KR101680555B1 - Polymer solar cell including rod-g-coil copolymer compatibilizer - Google Patents

Abstract

The present invention relates to a polymer solar cell comprising a rod-coil junction copolymer compatibilizer, and more particularly to a polymer solar cell comprising an active layer having a bulk heterojunction structure of a polymer and a fullerene derivative. The battery according to any one of claims 1 to 3, wherein the polymer comprises a copolymer in which a first polymer in which an alkyl group is attached to the active layer is polymerized with a first polymer and a second polymer in which a supramolecular interaction between the fullerene derivative and the second polymer is conjugated, .
The present invention comprises an active layer including a bulk heterojunction structure of an electron acceptor region including an electron donor region including a polymer and a fullerene derivative, The active layer may include a first polymer obtained by polymerizing a conductive polymer having an alkyl group attached thereto; And a second polymer that is grafted to one or more monomers of the first polymer to form a copolymer, wherein the second polymer comprises the fullerene derivative and the supramolecule A polymer solar cell capable of forming a supramolecular interaction.

Description

Polymer solar cells including rod-g-coil copolymer compatibilizer including rod-coil junction copolymer compatibilizer [

The present invention relates to a polymer solar cell comprising a rod-coil junction copolymer compatibilizer, and more particularly to a polymer solar cell comprising an active layer having a bulk heterojunction structure of a polymer and a fullerene derivative. The battery according to any one of claims 1 to 3, wherein the polymer comprises a copolymer in which a first polymer in which an alkyl group is attached to the active layer is polymerized with a first polymer and a second polymer in which a supramolecular interaction between the fullerene derivative and the second polymer is conjugated, .

In recent years, there have been many researches for the development and commercialization of various alternative energy sources such as solar, wind, marine, geothermal, and hydro power to reduce consumption of fossil fuels that cause environmental problems such as global warming and to prepare for depletion of fossil fuels Development is underway. In particular, solar power generation is considered to be one of the alternative energy sources closest to practical use.

Solar cells are used to produce electric power using solar light. The solar cell can be largely divided into a solar cell using crystalline silicon, a solar cell using amorphous silicon, and a solar cell using organic materials such as polymer. The most widely used solar cell is a crystalline silicon solar cell. However, since the crystalline silicon solar cell has a very high production cost, it is difficult to completely replace the conventional energy source because the power generation unit price rises . On the other hand, an organic solar cell using a polymer or the like has a merit that the production cost is very low, the flexibility is excellent due to the characteristics of the material, and various applications are possible. However, while the conversion efficiency (PCE) of other solar cells is improved to the level exceeding 20%, the light conversion efficiency of the organic solar cell is only about 5%, which can be improved There is a demand.

Polymer solar cells (PSC), which is a representative type of organic solar cells, have been studied to improve their properties. Among them, one of the most important achievements is penetration The interface of the large area donor D and the acceptor A is close to the region of exciton diffusion and dissociation while maintaining the percolating pathway. The bulk heterojunction (BHJ) structure can be formed. In the case of bulk heterojunction (BHJ) blends consisting of π-conjugated polymers and fullerene derivatives, which are currently attracting attention in the field of high-efficiency polymer solar cells (PSC), the power conversion efficiency (PCE) It is close to 10%.

Despite these advantages, the bulk heterojunction (BHJ) blends of polymers / fullerenes have severe geometrical instability due to the difficulty of intermixing the polymer and fullerene, Due to the sharp interface and low adhesion, a weak electron donor / electron donor junction structure is formed. In addition, a high efficiency bulk heterojunction (BHJ) shape is typically formed through a kinetic trapping process in the spinodal decomposition process between the two immiscible materials. As a result, it is exposed to heat as the polymer solar cell (PSC) or the like is driven, and proceeds to a macro-phase separation state at the interface of the bulk heterojunction (BHJ) The performance of the battery element is severely deteriorated. Furthermore, the active layer is susceptible to mechanical breakage due to a distinct bonding interface between the electron donor and the electron donor, low adhesion and ductility. For example, the bulk heterojunction (BHJ) blends of P3HT and PCBM have a much higher tensile modulus than pure polymers, which is related to the degree of cracking in the thin film have. For example, a 1: 1 mixture of P3HT and PCBM can easily break up to about 2% strain on a stretchable substrate. Such mechanical properties cause problems in that the mechanical durability and reliability of the polymer solar cell (PSC) is deteriorated in long-term use. Therefore, there is a need to improve the geometrical instability in the structure in order to solve the phase separation and mechanical problems in the electron donor-electron acceptor interface of bulk heterojunction (BHJ) blends.

