dope the graphene transferred on the substrate is formed by spin coating a p-type impurity solution on the graphene, the graphene characterized in that the electrode characteristics are improved in proportion to the doping concentration of the p-type impurity solution Perovskite solar cell using an electrode.
3. The method of claim 2,

   The graphene electrode is

   The perovskite solar cell using a graphene electrode is formed by the p-type impurity solution (Gold chloride, AuCl ₃ ), the doping concentration is controlled by the amount of powder of the gold chloride.
4. The method of claim 3,

   The p-type impurity solution

   In addition to the gold chloride, perovskite solar cell using a graphene electrode formed of at least one of nitric acid (HNO ₃ ), rhodium chloride (RhCl ₃ ) and trifluoromethanesulfonic acid (TFSA).
5. The method of claim 2,

   The graphene is

   A perovskite solar cell using a graphene electrode which is manufactured by chemical vapor deposition (CVD) and transferred onto the substrate, and then formed by removing poly (methyl methacrylate) (PMMA).
6. The method of claim 1,

   The hole transport layer is

   A perovskite solar cell using a graphene electrode formed by evaporating the methanol after spin coating a methanol (methanol) and a PEDOT: PSS solution on the doped graphene electrode.
7. The method of claim 1,

   The blocking layer

   A perovskite solar cell using a graphene electrode formed by spin coating the perovskite structure material and dimethylformamide (N, N, dimethylformamide) solution on the hole transport layer.
8. The method of claim 1,

   The electron transport layer

   A perovskite solar cell using a graphene electrode formed by spin coating a PCBM (Phenyl-C61-butyric acid methyl ester) and a toluene solution on the blocking layer.
9. The method of claim 1,

   The upper electrode is

   Using a thermal evaporator on the electron transport layer to at least one material of silver (Ag), gold (Au), copper (Cu), aluminum (Al), platinum (Pt) and alloys thereof Perovskite solar cell using a graphene electrode formed.
10. Transferring graphene onto the substrate;

    Forming a graphene electrode by applying an impurity solution to the transferred graphene surface;

    Depositing a hole transport layer on the doped graphene electrode;

    Applying a material having a perovskite structure on the hole transport layer to form a barrier layer of a metal oxide having a predetermined thickness;

    Forming an electron transport layer on the blocking layer; And

    Forming an upper electrode on the electron transport layer

    Method for producing a perovskite solar cell using a graphene electrode comprising a.
11. The method of claim 10,

    Forming the graphene electrode

    In order to dope the graphene transferred on the substrate to form a graphene electrode by spin coating a p-type impurity solution on the graphene, the electrode of the graphene electrode in proportion to the doping concentration of the p-type impurity solution Method for producing a perovskite solar cell using a graphene electrode, characterized in that to improve the characteristics.
12. The method of claim 11,

    The graphene electrode is

    Formed by the p-type impurity solution (Gold chloride, AuCl ₃ ), the doping concentration is a method of manufacturing a perovskite solar cell using a graphene electrode, characterized in that controlled by the amount of powder of the gold chloride. .
13. The method of claim 10,

    Depositing the hole transport layer is

    After the spin coating the methanol (methanol) and PEDOT: PSS solution on the doped graphene electrode, a method of manufacturing a perovskite solar cell using a graphene electrode to evaporate the methanol to deposit the hole transport layer.
14. The method of claim 10,

    Forming the blocking layer

    Peptide using a graphene electrode to form the blocking layer of the perovskite structure material by spin coating the perovskite structure material and dimethylformamide (N, N, dimethylformamide) solution on the hole transport layer Method for manufacturing a robe sky solar cell.
15. The method of claim 10,

    Forming the electron transport layer

    Preparation of a perovskite solar cell using a graphene electrode to form the electron transfer layer as an electron transfer layer by spin coating a PCBM (Phenyl-C61-butyric acid methyl ester) and toluene solution on the blocking layer Way.
16. The method of claim 10,

    Forming the upper electrode

    Using a thermal evaporator on the electron transport layer to at least one material of silver (Ag), gold (Au), copper (Cu), aluminum (Al), platinum (Pt) and alloys thereof Method of manufacturing a perovskite solar cell using a graphene electrode to form the upper electrode.

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