KR20190052333A - Conjugated ternary copolymers comprising methylenethiophenecarboxylate and benzodithiophene nd the organic solar cells using them - Google Patents

Abstract

The present invention relates to a conjugated ternary copolymer comprising methylene thiophene carboxylate and benzodithiophene and an organic solar cell using the same. A ternary copolymer according to the present invention contains three monomer elements in one repeating unit constituting a polymer, thereby being able to variously control properties of the polymer than a structure of an existing donor-electron acceptor. Therefore, it is possible to realize a more efficient solar cell device by making an optimized combination with various n-type materials through the same. In addition, since various post-treatments for improving efficiency in an organic solar cell device manufacturing process can be excluded or minimized, it is possible to play a major role in commercialization of the organic solar cell.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conjugated ternary copolymer containing methylene thiophenecarboxylate and benzodithiophene and an organic solar cell using the conjugated ternary copolymers comprising methylenethiophenecarboxylate and benzodithiophene,

TECHNICAL FIELD The present invention relates to a ternary copolymer comprising one electron acceptor or electron donor as one building block, and a ternary copolymer capable of realizing a highly efficient organic solar cell by a simple process and an organic solar cell using the same .

A device that directly produces electricity using a light-absorbing material that generates electrons and holes when light is irradiated is called a solar cell. In 1839, a physicist, Becquerel, in France, first produced a light-induced chemical reaction After the discovery of the photovoltaic phenomenon that led to the generation of photovoltaic phenomena in 1954, the Bell Labs first developed a silicon-based solar cell with an efficiency of about 6%, and conducted research on solar cells centering on inorganic silicon. In 1991, After developing a dye-sensitized solar cell by Rachel's team, researches on solar cells using various organic materials have been actively conducted.

Research on non-fullerene solar cells using various n-type monomers or polymers instead of fullerene, an n-type semiconducting material that has been widely used in organic solar cell research, has been actively conducted recently. The non-fullerene device can extend the absorption wavelength to the visible and near-IR regions and improve the open circuit voltage ( V _oc ) by controlling the energy band gap, rather than the fullerene-based device. As n-type materials are diversified, p-type materials for optimal combination with n-type are also being actively researched and developed.

In order to improve efficiency in various organic solar cell research, it is possible to use two or more solvents in order to dissolve the polymer and the electron acceptor low molecular weight or polymer in the electron active layer during the manufacture of the photoactive layer, or to perform various post- , methanol treatment, etc.) to improve morphology. In addition, an interlayer is inserted to lower the series resistance to optimize the performance of the device.

Such a complicated device fabrication process may be an economical aspect such as the production cost of an organic solar cell or a limit to commercialization.

J. Mater. Chem. A, 2014, 2, 5218-5223 (Apr. 21, 2014)

Accordingly, the present invention intends to provide a new p-type polymer material which is structurally optimized by introducing a terpolymer system and exhibits high efficiency even in a simple process.

The present invention also provides a novel p-type polymer capable of modifying a polymer by introducing a terpolymer system capable of controlling various properties and exhibiting high efficiency as a simple process without complicated manufacturing process, and an organic solar cell using the same. .

In order to solve the above problems, the present invention provides a ternary copolymer comprising a repeating unit selected from the structures represented by the following formula (1).

[Chemical Formula 1]

A detailed description of the structure of the above formula (1) will be described later.

The present invention also provides an organic solar cell comprising the above-mentioned terpolymer as an active layer.

The ternary copolymer according to the present invention contains three monomer elements in one repeating unit constituting the polymer and can control the properties of the polymer more variously than the structure of a conventional donor-electron acceptor .

Further, by controlling the characteristics of the polymer, an optimized combination with various n-type materials can be formed, thereby realizing a more efficient solar cell device.

In addition, various post-treatments for improving the efficiency in an organic solar cell device manufacturing process can be excluded or minimized, which can play a major role in the commercialization of organic solar cells.