Shape instability along the sharp interface as described above can be improved by adding a compatibilizer to appropriately accumulate the compatibilizer at the interface to reduce the interface tension and increase the adhesion force adhesion can be reduced to reduce inadequate interaction between the heterogeneous materials forming the interface. Thus, various commercial compatibilizers have been attempted, including heteroblock copolymers wherein a conjugated polymer of P3HT and fullerene is covalently bonded in a conjugated polymer / fullerene derivative bulk heterojunction (BHJ) structure.

However, most of the compatibilizers include covalently linked fullerene molecules capable of forming an appropriate enthalpic interaction with the acceptor phase, including the covalently bonded fullerenes It is a very difficult process to produce a compatibilizing agent. This is because, in general, the polymerization process is followed by a post polymerization step, in which the yield is lowered due to the low solubility of the fullerene. A more important problem is that when the covalent bond is added to the fullerene, the electrical characteristics of the electron acceptor such as energy level and electron mobility, which are crucial factors for the operation and efficiency of the polymer solar cell (PSC) . In particular, the development of suitable compatibilizers for bis-adduct fullerene bulk heterojunction (BHJ) systems has been considered as an alternative to significantly improve open circuit voltage (Voc) and light conversion efficiency (PCE) Addition of a covalent bond to a double adduct may seriously degrade the electron mobility and light conversion efficiency (PCE) while forming a tris-adduct, which is still a problem.

As a countermeasure against this problem, a method of using a noncovalent interaction has been considered. For example, electron rich polymers such as polyvinylpyridine are known to exhibit supramolecular interactions with electron-deficient fullerene molecules. In order to improve the thermal stability of the P3HT / PCBM shape, Sary et al. Have proposed P3HT (P3HT) to improve the thermal stability of the P3HT / PCBM shape in "A New Supramolecular Route for Using Rod-Coil Block Copolymers in Photovoltaic Applications" (Advanced Materials 22 (6), 763-768, 2010) A supramolecular route using a -b-poly (4-vinylpyridine) (P4VP) rod-coil block copolymer as a compatibilizer was proposed. However, when the block copolymer of P3HT and P4VP is used as a compatibilizer as described above, the thermal stability of the bulk heterojunction structure active layer can be improved by using the non-covalent supramolecular interaction, And the thermal stability is also required to be improved.

SUMMARY OF THE INVENTION The present invention has been made to overcome the problems of the prior art as described above, and it is an object of the present invention to improve the mechanical / thermal stability of a bulk heterojunction structure of an active layer by compensating for the shape instability of the bulk heterojunction structure. Further, It is an object of the present invention to provide a polymer solar cell capable of suppressing deterioration of solar cell characteristics such as efficiency.

According to an aspect of the present invention, there is provided a polymer solar cell including a bulk heterojunction structure of an electron acceptor region including an electron donor region including a polymer and an electron acceptor region including a fullerene derivative, Wherein the active layer comprises a first polymer obtained by polymerizing a conductive polymer having an alkyl group attached thereto; And a second polymer that is grafted to one or more monomers of the first polymer to form a copolymer, wherein the second polymer comprises the fullerene derivative and the supramolecule And is capable of forming supramolecular interaction.

At this time, part or all of the compatibilizer contained in the active layer may be distributed across the interface between the electron donor region and the electron acceptor region of the active layer.

Also, some or all of the first polymer portion of the compatibilizer may be located in the electron donor region, and some or all of the second polymer portion of the compatibilizer may be located in the electron acceptor region.

In addition, the number of carbon atoms contained in the alkyl group of the first polymer may be in the range of 4 to 12.

