KR102186732B1 - Electron transport material and organic photoelectric device using the same - Google Patents

Abstract

The present invention relates to an electron transport material which is easy to transport electrons and exhibits stable light emission in an organic photoelectric element to be usefully used as an element for flat panel and plastic displays, and the organic photoelectric element using the same. To this end, the organic photoelectric element comprises a substrate, a pair of electrodes, and an organic thin film layer.

Description

Electron transport material and organic photoelectric device using the same {ELECTRON TRANSPORT MATERIAL AND ORGANIC PHOTOELECTRIC DEVICE USING THE SAME}

The present invention relates to an electron transport material and an organic photoelectric device using the same, and more particularly, it includes discotic and rod-shaped p and n-type derivatives capable of maximizing intermolecular interaction, and is dissolved in an alcohol solvent in the main chain. It relates to an alcohol-soluble electron transport material for an organic photoelectric device having an amine group structure and an organic photoelectric device using the same.

In recent years, research on displays has been actively conducted, and among them, organic light-emitting diodes (OLEDs) have attracted the most attention. Compared to conventional liquid crystal displays (LCDs) or cathode ray tubes (CRT), OLEDs do not require a backlight because they are self-luminous, and are superior in wide viewing angles, power consumption, and contrast ratio. It has features and has the advantage that it can be manufactured in an ultra-lightweight and ultra-thin type.

In addition, on the contrary, in the organic photovoltaic (OPV) phenomenon, photons are separated into electrons and holes in the organic active layer receiving sunlight to form excitons, which form an electron donor and receive electrons. (acceptor) It moves to the interface of the material, and is separated by the difference in the level of each LUMO (Lowest Unoccupied Molecular Orbit) to produce electricity.

A deposition process and a solution process are possible for such a conductive organic material, and a deposition process is possible mainly for a small molecule, and a solution process is possible for an oligomer and a polymer. In the case of the evaporation process, vacuum is essential, so it has disadvantages that it is difficult to increase process cost, large area, and flexibility. On the other hand, the solution process does not require a vacuum, so the process cost can be lowered, and it has the advantage of enabling a large area and flexibility.

In order to implement such a solution process capable of polymer and oligomer light emitting devices, many studies are being conducted, and in particular, research and development of a polymer electron transport layer capable of a solution process that does not affect the morphology of the light emitting layer (Adv. Mater. 2007, 19) , 2010-2014), but currently shows lower efficiency than OLED devices by the deposition process. This is because various electron transport layers and hole transport layers are introduced through the deposition process. In particular, polymers do not have good solubility in alcohols due to the solid main chain of the polymer. In addition, the polymer has a disadvantage that it is difficult to purify.

Accordingly, it is required to develop an organic electron transport material capable of a solution process while having excellent electron injection and mobility.

[Patent Document 1] Korean Patent Registration Publication No. 10-1334204 [Patent Document 2] Japanese Patent Registration Publication No. 4188401 [Patent Document 3] Japanese Patent Publication No. 2015-170793

[Non-Patent Document 1] Adv. Mater. 2007, 19, 2010-2014 [Non-Patent Document 2] Li, et al., Amino-functionalized conjugated polymer electron transport layers enhance the UV-photostability of planar heterojunction perovskite solar cells, Chem. Sci. , 2017, 8, 4587

Therefore, the object of the present invention is to solve the problems of the prior art, by introducing a functional group having a high solubility in alcohols to various p-type or n-type derivatives, it is possible to maximize the interaction between molecules and effective electron transport. It is to provide an alcohol-soluble electron transport material for an organic photoelectric device and an organic photoelectric device using the same.

In addition, it is an object of the present invention to provide an alcohol-soluble electron transport material for an organic photoelectric device that is capable of a solution process and is easy to purify in order to solve the difficulty of polymer purification, and an organic photoelectric device of high efficiency and long life using the same.

In order to achieve the above object, the electron transport material according to an embodiment of the present invention may be represented by the following formula (I):

[Formula I]

The organic photoelectric device according to an embodiment of the present invention may include the electron transport material described above.

An organic photoelectric device according to another embodiment of the present invention includes a substrate; A pair of electrodes comprising an anode and a cathode on the substrate; And an organic thin film layer disposed between the anode and the cathode and including the electron transport material.

The organic thin film layer may include at least one of a light emitting layer, an electron transport layer, an electron injection layer, a hole transport layer, or a hole injection layer.

The anode may include a material selected from the group consisting of indium tin oxide, zinc oxide, indium oxide, indium zinc oxide, conductive polymer, and combinations thereof.

The positive electrode may be a polythiophene-based conductive polymer coated on indium tin oxide.

The negative electrode may include a material selected from the group consisting of aluminum, magnesium, calcium, sodium, potassium, titanium, and combinations thereof.

The electron transport material according to the present invention has a p-type derivative or n-type derivative having a disk-shaped or rod-shaped structure as a main chain, and an amine group is introduced into a side branch to improve solubility in an alcohol-based solvent, and thus can be effectively applied to a solution process, The interaction between molecules is maximized, making it easy to transport electrons.

In addition, the electron transport material according to the present invention exhibits stable light emission in the OLED device and has excellent luminous efficiency, and thus can be usefully used as a device for flat panel and plastic displays.

In addition, the electron transport material according to the present invention exhibits high efficiency by effectively collecting charge and lowering the surface resistance in OPV (organic solar cells) devices, which is the opposite principle of OLED (Organic Light Emitting Diodes) devices, and is usefully used as a next-generation energy source. Can be.

The effects of the present invention are not limited to the effects mentioned above, and other effects that are not mentioned will be clearly understood by those skilled in the art from the description of the claims.

1 is a graph showing an H-NMR spectrum of an organic electron transport material of an example.
2 shows UV absorption spectrum data for a solution of an organic electron transport material according to an embodiment and a film formed using the solution.
3 is a graph compared to ferrocene by evaluating the electrochemical properties of the organic electron transport material compound of the example.
FIG. 4 is data obtained by measuring an organic electron transport material according to an embodiment in a vertical (out-of-plane) and horizontal (in-plane) direction by GIXRD (Grazing Incidence X-ray Diffraction).
5 is an IV curve of the organic photoelectric devices of Preparation Example and Comparative Preparation Example.
6 is a graph showing the aging stability of the organic photoelectric devices of Preparation Example and Comparative Preparation Example.

Advantages and features of the present invention, and a method of achieving them will become apparent with reference to specific examples described below in detail together with the accompanying drawings. However, the present invention is not limited to the specific examples disclosed below, but may be implemented in a variety of different forms, and only the specific examples of the present invention make the disclosure of the present invention complete, and are generally in the technical field to which the present invention belongs. It is provided to completely inform the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims.

Unless otherwise defined, all terms (including technical and scientific terms) used in the present specification may be used as meanings that can be commonly understood by those of ordinary skill in the art to which the present invention belongs. In addition, terms defined in a commonly used dictionary are not interpreted ideally or excessively unless explicitly defined specifically.

Hereinafter, the electron transport material of the present invention will be described in detail.

The electron transport material according to the present invention may be an organic electric field monomolecule in which an amine group is introduced with a p-type or n-type derivative having electronic properties as a main chain. In the present invention, the electronic property refers to a property that has a conduction property along the LUMO level to facilitate injection of electrons formed at the cathode into the emission layer and movement in the emission layer.

Specifically, the electron transport material may be represented by the following formula (I):

[Formula I]

In addition, the compound represented by Formula I (hereinafter, also abbreviated as'QTA') may be prepared, for example, by the following reaction scheme.

[Scheme I]

The organic electron transport material represented by Formula I can have luminescence properties, electronic properties, and thermal stability, and can have good solubility in alcohols, so that it can be easily applied to a solution process, so that polymer purification is easy, By improving the interaction between molecules, the efficiency of electron transport can be increased.

The organic photoelectric device according to the present invention may include the organic electron transport material described above.

The organic photoelectric device may include a substrate, an electrode, and an organic thin film layer including the electron transport material. Specifically, it may have a structure of a substrate, a pair of electrodes including an anode and a cathode on the substrate, and an organic thin film layer positioned between the anode and the cathode.

The positive electrode may be indium tin oxide, zinc oxide, indium oxide, indium zinc oxide, or a conductive polymer, and may be used in combination of two or more, but is not limited thereto. Preferably, the positive electrode may be a polythiophene-based conductive polymer coated on indium tin oxide.

The polythiophene-based conductive polymer may be PEDOT (poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) or PEDOT:PSS(poly(styrenesulfonate))), more preferably PEDOT: It can be PSS.

The negative electrode may be aluminum, magnesium, calcium, sodium, potassium, or titanium, and in some cases, two or more types may be mixed and used, but the present invention is not limited thereto. Preferably, it is effective to use aluminum as the cathode.

The organic thin film layer may include one or more layers, preferably at least one of a light emitting layer, an electron transport layer, an electron injection layer, a hole transport layer, or a hole injection layer. Each of the organic thin film layers may include the electron transport material described above, and the light emitting layer and the electron transport layer may simultaneously contain the electron transport material.

Hereinafter, the following examples are exemplarily presented to demonstrate the excellent effects of the organic electron transport material and the organic photoelectric device according to the present invention, but the present invention is not limited thereto.

Examples and Comparative Examples

Example

Preparation of electron transport materials

A method of preparing an electron transport material of Formula I is described according to the following scheme.

[Scheme 1]

[Formula I]

Step 1: Synthesis of Compound M1

In a nitrogen atmosphere, 4-bromophenol (Aldrich) 10g, 3-dimethylaminopropylchloride hydrochloride (99%, Acros) 27.4g, potassium carbonate (K ₂ CO ₃ ) 23.9 g was added to 90 mL of dimethylformamide (DMF), and stirred at 90° C. for 48 hours. After the reaction was completed, the mixture was washed with water and purified by column with chloroform to give 6.1 g of compound M1 (yield 40.8%).

Step 2: Synthesis of Compound M2

In a nitrogen atmosphere, 3 g of Compound A was dissolved in 30 ml of dried THF, the temperature was lowered to -78°C, and 2.2 equivalents of normal butyl lithium (n-BuLi, Aldrich) was slowly added. The reaction mixture was stirred at -78°C for 2 hours, and then 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (2-Isopropoxy-4,4, 5,5-tetramethyl-1,3,2-dioxaborolane, Aldrich) was added, and after stirring at -78°C for 2 hours, the mixture was stirred for 24 hours while gradually increasing the temperature to room temperature. When the reaction was completed, organic matter was extracted with chloroform, washed with water, and purified by column to give 1.6 g of compound M2 (yield 45.0%).

Step 3: Synthesis of the compound of formula I

After dissolving 0.3 g of compound M2 and 0.3 g of compound M3 obtained above in 20 ml of 1,4-dioxane (1,4-dioxane, Aldrich), it is completely dissolved by stirring, and then tetrakis (triphenylphosphine) palladium (tetrakistriphenyl) After adding and stirring 0.07 g of phosphinepalladium (0), Aldrich), 15 ml of 2 mol potassium carbonate (K ₂ CO ₃ , Aldrich) aqueous solution was added and stirred at 90° C. for 48 hours. When the reaction was completed, extraction was performed with chloroform, followed by column purification, to obtain 0.31 g (yield 84%) of the compound of Formula I (QTA).

¹ H-NMR and UV absorption spectra of the organic electron transport material compound obtained in the above example are shown in FIGS. 1 and 2.

1 is a graph showing the ¹ H-NMR spectrum of the organic electron transport material compound of the above example. From the ¹ H-NMR spectrum of FIG. 1, it was confirmed that the desired final compound (QTA) was successfully synthesized.

2 is a graph showing the UV spectrum of a QTA solution of the organic electron transport material compound (QTA) of the above embodiment and a film formed using the same. As shown in FIG. 2, in the case of the UV spectrum of the compound (QTA) on the film, it appeared to be red-shifted compared to the solution, which is due to dense stacking between molecules.

In addition, the electrochemical properties of the organic electron transport material compound (QTA) of the example are shown in FIG. 3 in comparison with ferrocene.

As shown in FIG. 3, the organic electron transport material compound (QTA) of the example exhibits a HOMO level of -5.15 eV and an LUMO level of -2.80 eV, confirming that it can be used as a hole injection layer due to an appropriate HOMO level. Became.

Comparative example

After adding 100 g of 3,3"'-dihexyl-2,2':5',2":5",2'"-quaterthiophene to the flask, purging with nitrogen, 13 mL of tetrahydrofuran was added to -78℃ Cooled to. 37 mL (concentration 164 mol/L) of n-butyllithium n-hexane solution was added dropwise thereto, followed by stirring for 30 minutes. And further, after adding 22 mL of tributylchlorostanan dropwise thereto, the temperature was raised to room temperature and stirred for 3 hours. After stirring, ion-exchanged water and n-hexane were added for liquid separation, and the obtained organic layer was further washed twice with ion-exchanged water, and then dried over sodium sulfate. Then, by distilling off the solvent (3,3"'-dihexyl-[2,2':5',2":5",2'"-quaterthiophene]-5,5'"-diyl) A mixture (345 g) containing bis (tributylstanan) was obtained.

Next, in a separate flask, 30 g of the mixture obtained above and 1.2 g of 4-bromo-N,N-diphenylaniline were added, and after nitrogen substitution, 45 mL of toluene and 0.10 g of tetrakis (triphenylphosphine) palladium were added. It was added sequentially and stirred under reflux conditions for 8 hours.

After stirring, the mixture was allowed to stand to cool to room temperature, chloroform and ion-exchanged water were added thereto for liquid separation, and the obtained organic layer was further washed with ion-exchanged water and dried over sodium sulfate. Then, the solvent was distilled off and purified by column chromatography to obtain a compound of the following formula II (hereinafter, also abbreviated as'QTP') (amount: 076 g, yield: 44%, total yield in two steps)

[Chemical Formula Ⅱ]

¹ shows the measurement result of H-NMR are shown below.

¹ H-NMR(CDCl3):δ 744 (4H, d, J=89Hz), 728-723 (m,8H), 712-710 (m,10H), 706-700 (m,12H), 278 (t ,J=74Hz, 4H), 169(quint, J=74Hz, 4H), 144-130(m,12H), 089(m,6H)

Solubility experiment

Solubility tests of the compounds synthesized in Examples and Comparative Examples in alcohol-based solvents were conducted. 1 mg of each compound was dissolved in a solvent of 1.5 ml of methanol + 5 µl of acetic acid. As a result, it was confirmed that the compound of Example was easily dissolved without any special temperature treatment, but the compound of Comparative Example was not dissolved at all.

[ Organic photoelectric device Manufacture of]

Manufacturing Example 1

An organic photoelectric device was fabricated under the following conditions using the organic electron transport material compound (QTA) synthesized in the above example.

PEDOT:PSS was filtered using a 0.45㎛ PTFE syringe filter, and stirred in a shaker to prevent phase separation of PEDOT and PSS. Poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl][3-fluoro-2-[ (2-ethylhexyl)carbonyl] thieno[3,4-b]thiophendiyl]] (hereinafter referred to as'PTB7') and [6,6]-phenyl C ₇₁ butyric acid methyl ester (hereinafter referred to as'PC ₇₁ BM ') mixture (PTB7:PC ₇₁ BM=1:1.5 weight ratio) was dissolved in chlorobenzene at a concentration of 0.5wt%, stirred for 24 hours, and filtered using a 5 μm PTFE syringe filter. The prepared ITO substrate and samples were transferred to a glove box, and each was spin coated. After each spin coating, PEDOT:PSS was heat-treated at about 110°C for about 20 minutes, PTB7:PC ₇₁ BM was heat treated at room temperature for about 1 hour to remove residual solvent, and the organic electron transport material compound synthesized in the above example A methanol (MeOH) solution (10 ^-4 M) of (QTA) was spin-coated and heat-treated at room temperature for 1 hour to remove the residual solvent, and thin films on the electrode portion excluding the photoelectric conversion surface were removed. To deposit the electrode material, it was transferred to a high vacuum chamber (1×10 ^-6 torr or less) of a thermal evaporator, and electrodes were formed in the order of aluminum (Al) (5Å/s, 200nm), and ITO/PEDOT: An organic photoelectric device having a structure of PSS/PTB7:PC ₇₁ BM/QTA/Al was manufactured.

Comparative Preparation Example 1

An organic photoelectric device having a structure of ITO/PEDOT:PSS/PTB7:PC ₇₁ BM/Al was manufactured in the same manner as in Preparation Example 1, except that the QTA solution was not used.

Manufacturing Example 2

Poly[[4,8-bis[5-(2-ethylhexyl)-2-thienyl]benzo[1,2-b:4,5-b′]dithiophene instead of the mixture of PTB7 and PC ₇₁ BM -2,6-diyl]-2,5-thiophendiyll[5,7-bis(2-ethylhexyl)-4,8-dioxo-4H,8H-benzo[1,2-c:4, 5-c']dithiophene-1,3-diyl]] (hereinafter referred to as'PBDB-T') and 2,2'-[[6,6,12,12-tetrakis(4-hexylphenyl)- 6,12-dihydrodithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b′]dithiophene-2,8 -Diyl]bis[methylidine (3-oxo-1H-indene-2,1(3H)-diylidene)]]bis[propanedinnitrile] (hereinafter,'ITIC') mixture (PBDB-T:ITIC =1: 1 weight ratio) was carried out in the same manner as in Preparation Example 1, and an organic photoelectric device having a structure of ITO/PEDOT:PSS/PBDB-T:ITIC/QTA/Al was manufactured.

Comparative Preparation Example 2

An organic photoelectric device having a structure of ITO/PEDOT:PSS/PBDB-T:ITIC/Al was manufactured in the same manner as in Preparation Example 2, except that the QTA solution was not used.

Comparative Preparation Example 3

PFN(poly[(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-di An organic photoelectric device having a structure of ITO/PEDOT:PSS/PTB7:PC ₇₁ BM/PFN/Al was manufactured in the same manner as in Preparation Example 1, except that a solution of octylfluorene)]) was used.

Comparative Preparation Example 4

An organic photoelectric device having a structure of ITO/PEDOT:PSS/PTB7:PC ₇₁ BM/MeOH/Al was manufactured in the same manner as in Preparation Example 1, except that only a methanol solvent was used instead of the QTA solution.

Manufacturing Example 3

The prepared ITO substrate and zinc oxide were transferred to a glove box, and spin-coated. Then, a methanol (MeOH) solution (10 ^-4 M) of the organic electron transport material compound (QTA) synthesized in the above example was spin-coated and heat-treated at room temperature for 1 hour to remove the residual solvent. Subsequently, a mixture of PBDB-T and ITIC (PBDB-T:ITIC=1:1 weight ratio) was dissolved in chlorobenzene at a concentration of 0.5 wt%, stirred for 24 hours, and filtered using a 5 μm PTFE syringe filter. , After spin coating the mixture on the QTA layer, heat treatment at room temperature for 1 hour to remove residual solvent, molybdenum oxide (MoO ₃ ) was laminated thereon, and thin films of the electrode portion excluding the photoelectric conversion surface were erased. . In order to deposit the electrode material, it was transferred to a high vacuum chamber (1×10 ^-6 torr or less) of a thermal evaporator, and electrodes were formed in the order of silver (Ag) (5Å/s, 200nm), and ITO/ZnO/ An organic photoelectric device having a structure of QTA/PBDB-T:ITIC/MoO ₃ /Ag was manufactured.

Comparative Production Example 5

An organic photoelectric device having a structure of ITO/ZnO/PBDB-T:ITIC/MoO ₃ /Ag was manufactured in the same manner as in Preparation Example 3 except that the QTA solution was not used.

Comparative Production Example 6

In the same manner as in Preparation Example 1, except that the solution of the compound (QTP) prepared in Comparative Example was used instead of the solution of QTA, ITO/PEDOT:PSS/PTB7:PC ₇₁ BM/QTP/Al An organic photoelectric device was fabricated.

The open circuit voltage (Voc), short time current (Jsc), fill factor (FF), and power conversion efficiency of the organic photoelectric device manufactured in Preparation Example and Comparative Preparation Examples efficiency), surface resistance, and resistivity were measured, respectively, and are shown in Table 1 below.

Voc(V) Jsc(mA/cm ² ) FF(%) PCEave(%) PCEmax(%) Rs(Ω/cm ² ) Rsh(Ω/cm ² ) Manufacturing Example 1
(QTA/Al) 0.69 13.4 71.8 7.2 7.2 2.5 1307 Comparative Preparation Example 1
(Al) 0.53 13.3 60.8 4.7 4.7 4.0 702 Manufacturing Example 2
(QTA/Al ^a ) 0.85 15.5 62.9 8.3 8.4 7.2 1291 Comparative Preparation Example 2
(Al ^a ) 0.61 15.1 52.3 4.8 4.9 10.6 594 Comparative Preparation Example 3
(PFN/Al) 0.85 15.6 59.7 8.0 8.0 8.3 620 Comparative Preparation Example 4
(MeOH/Al) 0.61 15.1 55.1 5.0 5.1 8.4 421 Manufacturing Example 3
(ZnO/QTA) 0.87 15.1 67.5 9.0 9.0 6.4 1210 Comparative Production Example 5
(ZnO) 0.89 16.4 55.5 8.1 8.2 9.9 532 Comparative Production Example 6
(QTP/Al) 0.85 15.3 55.1 7.5 7.5 10.3 700

delete

As described above, the organic photoelectric devices according to Preparation Examples 1 to 3 have excellent effects in all of the open-circuit voltage, short-circuit current, fill factor, power conversion efficiency, surface resistance and resistivity compared to the organic photoelectric devices according to Comparative Preparation Examples 1 to 6 You can see that there is.

In addition, as shown in FIG. 5, it can be seen that the efficiency of the organic photoelectric device (QTA/Al) of Preparation Example 1 is increased up to 71% compared to the organic photoelectric device of Comparative Preparation Example 1 (Al).

In addition, FIG. 6 shows the power conversion efficiency of Comparative Preparation Example 1 (Al), Comparative Preparation Example 3 (PFN/Al), and Preparation Example 1 (QTA/Al), and only in the case of Preparation Example 1, the stability over time of the device is You can see that it is excellent.

Claims (7)

Electron transport material represented by the following formula (I):
[Formula I]

An organic photoelectric device comprising the electron transport material according to claim 1. The method of claim 2,
The organic photoelectric device,
Board;
A pair of electrodes comprising an anode and a cathode on the substrate; And
An organic photoelectric device comprising an organic thin film layer disposed between the anode and the cathode and comprising the electron transport material according to claim 1. The method of claim 3,
The organic thin film layer includes at least one of a light emitting layer, an electron transport layer, an electron injection layer, a hole transport layer, or a hole injection layer. The method of claim 3,
The anode is an organic photoelectric device comprising a material selected from the group consisting of indium tin oxide, zinc oxide, indium oxide, indium zinc oxide, conductive polymer, and combinations thereof. The method of claim 5,
The anode is an organic photoelectric device in which a polythiophene-based conductive polymer is coated on indium tin oxide. The method of claim 3,
The cathode is an organic photoelectric device comprising a material selected from the group consisting of aluminum, magnesium, calcium, sodium, potassium, titanium, and combinations thereof.

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