1 is a UV-vis absorption spectrum of a ternary copolymer according to an embodiment of the present invention, wherein FIG. 1 (a) is a spectrum in a chlorophyll solution (the illustration is an optical image of a solution) b) is the spectrum in the film.
2 is an energy diagram showing energy levels of a terpolymer (donor) and an ITIC (acceptor) according to an embodiment of the present invention.
Figure 3 shows the results of the performance of the PSC prepared according to the examples and comparative examples of the present invention as a result of (a) the current density-voltage of PSC made from P1 to P5: ITIC (1: 1 wt%) film without solvent additive JV curve, (b) EQE spectrum, (c) JV curve of PSC prepared with mixed film of P1, P5 and ITIC without solvent additive. (d) As a comparative example of the present invention, a PCE value comparison of PSC based on binary mixing and three-way mixing (P1: P5: ITIC) is shown.
4 with respect to PSC (a) according to the present invention is a photoelectric current density (J _ph) versus effective voltage (V _eff) characteristic results, (b) of J PSC in dark conditions is a V curve.
ITIC (b, g), P3: ITIC (c, h), P4: ITIC (a, f) (d, i), P5: ITIC (e, j), (no solvent additive is used in the active layer).
Fig. 6 is a 2D GIWAXD pattern of P1 to P5 and an ITIC mixed film according to the present invention, (b) an out-of-plane profile of the film, and (c) an in-plane profile.
(A, ce) is a ternary copolymer-based PSC (solvent: chlorobenzene) according to the present invention, and (b) (d, g) P3: ITIC and (e, h) P5: ITIC are the PSCs produced by the films annealed at 140 DEG C (0.25% DIO) .
8 (a) shows P3: ITIC (solvent: chlorobenzene), P3: ITIC (containing 140 ° C annealing and 0.25% DIO), and b) is P3: ITIC (DIO or not), and confirming a change in the absorption strength of the film at different wavelengths (623, 697, 626 and 696 nm) for each result, (c) and (d) each J - V characteristics (C) is P3: ITIC (chlorobenzene) (d) P3: ITIC (140 캜 annealing, containing 0.25% DIO)).

Hereinafter, the present invention will be described in more detail.

The present invention relates to a 3-methylthiophenecarboxylate-based ternary copolymer which is excellent in solubility in a conventional solvent using a thiophene structure substituted with a carboxyl group and used as an electron acceptor, As for coalescence,

The present invention relates to a ternary copolymer comprising a repeating unit selected from the structures represented by the following formula (1).

[Chemical Formula 1]

In the above formula (1)

R ₂ is any one selected from the group consisting of hydrogen, deuterium and an alkyl group having 1 to 60 carbon atoms.

Acceptor is any one selected from the following [Structural Formula 1], and Donor is any one selected from the following Structural Formula 2.

[Structural formula 1]

[Structural formula 2]

In the above Structural Formulas 1 to 2,

R is any one selected from hydrogen, heavy hydrogen, and alkyl group having 1 to 60, X is hydrogen (H) or fluorine (F), and Y is S, Se or Te, R ₃ is following [formula 3] Lt; / RTI >

[Structural Formula 3]

In the above formula 3,

-R 'is R, -O-R, -S-R, -Si-RRR, and R is any one selected from hydrogen, deuterium and an alkyl group having 1 to 60 carbon atoms.

n and m are each larger than 0, n + m is 1, and the ratio of monomers in the terpolymerization.

In the above formula 1, the regular regular terpolymer on the left means a polymer structure in which the polymer repeating sequence can be accurately defined by AD-A'-D (or ADA-D '), Regular random terpolymers can predict the polymer structure depending on the monomers, and various known electron donors (D) and acceptor (A) monomers are introduced to diversify the structure of the terpolymer .

The formula (1) according to the present invention may be represented by the following formula (2) as a specific example.

(2)

In the above Formula 2, x is 0.75 and y is 0.25; x is 0.5, y is 0.5, or x is 0.25 and y is 0.75.