In addition, the conductive polymer may be thiophene.

Also, the conductive polymer may be P3HT (poly (3-hexylthiophene)).

Also, the second polymer may be one of polystyrene, poly (2-vinylryridine), P4VP, poly (methyl methacrylate), polyactide, polybutadiene, fullerene Or a mixture of two or more.

In addition, the polymer solar cell may have a reverse phase bulk heterojunction structure.

According to an embodiment of the present invention, there is provided a polymer solar cell including an active layer of a bulk heterojunction structure of a polymer and a fullerene derivative, wherein the conductive polymer having the alkyl group attached thereto is polymerized The thermal stability of the bulk heterojunction structure of the active layer can be improved by including the copolymer in which the second polymer capable of supramolecular interaction between the first polymer and the fullerene derivative is bonded as a compatibilizer, and further, even if the device is used for a long time, And has the effect of realizing a polymer solar cell capable of suppressing deterioration of solar cell characteristics such as efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
1 is a schematic view of a polymer solar cell including a rod-coil junction copolymer compatibilizer according to an embodiment of the present invention.
FIG. 2 is a flowchart of a method for producing a rod-and-coil conjugated copolymer compatibilizer according to an embodiment of the present invention.
FIG. 3 is an explanatory view of a synthesis process of a rod-and-coil conjugated copolymer according to an embodiment of the present invention.
4 is a graph of light conversion efficiency and current density of a P3HT / OXCBA polymer solar cell including a rod-and-coil junction copolymer compatibilizer according to an embodiment of the present invention.
5 is a graph of the light conversion efficiency of a solar cell at various bar-coil copolymer ratios according to an embodiment of the present invention.
FIG. 6 is a transmission electron microscope (TEM) image of a P3HT / OXCBA active layer film of a polymer solar cell comprising a heat-treated rod-and-coil junction copolymer compatibilizer according to an embodiment of the present invention after heat treatment.
FIG. 7 is a graph of light conversion efficiency of P3HT / PC ₆₁ BM and P3HT / PC ₇₁ BM polymer solar cells including a rod-and-coil junction copolymer compatibilizer according to an embodiment of the present invention.
8 is an optical microscope image of a P3HT / PC ₆₁ BM active layer film of a polymer solar cell including a rod-and-coil junction copolymer compatibilizer according to an embodiment of the present invention after heat treatment.
9 is a GI-WAXS image of a P3HT / PCBM active layer film of a polymer solar cell including a rod-and-coil junction copolymer compatibilizer according to an embodiment of the present invention before and after heat treatment.
10 is a graph showing a comparison of cracking energy of a P3HT / PC ₆₁ BM active layer film and a P3HT / OXCBA active layer film in a polymer solar cell including a rod-and-coil junction copolymer compatibilizer according to an embodiment of the present invention.
11 is a graph of the density simulation results for P3HT-g-P2VP and P3HT-b-P2VP in a D / A mixture at the lowest energy state according to an embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is capable of various modifications and various embodiments, and specific embodiments will be described in detail below with reference to the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

The terms first, second, etc. may be used to describe various components, but the components are not limited by the terms, and the terms are used only for the purpose of distinguishing one component from another Is used.

Hereinafter, exemplary embodiments of a polymer solar cell 100 including a rod-coil junction copolymer compatibilizer according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 illustrates a polymer solar cell 100 including a rod-coil junction copolymer compatibilizer according to an embodiment of the present invention. 1 (a), a polymer solar cell 100 including a rod-and-coil junction copolymer compatibilizer according to an embodiment of the present invention includes an electron donor 112 and an electron acceptor 114 The active layer 110 may include a polymer having a rod structure such as a P3HT 122 and a coil such as a P2VP 124. The active layer 110 may be formed of a material having a high dielectric constant, and a rod-coil junction copolymer 120 in which a polymer of a coil structure forms a junction structure.

More specifically, as can be seen in FIG. 1, a polymer solar cell 100 including a rod-and-coil junction copolymer compatibilizer according to an embodiment of the present invention includes an electron donor (Donor, And an active layer 110 including a bulk heterojunction structure of an area of an acceptor 114 that includes a dopant (D) 112 region and a fullerene derivative, And the active layer 110 may include a first polymer 122 polymerized with thiophene having an alkyl group attached thereto; And a second polymer (124) grafted to one or more monomers of the first polymer (122) to form a copolymer, wherein the second polymer (124) comprises a compatibilizer The polymer 124 is characterized in that it can form a supramolecular interaction with the fullerene derivative.

1 (b), the compatibilizer is distributed across the interface between the electron donor region and the electron acceptor region of the active layer 110, so that a clear difference between the P3HT-fullerene derivatives It is possible to effectively improve the thermal and shape instability due to the sharp interface, high interface tension, low adhesion, and the like. Further, part or all of the first polymer 122 portion of the compatibilizer is located in the region of the electron donor 112 of the active layer 110, and a part or all of the second polymer 124 portion of the compatibilizer And may be located in the region of the electron acceptor 114 of the active layer 110.

1 (c), a rod-coil block copolymer (P3HT-b-P2VP) distributed across the interface between the electron donor region and the electron acceptor region of the active layer 110 and a rod- (P3HT-g-P2VP) distribution simulation results. As shown in Fig. 1 (c), the distribution shapes of the rod-coil block copolymer (P3HT-b-P2VP) and the rod-coil junction copolymer (P3HT-g-P2VP) And it can be easily seen that the properties as a compatibilizer can be changed accordingly.

The active layer 110 may include an electron donor 112 including a polymer such as P3HT and an electron acceptor 114 including fullerene derivatives such as PC ₆₁ BM, PC ₇₁ BM, and OXCBA.

As the first polymer 122, a polymer of thiophene such as P3HT having an alkyl group attached thereto may be used. However, if it can be effectively embedded in the electron donor 112 made of P3HT or the like, Lt; / RTI > In forming the first polymer 122, various conductive polymers other than thiophene such as P3HT may be used. Thiophene may have the advantage of being able to produce a polymer with well-controlled molecular weight and dispersion by Grignard Metathesis (GRIM) polymerization method. However, the use of other conductive polymers improves the properties of polymer solar cells You may.

 In addition, the alkyl group can increase the solubility of the polythiophene to make a polymer solar cell (PSC) by a solution process or the like. The characteristics of the polymer solar cell may vary depending on the number of carbon atoms contained in the alkyl group (or the number of alkyl groups). In consideration of the shape and characteristics of the compatibilizer, Which is desirable.

The second polymer 124 may be at least one selected from the group consisting of polystyrene, poly (2-vinylryridine), P4VP, poly (methyl methacrylate), polyactide, polybutadiene Or a mixture of two or more of them may be used. Further, it is also possible to use fullerene as the second polymer 124 in consideration of the characteristics of the electron acceptor 114 including the fullerene derivative.

By including the rod-and-coil bonding copolymer 120 as a compatibilizing agent in the active layer 110 as described above, a clear interface between the electron donor 112 and the electron acceptor 124, a high interface tension, The thermal and shape instability due to adhesion and the like can be more effectively improved.

Further, the supramolecular interaction does not affect the electrical properties of the fullerene derivatives electron acceptor 114 and, therefore, even when a bis-adduct fullerene system is included, It is possible to improve the overall stability irrespective of the type of the electronic receiver 114. [ Furthermore, and more importantly, the bonding structure of the rod-coil junction copolymer 120 reduces energy penalties from the preferential location and stretches the copolymer chains, And even when compared with linear type rod-coil block copolymers having similar volume ratios and block lengths as seen in FIG. 1 (c), the compatibilizing efficiency can be further improved.

FIG. 2 shows a flowchart of a method for producing a rod-and-coil conjugated copolymer compatibilizing agent according to an embodiment of the present invention. One embodiment of the method for producing the rod-coil conjugated copolymer compatibilizing agent of the present invention includes a step (S210) of producing a P3HT-azide polymer by Grignard metathesis polymerization (GRIM), a RAFT polymerization (S230) of preparing a P3HT-P2VP conjugate (P3HT-g-P2VP) copolymer through a high-frequency-assisted click reaction .

Hereinafter, a method for producing a rod-and-coil joint copolymer compatibilizer according to the present invention will be described in detail with reference to FIGS. 2 and 3, for example, of a P3HT-P2VP (P3HT-g-P2VP) copolymer.

First, a P3HT-azide polymer is synthesized (S210) through Grignard metathesis polymerization (GRIM). At this time, it is preferable that the azide group has a low polydispersity index (PDI) value in consideration of effective synthesis of the P3HT-g-P2VP copolymer and formation of an aligned structure. In one embodiment of the present invention, a 3- (azidohexyl) thiophene monomer randomly distributed in a P3HT backbone was controlled in a proportion of 5 mol%. Further, the P3HT-azide polymer is not always required to be synthesized by Grignard Metathesis (GRIM) polymerization method, and can be applied without any particular limitations as long as it can appropriately synthesize a P3HT-azide polymer. Do.

A detailed description of a method for synthesizing P3HT-azide polymer using the Grignard metathesis (GRIM) polymerization method is as follows. In order to synthesize P3HT-azide polymer, 2,5-dibromo-3- (6-bromohexyl) thiophene) and 2,5- Starting from a mixture of dibromo-3-hexylthiophene. The mixture is mixed with isopropyl-magnesium chloride in the range of 0 to 20 degrees Celsius with tetrahydrofurane (THF) as a solvent in an inert gas atmosphere such as nitrogen, argon and the like.

Subsequently, a Ni (dppp) Cl2 suspension as a polymerization initiator is added to the mixture to initiate the polymerization reaction. An acid solution such as hydrochloric acid or nitric acid is added to the mixture to quench the polymerization reaction, neutralize the acidity of the solution with a basic solution such as ammonia, and then filter it.

The poly (3-hexylthiophene) polymer such as methanol, ethanol, and hexane does not dissolve and the impurities such as oligomers are dissolved. After removal of the impurities by Soxhlet extraction method and drying, P3HT- A P3HT-bromine polymer which is an intermediate of the zwitter polymer can be obtained.

The P3HT-Bromine polymer is then dissolved in a solvent that can be used for crystal induction in solution, such as Tetrahydrofurane (THF) or a solvent selected from chloroform, and nitrided to form an azide group In order to dissolve sodium (NaN ₃ ) and 18-crown-6 in a polar solvent such as alcohol and dihydro furane (DMF) uniformly, the azide ion can be transferred to the solvent selected in the polar solvent. (4, 7, 10, 13, 16-hexaoxacyclooctadecane), which is a phase transfer agent, maintained at 40 to 50 degrees Celsius and maintained in an inert gas atmosphere for about 8 hours, Bromine polymer solution. Thereafter, the mixed solution is filtered, and impurities including residual sodium nitrite (NaN ₃ ) are removed by the Soxhlet extraction method using alcohol such as methanol or ethanol as a solvent, and vacuum drying is performed to obtain P3HT-azide.

Also, the P2VP-alkyne polymer may be synthesized (S220) through a Reversible Addition-Fragmentation Transfer (RAFT) polymerization method. Synthesis of P2VP-alkyne polymer using the RAFT polymerization method is possible without any particular difficulty according to the prior art, so it is not discussed in detail here. An alkyne-terminated RAFT chain transfer agent can also be prepared according to the prior art.

Also, in this case as well, the P2VP-alkyne polymer is not necessarily synthesized by the Reversible Addition-Fragmentation Transfer (RAFT) polymerization method, and if the P2VP-alkyne polymer can be appropriately synthesized, It is possible.

The P2VP-alkene polymer is then coupled with the P3HT-azide polymer through a copper (I) -catalyzed click reaction as shown in Figure 3, A P3HT-g-P3VP copolymer having various P3HT volume fractions (f _P3HT ) can be synthesized (S230). Further, in proceeding the click reaction, it is preferable that the P3HT-azide polymer and the P2VP-alkyne polymer are dissolved in a solvent such as THF or chloroform.

At this time, the azide group is known to be a cross-linkable unit that is effectively crosslinked by light or heat, so that the click reaction between the P3HT-azide polymer and the P2VP-alkene polymer is completed Is very important. Thus, in order to suppress the possibility of self-cross-linking between P3HT-g-P2VP copolymers due to the presence of unreacted azides of the P3HT-g-P2VP copolymer, a high- microwave-assisted click reaction).

Examples: Synthesis of rod-coil junction copolymers and rod-coil block copolymers, fabrication and characterization of polymer solar cells using the same

The P3HT-P2VP (P3HT-g-P2VP) and P3HT-P2VP blocks (P3HT-b-P2VP) copolymers were prepared by azide-functionalized P3HT and Were synthesized using a microwave-assisted click reaction between alkyne-terminated P2VPs. Two types of azide-functionalized P3HT were prepared by Grignard Metathesis polymerization to form a junction or block structure, one of which was an azide at the end of the alkyl chain (P3HT-alkyl azide), while the azide group was attached to the end of the polymer chain (P3HT-end azide). The polymerization reaction conditions including reaction time and concentration, etc. is the amount of P3HT similar polymers have a molecular weight _{(M n (P3HT-alkyl azide} ) = 6.8kg / mol, M n (P3HT-end azide) = 6.4kg / mol) and narrow Was carefully adjusted to have a polydiversity index (PDI) of distribution. The composition of the 3- (azidohexyl) thiophene monomer was confirmed by 1 H-NMR, and its concentration was determined to be 5 (5) such that one P3HT-alkyl azide chain contained an average of two azide units. mol%. In order to better control the termination group functionalization of P3HT-end azide, the vinyl end capped P3HT was polymerized according to the prior art and then the vinyl groups were converted to hydroxyl and azide groups. The vinyl-terminated P3HT synthesized through the series of steps described above was confirmed to contain a very uniform bromine / vinyl terminated group by MADL-TOF analysis. The substitution reaction of the vinyl group was confirmed by 1 H-NMR And FT-IR. Finally, a well-defined mono-functionalized P3HT-end azide was obtained through a series of the above procedures. In addition, a series of P2VP-alkynes with various M _{n , P2VP} molecular weight values were polymerized using an alkyne-terminated Reversible Addition-Fragmentation Transfer (RAFT) chain transfer agent. The P2VP-alkyne polymer thus formed is then coupled to the P3HT-alkyl azide and the P3HT-end azide via a microwave-assisted click reaction, such that the volume ratios (f _P3HT ) of the _P3HT correspond respectively A series of P3HT-g-P2VP and P3HT-b-P2VP having two ranges (f _P3HT = 0.43 to 0.47 or 0.34 to 0.36) were formed. The molecular weight (M _n) and polydispersity index (PDI) of the P3HT was measured with the (calibrated) size exclusion chromatography (Size Exclusion Chromatography, SEC) calibrated with polystyrene (PS), a chemical for the copolymers of the four kinds of The structure and volume ratio were confirmed by < 1 > H-NMR. Table 1 below summarizes the properties of the series of P3HT-g-P2VP and P3HT-b-P2VP copolymers.

P3HT-P2VP
Copolymer type M _{n , P3HT}
[g / mol] P3HT
PDI M _{n , P2VP}
[g / mol] P2VP
PDI f _P3HT P3HT-g-P2VP
(0.43) join
(5 mol%) 6.8K 1.18 4.6K 1.13 0.43 P3HT-g-P2VP
(0.34) 7.1K 1.10 0.34 P3HT-b-P2VP
(0.47) block 6.0K 1.09 6.9K 1.10 0.47 P3HT-b-P2VP
(0.36) 11.7K 1.14 0.36

The structurally well-defined P3HT-g-P2VP and P3HT-b-P2VP rod-coil copolymers synthesized through the series of processes described above can be synthesized from P3HT and PC ₆₁ BM, PC ₇₁ BM, OXCBA, And applied to inverted type of BHJ PSC devices including fullerene derivatives. The structure of the reversed-phase polymer solar cell is used because the P2VP is preferentially coated on the oxide or charged surface during the spin coating process. