KR101722579B1 - Photoactive layer for and the preparing method thereof - Google Patents

Abstract

The present invention relates to a photoactive layer for a quantum dot photovoltaic cell, a solar cell comprising the same, and more particularly to a photovoltaic layer for a quantum dot solar cell and a method of manufacturing the same. The band gap and the like of the solar cell can be improved to improve the short-circuit current density, the open-circuit voltage, the performance index, and the power conversion efficiency of the solar cell including the same. And a manufacturing method thereof.

Description

TECHNICAL FIELD The present invention relates to a photoactive layer for a quantum dot solar cell, a solar cell including the same, and a method for manufacturing the same.

The present invention relates to a photoactive layer for a quantum dot photovoltaic cell, a solar cell comprising the same, and more particularly to a photovoltaic layer for a quantum dot solar cell and a method of manufacturing the same. The band gap and the like of the solar cell can be improved to improve the short-circuit current density, the open-circuit voltage, the performance index, and the power conversion efficiency of the solar cell including the same. And a manufacturing method thereof.

'Quantum dot' is a nano-sized semiconductor structure particle that emits light when stimulated by energy such as light. It is a material that changes the color of light emitted according to particle size.

The principle is explained in detail as follows. As the size of the material becomes smaller and the dimension of the material becomes lower, the electron state densities and energies are different. Therefore, the properties of the materials are also different depending on the dimensions. For example, in small nanoparticles of several nm in size, A quantum confinement effect appears.

In addition, reducing the dimension means that electrons are confined to a region smaller than the debris wave length in a strict sense. The zero-dimensional quantum dot is not the point that there is no area at all, but actually the dimension is three-dimensionally larger than the debris wave length Small sample refers to. In quantum mechanics, the waves involved in all material particles with momentum, ie debris wave length, depend on the material and are about 10 nm in the case of semiconductors. Semiconductor quantum dots consist of about one million electrons, but in practice, the number of free electrons that are unconstrained is about 1 to 100, because electrons are tightly bound to the material nucleus. Therefore, free electrons in quantum dots can be represented by waves, and energy and state density are quantized.

Therefore, as the size of the semiconductor nanoparticles of 10 nm or less, which is smaller than the debris wave length, decreases, the band gap energy of the semiconductor particles relatively increases. Therefore, even if the same material is used, It is possible to make dozens of colors by adjusting, and the display [Seth Coe-Sullivan, Wing-Keung Woo, Jonathan S. Steckel, Moungi Bawendi, Vladimir Bulovic, "Tuning the performance of hybrid organic / inorganic quantum dot light- Organic Electronics, vol. 4 123-130 (2003)], as well as the development of next-generation electronic products such as recording devices, various sensors and nano computers, as well as biological, pharmaceutical [X. Michalet, FF Pinaud, LA Bentolila, 1 JM Tsay, 1 S. Doose, 1. The application potential is significant, such as JJ Li, 1 G. Sundaresan, AM Wu, SS Gambhir, S. Weiss1, "Quantum Dots for Live Cells, in Vivo Imaging, and Diagnostics" SCIENCE VOL 307, 538-544 Is being evaluated.

It is an object of the present invention to provide a method for controlling a short circuit current density in a solar cell including the spraying pressure, a kind of a ligand, a concentration of a ligand, an immersion time for a ligand exchange, a band gap of a quantum dot, , Open-circuit voltage, performance index, power conversion efficiency and the like can be improved, a solar cell including the same, and a method of manufacturing the same.

The present invention provides a method of manufacturing a PbS quantum dot semiconductor light emitting device, comprising: a first step of spraying a solution containing a PbS quantum dot on an electron transport layer to form a PbS quantum dot semiconductor layer; A second step of immersing the PbS quantum dot semiconductor layer in a ligand solution containing EDT (1,2-Ethanedithiol) solution and TBAI (tetrabutylammonium iodide) solution to bind a ligand on the surface of the PbS quantum dot semiconductor layer; And washing the PbS quantum dot semiconductor layer to which the ligand is bound, in accordance with an embodiment of the present invention.

In one preferred embodiment of the present invention, the electron transport layer may include one selected from the group consisting of ZnO, TiO 2, SnO 2, ITO, and derivatives thereof.

In a preferred embodiment of the present invention, the PbS quantum dot included in the solution containing the PbS quantum dot of the first step may have a band gap of 1.0 to 1.9 eV.

In one preferred embodiment of the present invention, the PbS quantum dots included in the solution containing the PbS quantum dot in the first step may have an average particle diameter of 1 nm to 20 nm.

In one preferred embodiment of the present invention, the PbS quantum dots contained in the solution containing the PbS quantum dots of the first stage are selected from the group consisting of oleic acid, oleyl amine, trioctylphosphine oxide ) And an alkyl-based surfactant, may be used.

In a preferred embodiment of the present invention, spraying in step 1 may be performed at a pressure of 0.1 to 100 psi.

In a preferred embodiment of the present invention, the concentration of EDT in the EDT solution may be 1 mM to 1 M.

In a preferred embodiment of the present invention, the TBAI solution may have a concentration of TBAI of 0.1 mM to 5 M.

In a preferred embodiment of the present invention, the ligand solution may contain EDT solution and TBAI solution in a molar ratio of 1: 0.1-10.

In a preferred embodiment of the present invention, the immersion in the second step may be performed for 1 to 600 seconds.

In a preferred embodiment of the present invention, the washing in step 3 is performed using a solvent such as acrylonitrile (ACN), ethanol (EtOH), methanol (MeOH, methanol), isopropyl alcohol, ), Dimethylformamide (DMF), and dimethyl sulfoxide (DMSO). The solvent may be selected from the group consisting of dimethylformamide (DMF) and dimethyl sulfoxide (DMSO).

Another aspect of the present invention provides a photoactive layer for a quantum dot solar cell manufactured by the above method.

Another aspect of the present invention provides a photoactive layer for a quantum dot solar cell comprising a PbS quantum dot wherein a thioalkyl sulfanyl group and a tetra (alkyl) salt are bound to the surface as a ligand :

In one preferred embodiment of the present invention, the thioalkyl sulfanyl group and the tetra (alkyl) salt may be contained on the surface in a molar ratio of 1: 0.1 to 10.

In a preferred embodiment of the present invention, the PbS quantum dot may have an average particle diameter of 1 nm to 20 nm.

In one preferred embodiment of the present invention, the photoactive layer may have an average thickness of 140 nm to 150 nm.

Still another aspect of the present invention relates to a transparent substrate; An electron transfer layer provided on one surface of the transparent substrate; A photoactive layer for the quantum dot solar cell formed on an upper surface of the electron transport layer; A hole transport layer provided on an upper surface of the photoactive layer; And a counter electrode provided on the hole transport layer.

In a preferred embodiment of the present invention, the quantum dot solar cell may have a Voc of 0.3 to 1.0 V, a Jsc of 5 to 40 mA / cm 2, an FF of 0.3 to 0.8, and a PCE of 2.0 to 9.0%.

According to the present invention, spraying may be performed at room temperature and atmospheric pressure in order to produce a photoactive layer for a quantum dot solar cell through spraying, and spraying pressure, kind of ligand, concentration of ligand, immersion time for ligand exchange, Band gap and the like to an optimal range, the short-circuit current density, the open-circuit voltage, the figure of merit and the power conversion efficiency in the solar cell including the same can be improved.

1 is a schematic view showing a method for manufacturing a photoactive layer for a quantum dot solar cell according to a preferred embodiment of the present invention.
2 is a graph showing the absorbance spectrum according to the bandgap of the PbS quantum dot.
3 is a schematic and SEM image showing a cross section of a solar cell according to a preferred embodiment of the present invention.
4 is an image of a solar cell including a photoactive layer according to a preferred embodiment of the present invention.
5 is a graph showing JV characteristics according to a jetting pressure of a quantum dot solution in a method of manufacturing a solar cell according to a preferred embodiment of the present invention.
6 is a scanning electron microscope (SEM) image of a surface of a quantum dot semiconductor layer according to a jetting pressure of a quantum dot solution in a method of manufacturing a solar cell according to an embodiment of the present invention.
7 is a graph showing JV characteristics according to the kind and concentration of the ligand in a preferred embodiment of the present invention.
FIG. 8 is a graph showing JV characteristics according to time for immersing a photoactive layer in a ligand solution in a method of manufacturing a solar cell according to a preferred embodiment of the present invention.
9 is a view illustrating a method of manufacturing a solar cell according to a preferred embodiment of the present invention.

The present invention provides a method of manufacturing a PbS quantum dot semiconductor light emitting device, comprising: a first step of spraying a solution containing a PbS quantum dot on an electron transport layer to form a PbS quantum dot semiconductor layer; A second step of immersing the PbS quantum dot semiconductor layer in a ligand solution containing EDT (1,2-Ethanedithiol) solution and TBAI (tetrabutylammonium iodide) solution to bind a ligand on the surface of the PbS quantum dot semiconductor layer; And washing the PbS quantum dot semiconductor layer having the ligand bound thereto. The present invention provides a method for manufacturing a photoactive layer for a quantum dot solar cell, which comprises spraying, spraying, spraying, The concentration of the ligand, the immersion time for the ligand exchange, and the band gap of the quantum dot to be used are adjusted to an optimum range, the short circuit current density, open voltage, performance index and power conversion efficiency Etc. can be improved. Hereinafter, the present invention will be described in more detail by step.

In the method of manufacturing a photoactive layer for a quantum dot solar cell according to the present invention, the first step is a step of spray-spraying a solution containing a PbS quantum dot on the electron transport layer to form a PbS quantum dot semiconductor layer, May be applied onto the electron transport layer to form a photoactive layer.

At this time, the PbS quantum dots included in the solution containing the PbS quantum dot in the first step may have a band gap of 1.0 to 1.9 eV, preferably 1.3 to 1.7 eV, and more preferably have a band gap of 1.3 to 1.5 eV. As the bandgap of the PbS quantum dot becomes smaller, the open-circuit voltage Voc and the short-circuit current density Jsc tend to decrease. When the PbS quantum dot is in the above range, it can exhibit excellent power conversion efficiency (PCE).

The PbS quantum dots included in the solution containing the PbS quantum dot in the first step may have an average particle diameter of 1 nm to 20 nm, and preferably 2 nm to 8 nm. When the particle diameter of the PbS quantum dots is less than 1 nm, there is a problem that uniform preparation is difficult, and even when the PbS quantum dots exceed 20 nm, uniform production and dispersion are difficult.

The PbS quantum dot contained in the solution containing the PbS quantum dot in the first step may be capped with an acid and the acid may be capped at the quantum dot to bind the ligand in a subsequent step But are preferably capped with at least one acid selected from the group consisting of oleic acid, oleyl amine, trioctylphosphine oxide and alkyl surfactants, May be used. More preferably, those oleic acid-capped can be used.

In addition, the PbS quantum dot semiconductor layer is formed through spraying, so that the characteristics of the quantum dot can be preserved even after the PbS quantum dot semiconductor layer is formed. At this time, the pressure at the time of spraying can be adjusted by using an unreactive gas, and the distribution of quantum dots in the photoactive layer may be changed according to the pressure at the time of spraying, Can vary. The spraying may be performed at a pressure of 0.1 to 100 psi, preferably at a pressure of 2 to 9 psi, and more preferably at a pressure of 4 to 8 psi. When the spraying is performed at less than 0.1 psi, the formation of the thin film is uneven. When the spraying is performed at more than 100 psi, it is difficult to control the thickness of the thin film.

At this time, the spraying may be performed using a spray gun including three separate injection ports. The injection port may include a nitrogen gas inlet for atomization, a pressure regulating lift inlet, and an inlet for a solution of the material to be deposited.

In addition, the electron transport layer may be an n-type semiconductor layer containing one species selected from the group consisting of ZnO, TiO 2, SnO 2, ITO and its derivatives, preferably ZnO.

In the method for manufacturing a photoactive layer for a quantum dot solar cell according to the present invention, the step 2 is a step of immersing the PbS quantum dot semiconductor layer in a ligand solution containing EDT (1,2-Ethanedithiol) solution and TBAI (tetrabutylammonium iodide) Bonding the ligand to the surface of the quantum dot semiconductor layer, wherein the characteristics of the quantum dot semiconductor layer can be determined by bonding the two ligands to the surface of the PbS quantum dot semiconductor layer. Specifically, since the ligand affects the surface bonding defect position of the quantum dot, the quantum dot, the distance between quantum dots, and the energy level of the quantum dot, the characteristics of the quantum dot semiconductor layer can be determined by combining the two kinds of ligands.

At this time, the concentration of EDT in the EDT solution may be 1 mM to 1 M, more preferably 5 mM to 15 mM. When the concentration of EDT is less than 1 mM, it is difficult to control the concentration accurately. When the concentration exceeds 1 M, it is difficult to remove residual EDT.

In addition, the concentration of TBAI in the TBAI solution may be 0.1 mM to 5 M, and more preferably 10 mM to 50 mM. When the concentration of the TBAI is less than 0.1 mM, it is difficult to control the concentration accurately, and when the concentration exceeds 5 M, it is difficult to remove the residual TBAI.

The concentration of the ligand solution containing EDT (1,2-Ethanedithiol) solution and TBAI (tetrabutylammonium iodide) solution is preferably 1 to 20 mM, more preferably 2 to 8 mM. The characteristics of the quantum dot semiconductor layer can be determined according to the concentration of the ligand solution even when the mixing ratio of the two kinds of solutions is maintained.

At this time, the ligand solution may contain EDT solution and TBAI solution in a molar ratio of 1: 0.1 to 10, more preferably 1: 3.5 to 4. The ligand solution can improve the short circuit current density, the open-circuit voltage, the performance index, and the power conversion efficiency in the solar cell including the EDT solution and the TBAI solution at the above-mentioned molar ratio.

In addition, the immersion in the second step may be performed for 1 to 600 seconds, preferably 10 to 110 seconds, and more preferably 30 to 100 seconds. The characteristics of the quantum dot semiconductor layer can be changed according to the immersion time, and thus the short circuit current density, open voltage, performance index, and power conversion efficiency in the solar cell including the quantum dot semiconductor layer can be improved. If the immersion is performed for less than 10 seconds, uniform treatment is difficult, and if the immersion is performed for more than 110 seconds, the thin film becomes uneven.

In the method of manufacturing a photoactive layer for a quantum dot solar cell according to the present invention, the step 3 is a step of washing and drying the PbS quantum dot semiconductor layer to which the ligand is bonded, wherein the washing removes a ligand not bound to the quantum dot semiconductor layer (ACN), ethanol (EtOH), methanol (MeOH, methanol), isopropyl alcohol, water (H2O), and water The solvent may be at least one solvent selected from the group consisting of dimethylformamide (DMF) and dimethyl sulfoxide (DMSO), and more preferably, acrylonitrile (ACN, acrilonitrile ) Solvent. ≪ / RTI >

The present invention provides a photoactive layer for a quantum dot solar cell manufactured by the above-described method.

The present invention also provides a photoactive layer for a quantum dot solar cell comprising a PbS quantum dot wherein a thioalkylsulfanyl group and a tetra (alkyl) ammonium salt are bound to a surface as a ligand. The alkyl group of thioalkylsulfanyl may be any one of C1 to C5, preferably C1 to C3, and more preferably C2. The alkyl group of the tetraalkylammonium salt may be any one of C1 to C5, preferably C4 to C5, and more preferably C4.

At this time, the photoactive layer for the quantum dot solar cell may include the thioalkyl sulfanyl group and the tetra (alkyl) ammonium salt in a molar ratio of 1: 0.1 to 10 on the surface, Preferably in a molar ratio of 1: 0.2 to 3. The short-circuit current density, the open-circuit voltage, the figure of merit, and the power of the solar cell including the thioalkyl sulfanyl group and the tetra (alkyl) ammonium salt in the above- Conversion efficiency and the like can be improved.

At this time, the PbS quantum dot may have an average particle diameter of 1 nm to 20 nm, preferably 2 nm to 8 nm. When the particle diameter of the PbS quantum dots is less than 1 nm, there is a problem that uniform preparation is difficult, and even when the PbS quantum dots exceed 20 nm, uniform production and dispersion are difficult.

In addition, the photoactive layer may have an average thickness of 20 nm to 10,000 nm, preferably an average thickness of 40 nm to 800 nm, more preferably 140 nm to 150 nm, still more preferably May have an average thickness of 140 nm to 145 nm. When the thickness of the photoactive layer is less than 40 nm, there is a problem that the absorption of light is limited. When the thickness of the photoactive layer is more than 80 nm, the electron transporting property is decreased.

Still another aspect of the present invention relates to a transparent substrate; An electron transfer layer provided on one surface of the transparent substrate; A photoactive layer for the quantum dot solar cell formed on an upper surface of the electron transport layer; A hole transport layer provided on an upper surface of the photoactive layer; And a counter electrode provided on the hole transport layer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In the quantum dot solar cell according to the present invention, the transparent substrate may be formed of indium tin oxide (ITO), fluorine doped tin oxide (FTO), aluminum doped zinc oxide (AZO), indium gallium zinc oxide (IGZO) Polyethylene terephthalate (PEN), polyethylene naphthalate (PEN), and polyimide. Preferably, the substrate may be an ITO substrate.

The electron transport layer may include at least one n-type semiconductor selected from the group consisting of ZnO, TiO2, SnO2, ITO, and derivatives thereof, preferably ZnO.

The quantum dot solar cell according to the present invention is characterized in that the photoactive layer for the quantum dot solar cell formed on the upper surface of the electron transport layer has a spin injection pressure, a kind of ligand, a concentration of the ligand, an immersion time for ligand exchange, Gaps and the like to an optimal range, the short circuit current density, open voltage, figure of merit and power conversion efficiency in the solar cell including the same can be improved. Specifically, the solar cell according to the present invention may have a Voc of 0.4 to 0.6 V, a Jsc of 7 to 15 mA / cm ² , a FF of 0.45 to 0.65, a PCE of 2.0 to 4.0%, and preferably a Voc Of 0.5 to 0.6 V, Jsc of 10 to 15 mA / cm ² , FF of 0.55 to 0.65, and PCE of 3.0 to 4.0%.

The quantum dot solar cell according to the present invention includes a hole transport layer provided on an upper surface of the photoactive layer. The hole transport layer may include at least one p-type semiconductor selected from the group consisting of molybdenum oxide, tungsten oxide, nickel oxide, and PEDOT: PSS, and molybdenum oxide may be preferably used.

Further, the quantum dot solar cell according to the present invention includes a counter electrode provided on one surface of the hole transport layer. Wherein the counter electrode is selected from the group consisting of silver, gold, aluminum, copper, indium tin oxide (ITO), fluorine doped tin oxide (FTO), aluminum doped zinc oxide (AZO), and indium gallium zinc oxide And may be an electrode including at least one kind of silver, preferably a silver electrode.

Hereinafter, the present invention will be described in more detail with reference to the following examples. The following examples are provided to illustrate the present invention, but the scope of the present invention is not limited thereto.

[ Example ]

Example  One. Qdot  Manufacture of solar cells

(1) An n-type ZnO layer was laminated on an ITO / glass substrate by an in-situ sol-gel method to form an electron transport layer on a transparent substrate. At this time, the resistance of the electron transport layer is 20? /? Or less. Specifically, a ZnO precursor solution (a solution of 0.45 M zinc acetate hydrate dissolved in 2-methoxyethanol / ethanolamine) was spin-coated on an ITO / glass substrate at 4000 rpm for 15 seconds, Followed by heat treatment to form an electron transport layer.

A solution of oleic acid capped PbS quantum dots (solvent: ~ 50 ml / mL octane) synthesized by a conventional solution phase-based method was applied to the electron transport layer (ZnO layer) at a pressure of 2.9 to 8.7 psi And injected through a jetting nozzle to form a PbS quantum dot semiconductor layer. At this time, the quantum dot solution was sprayed using a spray gun including three separate injection ports. The injection port includes a nitrogen gas injection nozzle for atomization, a pressure regulating lift nozzle, and an injection nozzle for a solution of the substance to be deposited. At this time, the thickness of the PbS quantum dot semiconductor layer was 140 to 145 nm.

(2) The PbS quantum dot semiconductor layer was immersed in a ligand solution containing 8 mM of 1,2-ethanethiol (EDT) and 30 mM of tetrabutylammonium iodide (TBAI) for 60 seconds Thereby bonding the ligand to the surface of the PbS quantum dot semiconductor layer. At this time, the spraying process and the ligand exchange were carried out at normal temperature and normal pressure.

(3) The PbS quantum dot semiconductor layer was washed with acetonitrile (ACN) solution and dried with nitrogen gas to prepare a photoactive layer for a quantum dot solar cell.

Thereafter, a hole transport layer (MoOx layer having a thickness of ~ 10 nm) and an Ag counter electrode were laminated to complete a solar cell.

Example  2 to 14. Qdot  Manufacture of solar cell 2

A solar cell was fabricated in the same manner as in Example 1, except that Example 1 was performed under the same conditions as in Table 1 below.

PbS quantum dot semiconductor layer fabrication Ligand exchange PbS quantum dot band gap
(eV) PbS quantum dot
Average particle size
(nm) Semiconductor layer thickness
(mm) Spray nozzle pressure
(psi) EDT
(mM) TBAI
(mM) Immersion time
(second) Example 1 1.48 3 60 2.9 8 30 60 Example 2 1.48 3 150 5.8 8 30 60 Example 3 1.48 3 150 8.7 8 30 60 Example 4 1.48 3 250 5.8 4 15 60 Example 5 1.48 3 300 5.8 8 30 60 Example 6 1.48 3 500 5.8 12 40 60 Example 7 1.48 3 300 5.8 8 30 10 Example 8 1.48 3 300 5.8 8 30 30 Example 9 1.48 3 300 5.8 8 30 50 Example 10 1.48 3 300 5.8 8 30 70 Example 11 1.48 3 300 5.8 8 30 90 Example 12 1.61 3 300 5.8 8 30 50 Example 13 1.48 3 300 5.8 8 30 50 Example 14 1.34 3 300 5.8 8 30 50

Comparative Example  1-2. Qdot  Manufacture of solar cells 3

A solar cell was prepared in the same manner as in Example 1 except that Example 1 was conducted under the conditions shown in Table 2 below.

PbS quantum dot semiconductor layer fabrication Ligand exchange PbS quantum dot band gap
(eV) PbS quantum dot
Average particle size
(nm) thickness
(mm) Spray nozzle pressure
(psi) EDT
(mM) TBAI
(mM) Immersion time
(second) Comparative Example 1 1.48 3 300 5.8 8 0 50 Comparative Example 2 1.48 3 300 5.8 0 30 50 Comparative Example 3 1.48 3 300 5.8 0 0 0

[ Experimental Example ]

Experimental Example  1. Cross-section analysis of solar cell elements

A cross section of the solar cell element of Example 2 was observed using a cross-section field emission scanning electron microscope (SEM). The results are shown in Fig.

4, it was confirmed that ZnO was formed on the ITO transparent substrate, a PbS quantum dot semiconductor layer was stacked thereon, and molybdenum oxide and silver were sequentially stacked on the semiconductor layer.

Experimental Example  2. Qdot  Depending on the spray pressure range of the solution Qdot  Performance analysis of solar cell

In order to confirm the performance of the quantum dot solar cell according to the injection pressure range of the quantum dot solution sprayed from the spray nozzle, the characteristics of the solar cell prepared in Examples 1 to 3 were measured using a solar simulator of 1.5 AM 100 mW / , Oriel], AM1.5 filter and Keithley SMU2400), and the results are shown in Table 3 and FIG.

More specifically, the open circuit voltage (Voc: V) and the photocurrent density (Jsc: mA / cm2) were analyzed using the JV curve of FIG. Is calculated using the following equations (1) and (2), and is shown in Table 1.

[Equation 1]

Filling factor (%) = ((J x V) max / Jsc x Voc) x 100

Where J is the Y-axis value of the conversion efficiency curve, V is the X-axis value of the conversion efficiency curve, and the photocurrent density (Jsc, mA / cm2) and Voc are the intercept values of the respective axes.

&Quot; (2) "

? (%) = [(Voc x Jsc x FF) / (Pin x S)] x 100

(Open-circuit voltage, V), Jsc is a current (a short-circuit current, mA) when the voltage is zero, FF is a theoretical maximum voltage and a maximum current, Pin is the intensity of the irradiated light (100 mW / cm ² ), and S is the area of the electrode (0.9 cm ² ).

In addition, the surface of the photoactive layer of each of Examples 1 to 3 was observed using a scanning electron microscope (FE-SEM), and the results are shown in FIG.

spray
Pressure (psi) Voc
(V) Jsc
(mAcm ^-2 ) FF PCE (%) Example 1 2.9 0.58 7.04 0.49 2.02 Example 2 5.8 0.56 11.71 0.51 3.38 Example 3 8.7 0.56 10.85 0.51 3.08

According to Table 3 and FIG. 5, it can be seen that increasing the spray pressure from 2.9 psi to 5.8 psi increases the PCE value from 2.02% to 3.38%. However, it can be seen that increasing the spray value to 8.7 psi slightly reduces the PCE value to 3.08%.

Also, the Voc and FF values are similar in all devices, but the Jc value is different. The difference in Jsc values is not due to the exciton generation rate, but is due to charge extraction in the quantum dot layer. However, no significant difference can be found for the continuity of the quantum dot layer produced within a certain pressure range. The spray pressure is optimized at 5.8 psi.

Experimental Example  3. Ligand  Depending on the type Qdot  Performance analysis of solar cell

In order to confirm the performance of the quantum dot solar cell according to the kind of the ligand, Voc, Jsc and FF of the quantum dot solar cells of Examples 4 to 6 were measured in the same manner as Experimental Example 2, 7.

Ligand Voc (V) Jsc (mAcm ^-2 ) FF PCE (%) Comparative Example 1 EDT 8 mM 0.55 7.14 0.55 2.17 Comparative Example 2 TBAI 30 mM 0.45 12.23 0.47 2.53 Example 4 TBAI 15 mM +
EDT 4 mM 0.57 7.23 0.50 2.07 Example 5 TBAI 30 mM +
EDT 8 mM 0.58 11.98 0.50 3.50 Example 6 TBAI 40 mM +
EDT 12 mM 0.59 9.71 0.51 2.99

According to Table 4 and FIG. 7, EDT, TBAI, and a mixed solution thereof were used as a ligand solution, and a mixture of two ligands of various mixing ratios of EDT and TBAI was used to determine optimal ligand mixing conditions .

Table 4 and Figure 7 show device performance parameters obtained using various ligands. According to the results, it was confirmed that Comparative Example 1 using the EDT solution as the ligand solution exhibited a relatively higher Voc value (lower Jsc value) than Comparative Example 2 using the TBAI solution. Conversely, when the TBAI solution was used as the ligand solution, it was confirmed that the exchange device exhibited a higher Jsc value.

In addition, it was confirmed that the inclusion of the mixed ligand showed improved Voc, Jsc and PCE values as compared with the solar cells of Comparative Examples 1 and 2 using a single ligand. At this time, when the ligand mixture of 30 mM TBAI and 8 mM EDT (3.50%) is used, the optimum PCE value is achieved. It was confirmed that the performance of the solar cell was deteriorated in the case of Example 4 and Example 6 in which a mixture having a concentration lower or higher than the optimized concentration was used.

Altering the average concentration of the ligand mixture while maintaining the TBAI / EDT ratio (15/4) results in significantly different device performance (2.07 to 3.50%). The mixing ratio and total concentration affect the performance of the CQD layer. The effect of this concentration is that the surface passivation of the PbS quantum dots can be achieved and the balance between the iodide group of the thiol group or TBAI of the recombinant EDT and the separated acid in oleic acid (OA) after ligand binding The distance between the point and the point is different.

The exchange conditions depend on the time for immersing the spray-treated group CQD layer in the ligand solution. JV characteristics are shown in Fig.

Experimental Example  4. Immersion  Over time Qdot  Performance analysis of solar cell

In order to confirm the performance of the quantum dot solar cell according to the immersion time of the quantum dot semiconductor layer with respect to the ligand solution, Voc, Jsc and FF of the quantum dot solar cells of Examples 7 to 9 were measured in the same manner as in Experimental Example 2 , And the results are shown in Table 5 and FIG.

Dip coating time
(second) Open-circuit voltage
Voc (V) Short circuit current density
Jsc (mAcm ^-2 ) Filling rate
FF (%) PCE (%) Example 7 10 0.50 10.50 0.47 2.49 Example 8 30 0.49 11.62 0.47 2.69 Example 9 50 0.57 11.79 0.60 4.00 Example 10 70 0.58 11.46 0.58 3.85 Example 11 90 0.57 11.34 0.55 3.58

According to Table 5, it was confirmed that acceptable performance was achieved while causing a significant current density after the quantum dot semiconductor layer was exchanged in the ligand solution for 10 seconds. That is, even when immersed in a mixed ligand solution for a very short period of time, a considerable amount of ligand binding is possible and sufficient to exhibit proper cell performance.

In particular, it was found that a negligible current density was observed in a device manufactured using a quantum dot semiconductor layer without a ligand exchange. When a quantum dot semiconductor layer immersed for 50 seconds was used, PCE = 4.00%, V _OC of 0.57 V, J _SC of 11.79 mA cm ^-2 , and FF of 0.60.

From this, it can be seen that the ligand binding process can occur within a very short time, and the resultant degree of ligand exchange has a great influence on the performance of the device. Therefore, it was found that the kind of ligand, the concentration, and the treatment time of the ligand were all important factors for determining the performance of the device.

Experimental Example  5. Quantum dot In the band gap  Following Qdot  Performance analysis of solar cell

In order to confirm the performance of the quantum dot solar cell according to the bandgap range of the quantum dot in the quantum dot solar cell according to the present invention, Voc, Jsc and FF of the quantum dot solar cells of Examples 12 to 14 were measured in Experimental Example 2 And the results are shown in Table 6 and FIG.

Band gap (eV) Open-circuit voltage
Voc (V) Short circuit current density
Jsc (mAcm ^-2 ) Filling rate
FF (%) PCE (%) Example 12 1.61 0.67 9.42 0.49 3.09 Example 13 1.48 0.60 10.66 0.52 3.34 Example 14 1.34 0.53 11.90 0.52 3.30

In Examples 12 to 14, three different quantum dots having band gaps of 1.61 eV, 1.48 eV, and 1.34 eV were used.

According to Table 6 and FIG. 9, it can be seen that the open-circuit voltage (Voc) value decreases as the band gap of the quantum dot decreases, but the short circuit current density (Jsc) value increases. It was also confirmed that the highest PCE was achieved in the device including the quantum dot having the band gap of 1.48 eV.

According to the present invention, a quantum dot semiconductor layer can be formed by applying a quantum dot using a spray method. In this case, the basic characteristics of the quantum dot can be maintained.

Claims (18)

A first step of forming a PbS quantum dot semiconductor layer by spraying a solution containing PbS quantum dots having an average particle diameter of 2 nm to 8 nm and a band gap of 1.0 to 1.9 eV on the electron transport layer at a pressure of 4 to 8 psi;
The PbS quantum dot semiconductor layer is immersed in a ligand solution containing EDT (1,2-Ethanedithiol) and TBAI (tetrabutylammonium iodide) at a molar ratio of 1: 3.5-4.0 for 50 to 90 seconds to bind a ligand on the surface of the PbS quantum dot semiconductor layer Step 2; And
And washing the ligand-bonded PbS quantum dot semiconductor layer.
The method according to claim 1,
Wherein the electron transport layer is an n-type semiconductor including one selected from the group consisting of ZnO, TiO ₂ , SnO ₂ , ITO, and derivatives thereof.
delete delete The method according to claim 1,
The PbS quantum dots included in the solution containing the PbS quantum dots in the first step are selected from the group consisting of oleic acid, oleyl amine, trioctylphosphine oxide and alkyl surfactant Wherein the capping layer is capped with at least one selected acid.


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