The ternary copolymer according to the present invention structurally includes 3-methylthiophenecarboxylate (3MT) in the polymer to induce an asymmetric-random monomer arrangement as described below to have a relatively relatively small crystal form, And has solubility.

The ternary copolymer according to the present invention is characterized in that the monomer is controlled in various ways so that the other electron acceptor or electron acceptor is constituted by a single building block. Specifically, the above formula (2) .

In the above formula 2, 4,8-bis (5- (2-ethylhexyl) thiophen-2-yl) benzo [1,2- b : 4,5- b '] dithiophene (BDT) (2-ethylhexyl) benzo [1,2- c : 4,5- c '] dithiophene-4,8 (3MT) in methylene-3-thiophenecarboxylate -dione (BDD) as a strong electron acceptor unit.

By varying the ratio of the weak electron acceptor 3MT to the strong electron acceptor BDD, various absorption ranges and energy levels from visible light to near infrared rays and a desired energy level can be efficiently realized.

In particular, in the structure of the formula 2 according to the present invention, when x is 0.25 and y is 0.75, a non-fullerene organic solar cell (PSC) is applied using a ternary copolymer corresponding to 0.75 V ( V _oc ) of 17.18 mA / cm 2 and an open circuit current density of 17.18 mA / cm 2, exhibits a high power conversion efficiency of 10.26% and has a long life characteristic.

This is because the highest PCE among the non-fullerene-type PSCs can be obtained without modifying morphology through various post-processes (thermal annealing, solvent vapor annealing, methanol treatment, etc.) .

As described above, another aspect of the present invention relates to an organic solar cell comprising the polymer compound represented by Formula 1 as an active layer.

The organic solar cell according to an embodiment of the present invention may be one in which a substrate, a transparent electrode, a hole transport layer, an active layer, an electron transport layer, and a metal electrode are sequentially laminated. In the organic solar battery according to the present invention, Characterized in that the co-compound is used as the p-type of the active layer.

In general, the organic solar cell according to the present invention can be manufactured by the method described below, but the present invention is not limited thereto.

Generally, it is composed of glass substrate / transparent electrode / hole transporting layer / active layer / electron transporting layer / metal electrode. When the light reaches the active layer through the organic substrate, the transparent electrode and the hole transporting layer, -type Excitons are generated between the polymer materials, electrons move to the metal electrode along the n-type material, and the remaining holes move to the transparent electrode layer through the hole transport layer.

The separated electrons and holes generate current and voltage and generate power. The hole transport layer may typically be composed of PEDOT: PSS [poly (3,4-ethylenedioxythiophene)]: [poly (styrenesulfonate)] and prevents the electrons from migrating to the transparent electrode layer, It helps smooth transportation.

In addition, the active layer should be formed so that the generated excitons can be easily separated into electrons and holes. In the present invention, the active layer is characterized by the active layer, which can be confirmed in Examples described later.

In addition to the glass substrate, the substrate may be a plastic substrate such as PET [poly (ethylene terephthalate)] or PES [poly (isosulfone)].

The active layer using the ternary copolymer compound according to the present invention can be formed into a thin film by a screen printing method, a printing method, a spin casting method, a spin coating method, a dipping method, or an ink jet method.

The metal electrode may be a conductive material, but may be formed of a material selected from the group consisting of Au, Ag, Al, Ni, Cr, and ITO. .

There is no limitation on the transparent electrode, but ITO (indium tin oxide), ZnO (zinc oxide), MnO (manganese oxide) and the like can be used.

Hereinafter, the present invention will be described in more detail with reference to Examples and Experimental Examples. These examples and experimental examples are only intended to illustrate the present invention in detail, and the scope of the present invention is not limited by these examples and experimental examples.

Synthetic example  1 to 3: According to the present invention Samwon  Synthesis of Copolymer

The molecular weight of the synthesized polymer was determined by gel permeation chromatography (GPC) and the redox property of the polymer was measured using cyclic voltammetry (Model: EA161eDAQ). Respectively. As the electrolyte solution, 0.10 M tetrabutylammonium hexafluorophosphate (Bu ₄ NPF ₆ ) in freshly dried acetonitrile was used. Ag / AgCl and Pt wire electrodes were used as the reference electrode and the counter electrode, respectively. The scan speed was 100 mV / s.

[Reaction Scheme 1]

Synthetic example  One : Samwon  Synthesis of Copolymer P2

Monomer 2 (45.0 mg, 0.15 mmol) and monomer 3 (15.0 mg, 0.05 mmol) were dissolved in 20 mL of toluene and 2 mL of dimethylformamide. The resulting solution was stirred for 30 minutes while being replaced with nitrogen. Pd ₂ (dba) ₃ (9.2 mg, 2 mol%) and P (o-tolyl) ₃ (12.2 mg, 8 mol%) were placed in a reactor and heated to 100 ° C and stirred for 24 hours. The reactor was cooled to room temperature, and the reaction was slowly added to methanol to obtain a precipitate, which was purified through sequential extraction with soxhlet through methanol, hexane and chloroform. The final compound was obtained as a dark red solid in 84% yield, and 24.9 kDa PDI 2.69 was confirmed by GPC.

Synthetic example  2 : Samwon  Synthesis of Copolymer P3

1 (181 mg, 0.2 mmol), monomer 2 (30.0 mg, 0.10 mmol) and monomer 3 (77.0 mg, 0.10 mmol) of the above Reaction Scheme 1 were dissolved in 20 mL of toluene and 2 mL of dimethylformamide. The resulting solution was stirred for 30 minutes while being replaced with nitrogen. Pd ₂ (dba) ₃ (9.2 mg, 2 mol%) and P (o-tolyl) ₃ (12.2 mg, 8 mol%) were placed in a reactor and heated to 100 ° C and stirred for 24 hours. The reactor was cooled to room temperature and the reaction was slowly added to methanol to obtain a precipitate, which was then purified by means of soxhlet extraction, successively through methanol, hexane and chloroform. The final compound was obtained in 83% yield with a dark red solid, and 24.4 kDa PDI 3.52 was confirmed by GPC.

Synthetic example  3: Samwon  Synthesis of Copolymer P4

1 (181 mg, 0.2 mmol), monomer 2 (15.0 mg, 0.05 mmol) and monomer 3 (115.0 mg, 0.15 mmol) of the above Reaction Scheme 1 were dissolved in 20 mL of toluene and 2 mL of dimethylformamide. The resulting solution was stirred for 30 minutes while being replaced with nitrogen. Pd ₂ (dba) ₃ (9.2 mg, 2 mol%) and P (o-tolyl) ₃ (12.2 mg, 8 mol%) were placed in a reactor and heated to 100 ° C and stirred for 24 hours. The reactor was cooled to room temperature and the reaction was slowly added to methanol to obtain a precipitate, which was then purified by means of soxhlet extraction, successively through methanol, hexane and chloroform. The final compound was obtained in 86% yield as a dark red solid, and 22.9 kDa PDI 2.84 was confirmed by GPC.

Example  1 to 3: According to the present invention Samwon  Copolymer and ITIC  The non- Plug Manufacture of non-fullerene organic solar cell

A non-fullerene organic solar cell having the following structure and structure was prepared.

(IOP) / indium tin oxide (ITO) / ZnO (30 nm) / terpolymer polymer (P2, P3, P4) according to the present invention: ITIC (85 to 95 nm) / MoO ₃ (10 nm)

[ITIC]

ITO pattern treated with UV-ozone for 20 minutes The ZnO thin film was placed on the glass surface, and the ZnO layer was heat-treated at 200 ° C. for 1 hour. Then, in the absence of the solvent additive, the ternary copolymer polymer And ITIC were spin - coated on the ZnO layer to form the active layer (0.04 ㎠). Thereafter, a 10 nm MoO ₃ layer and a 100 nm Ag layer were formed.

The current density-voltage ( J - V ) characteristics were measured using a Keithley 2400 source meter in illumination of AM 1.5G (100 mW / cm2) supplied by a solar simulator (Oriel, 1000W). The light intensity required was adjusted using an Oriel AM 1.5 air mass filter and, if necessary, a neutral density filter. The incident light intensity irradiated to the PSC was measured with a calibrated broadband optical power meter (Spectra Physics, Model 404).

Example  4 to 9: According to the present invention Samwon  Copolymer and ITIC  The non- Plug Manufacture of non-fullerene organic solar cell

Examples 1 to 3 were prepared in the same manner as in Examples 1 to 3 except that DIO, DPE and the like were added as solvent additives and annealed at various temperature ranges for the active layer.

Examples 1 to 9 are specifically shown in the following [Table 1].

division Solvent Additive Annealing Temp. Example 1 (P2) - Example 4 (P2) - 140 ° C Example 5 (P2) 0.25% DPE 140 ° C Example 2 (P3) - - Example 6 (P3) - 140 ° C Example 7 (P3) 0.25% DIO 140 ° C Example 3 (P4) - - Example 8 (P4) - 140 ° C Example 9 (P4) 0.25% DIO 140 ° C

Experimental Example

(1) The optical properties of the terpolymer synthesized according to the embodiment of the present invention were confirmed. FIG. 1 shows UV-vis absorption spectra in the chloroprene solution and the thin film of the terpolymer according to the embodiment of the present invention to be.

As can be seen in FIG. 1, the ternary copolymers P2 to P4 show that red shift occurs as the charge transporting absorption band (at 523, 559 and 575 nm, respectively) increases as the BDD composition corresponding to the electron acceptance increases And the absorption spectrum of the thin film was more redshift compared to the solution spectrum.

The following Table 2 shows the physical, optical and electrochemical properties of the P1 to P5 polymers according to the present invention, wherein the P1 to P5 polymer thin films have optical bandgaps of 1.98, 1.87, 1.83, 1.82 and 1.80 eV , The optical bandgap gradually decreases as the composition of the BDD unit increases.

That is, it can be seen that in the P1 to P5 polymer, the absorption spectrum range of the terpolymer according to the present invention can be easily controlled by controlling each of the 3MT unit, which is a weak electron acceptor, and the BDD unit, which is a strong electron acceptor.

division M _n
(kDa) PDI Absorption (nm) λ _cut-off
(nm) E _g
(eV) E _ox
(V) Energy levels (eV) solution film HOMO LUMO P1 26.7 2.52 504 539 625 1.98 0.99 -5.42 -3.44 P2 24.9 2.69 523 569 664 1.87 0.95 -5.38 -3.51 P3 24.4 3.52 559 574 677 1.83 0.94 -5.37 -3.54 P4 22.9 2.84 575 616 681 1.82 0.94 -5.37 -3.55 P5 20.5 4.13 613 623 687 1.80 0.91 -5.34 -3.54

M _n : Number average molecular weight

Poly dispersity index (PDI): The polydispersity index

HOMO (highest occupied molecular orbital): highest occupied molecular orbital

LUMO (lowest unoccupied molecular orbital): lowest unoccupied molecular orbital

E _g : energy band gap measured by UV-vis absorption spectrum

E _OX : Onset oxidation potential

(2) The energy diagram of the P1 to P5 polymer is shown in FIG. 2, and the starting oxidation potential (E _OX ) of the P1 to P5 polymer is 0.99, 0.95, 0.94, 0.94 and 0.91 V, and the corresponding HOMO levels are -5.42, -5.38, -5.37, -5.37 and -5.34 eV, respectively. The LUMO levels calculated from the HOMO level and the optical bandgap are -3.44, -3.51, -3.54, -3.55 and 3.54 eV for P1 to P5, respectively.

As the BDD containing repeating group increases, HOMO and LUMO migrate to the upper and lower layers, respectively, thereby correspondingly lowering the bandgap. This shows that it is possible to control the energy level of the polymer by controlling the 3MT and BDD units in the polymer structure and the energy level of the polymer compared with the energy level of ITIC in FIG. It can be seen that strong charge transfer due to light oil flow is possible.

(3) The performance of the ternary copolymer according to the present invention of Examples 1 to 9 and the non-fullerene organic solar cell using ITIC is shown in Table 3 below.

division Solvent Additive Annealing
Temp. V _oc
(V) J _sc
(mA / cm 2) FF
(%) PCE
(%) Example 1 (P2) - 0.95 15.76 59.76 8.95 Example 4 (P2) - 140 ° C 0.94 16.09 63.28 9.57 Example 5 (P2) 0.25% DPE 140 ° C 0.93 16.25 63.66 9.62 Example 2 (P3) - - 0.94 17.18 63.52 10.26 Example 6 (P3) - 140 ° C 0.91 17.49 66.53 10.59 Example 7 (P3) 0.25% DIO 140 ° C 0.92 17.22 69.56 11.02 Example 3 (P4) - - 0.90 17.19 61.77 9.56 Example 8 (P4) - 140 ° C 0.89 15.93 67.63 9.59 Example 9 (P4) 0.25% DIO 140 ° C 0.87 16.52 62.07 8.92

The simple PSCs (Examples 1 to 3) based on the ternary copolymer according to the present invention exhibited a relatively high open circuit voltage ( V _oc ) of 0.9 mA or more and an open circuit current density ( J _sc ) of 15 mA / cm 2 or more, respectively , And as the composition of the BDD unit increased, V _oc gradually decreased from 0.95 V to 0.90 V, which was in good agreement with the difference between the HOMO level of the polymer and the LUMO level of ITIC as shown in FIG. 2, The simple PSC based on P2 to P4 showed a PCE value of 8.95 to 10.26%.

Particularly, in Example 2 (P3: ITIC, 1: 1 wt%), PSC prepared without a solvent additive or a separate heat treatment process had a high V _oc of 0.94 V and a J _sc of 17.18 mA / High PCE, which is the highest reported value for a specific interlayer structure and non-fullerene organic solar cell without heat treatment and without addition of solvent additive.

As a comparative example of the organic solar cell device according to the present invention, a PSC based on a three-way mixed (P1: P5: ITIC) film in which the weight ratio of P1 and P5 is different from that of the ternary copolymer structure according to the present invention As shown in FIGS. 3 (c) and 3 (d), the performance was relatively poor.

As can be seen from these results, due to the synergistic effect of the third monomer unit (for example, BDD), the device using the ternary copolymer according to the present invention is superior to the device using the ternary mixture having P1 and P5 Performance is outstanding.

Next, the performance of the P3-based PSC using the annealed active layer and the solvent additive of DIO was investigated. As a result, a PCE value of up to 11% was obtained by P3: ITIC of 0.25% DIO and 10 minutes of thermal annealing at 140 ° C And P2O: ITIC and P4: ITIC showed PCE of 9.62% and 9.56% at 0.25 wt% DIO at 140 DEG C, respectively (see Table 3 above). That is, under the same process conditions, the P3 terpolymer was found to be the most excellent.

In addition, the PSC (P3: ITIC-based PSC) according to Example 2 of the present invention can be confirmed to have similar performance levels in comparison with the presence or absence of additives, the post-annealing treatment for the active layer, and the use of a specific intermediate layer. This means that the present invention provides various advantages such as simplification of PSC manufacturing process, excellent reproducibility and shortening of manufacturing time.

(4) Ternary copolymer according to the present invention: The external quantum efficiency (EQE) spectrum of the ITIC-based PSC is shown in FIG. 3 (b).

All devices exhibited high EQE from visible to near-infrared wavelengths, and the active layer efficiently generated excitons. In addition, the high EQE values in the range of 500 to 700 nm are due to both the terpolymer and ITIC according to the present invention, and in particular, the larger bandgap and the middle bandgap monomer segment are combined into a donor, Enhanced EQE values at about 500-700 nm due to the behavior were identified.

Therefore, since the wavelength range of 500 to 700 nm is strongest in the solar emission spectrum, it is very advantageous to accurately improve light harvesting characteristics.

5 to FIG. 4 is (a) shows the photocurrent density (J _ph) versus effective voltage (V _eff) characteristics result with respect to the PSC in accordance with the present invention, (b) and the JV curve of the PSC in the dark condition, the maximum exciton The generation rate G _max is determined as the photocurrent density Jph in accordance with the change of the effective voltage V _eff . G _max The value is calculated by the equation J _sat = q L G _max , where J _sat is the saturated photocurrent density, q is the electron charge, and L is the thickness of the active layer of the PSC.

P3 according to the invention: G _max and J _sat value of ITIC based PSC can be seen that higher than G _max, and J _sat value of another PSC, which low level of charge recombination is because, excellent by generating more free charge carriers Exciton dissociation efficiency and charge carrier formation.

ITIC (b, g) and P3: ITIC (c, h) are the AFM and TEM images of the terpolymer of ITIC film according to the present invention, ), P4: ITIC (d, i), P5: ITIC (e, j) (no solvent additive is used in the active layer).

As shown in FIG. 5, it can be seen that all of the active layers made of the terpolymer: ITIC (1: 1) blend are very fine, having an average square root roughness less than 0.4 nm relative to P5: ITIC. This means that the random terpolymers according to the present invention interfere with the regular arrangement of the polymer backbone, thereby relaxing the degree of crystallization of the polymer backbone, so that ITIC can be easily inserted into the network of polymer chains.

Also, in the TEM image, it can be confirmed that the PSC produced from the terpolymer as in the present invention exhibits excellent performance as compared with P1 and P5.

Compared with the blend films containing P1 and P5, the internal form of the P3: ITIC blend film is much more uniform and has a nano-sized crystal structure, which is an effective charge transport channel and can be used for efficient exciton diffusion, charge separation and transport .

Therefore, PSC performance can be further improved by using a terpolymer having an optimum crystallinity more than P1 and P5.

(7) Grazing incidence wide-angle X-ray scattering (GIWAXS) was performed on the terpolymer: ITIC film in order to confirm the relation between the photocell performance and the polymer chain arrangement. (A) a 2D GIWAXD pattern of P1 to P5 and an ITIC mixed film according to the present invention, (b) an out-of-plane profile of the film, and (c) an in-plane profile.

It can be seen that all the P1 to P5 polymers have a (010)? Stacking peak in the out-of-plane direction and a (100) diffraction in the frontal direction in the in-plane direction. Further, the half width (FWHM) of the (100) diffraction peak in the in-plane direction decreases gradually as the content of the 3MT portion decreases. That is, introducing a 3MT moiety that is randomly bonded to a donor disturbs the chain regularity and reduces the aligned domains in the film. Also, it can be seen that increasing the composition of the BDD unit promotes the rigidity and packing behavior and promotes the crystallization of the polymer chain.

The P2 to P4 and ITIC blend films exhibit strong (010) diffraction of pi-pi stacking in the out-of-plane profile, as in Fig. In addition, the diffraction behavior of the terpolymer showed a vertical direction facing on the substrate similar to the diffraction results of the P1 and P5 blend films, which is advantageous for vertically transporting the charge carriers in the sandwich PSC.

In addition, it can be seen that P3: ITIC film has the smallest crystal aggregation length of 45.75 Å, and P3: ITIC is the optimal form with nano-phase separation. In this GIWAXD result, The tendency to have a small crystal size in vertical directionality and in mixing with ITIC makes it possible to implement a high performance PSC.

FIG. 7 is a graph showing the results of the measurement of the PSC performance stability (maximum 1000 hours or more) and the AFM image according to the present invention, in which (a, ce) (D, g) P3: ITIC and (c, f) are PSC (chlorobenzene), (b, fh) (e, h) P5: ITIC.

 P1 ~ P5: The PCE of the PSC with ITIC active layer thin film maintained 96.5% of the initial value for a maximum of 1000 hours or more, whereas the stability of operation was reduced by 16% when the DIO additive was used. In addition, it was confirmed that the active layer containing the DIO additive produced many micrometer scale aggregates after 1000 hours, whereas when the DIO additive was not used, the uniform form was maintained and the aggregate was formed even after 1,000 hours at atmospheric conditions It was not.

In order to confirm the operational stability of the P3: ITIC PSC to which the DIO was added, the PSC apparatus was maintained in a state of continuous illumination (AM 1.5 G 100 mW / cm 2 illumination) and the performance was periodically measured. As a result, As can be seen, performance of all devices decreases with increasing illumination / operating time, but P3: ITIC based PSCs without DIO exhibit better stability.

As shown in FIG. 8 (b), the absorption intensity of the P3: ITIC film containing 0.25% DIO was lower than that of the initial absorption intensity P3 (at 626 nm) and ITIC (at 696 nm) . This is because the decomposition of the conjugated ring structure occurs easily in both P3 and ITIC by reducing with DIO additive.

Also, AFM measurements for comparison with morphological changes before and after continuous illumination show that the DIO mixed film produces many micrometer-scale aggregates after 1 hour of illumination, while the DIO mixed film produces homogeneous forms , And no agglomerate was observed even after 1 hour of illumination. From these results, it can be understood that the operating stability of P3: ITIC according to the present invention is very excellent and is due to the light stability.

As described above, the ternary copolymer derivative according to the present invention is characterized in that it is based on BDT, 3MT and BDD, and by adding 3MT and BDD monomers to the polymer structure and controlling the amount thereof, the optical and electrochemical characteristics can be effectively Control, and realize excellent electrochemical characteristics.

In particular, the film of P3: ITIC (1: 1 wt%) exhibits a high PCE of 10.26% with a high V _oc of 0.95 V and a J _sc of 17.18 mA / cm 2 in the PSC, Fullerene PSCs made with < RTI ID = 0.0 > PTB7-Th: ITIC < / RTI > based PSCs. In addition, the ternary copolymer derivative-based PSC device according to the present invention exhibits excellent long-life characteristics for 1100 hours, and is excellent in operational stability, and can realize a PSC having high stability and excellent efficiency with low cost and simple process according to the present invention .

Claims (3)

1. A ternary copolymer comprising a repeating unit selected from the following structures represented by the following formula (1)
[Chemical Formula 1]

R ₂ is any one selected from the group consisting of hydrogen, deuterium and an alkyl group having 1 to 60 carbon atoms, Acceptor is any one selected from the following Structural Formula 1, Donor is selected from the following Structural Formula 2 Lt; / RTI >
[Structural formula 1]

[Structural formula 2]

R is any one selected from the group consisting of hydrogen, deuterium, and alkyl groups having 1 to 60 carbon atoms; X is hydrogen (H) or fluorine (F); Y is S, Se Or Te, and R < ₃ > is any one selected from the following [formula 3]
[Structural Formula 3]

In the above structural formula 3, -R 'is any one selected from the group consisting of R, -OR, -SR, -Si-RRR, R is hydrogen, deuterium and an alkyl group having 1 to 60 carbon atoms,
n and m are each larger than 0, and n + m is 1. The method according to claim 1,
The ternary copolymer represented by the formula (1) is represented by the following formula (2)
(2)

In the above Formula 2, x is 0.75 and y is 0.25; x is 0.5, y is 0.5; x is 0.25, y is 0.75, or x is 0.25 and y is 0.75. An organic solar cell comprising the ternary copolymer according to claim 1 as an active layer.

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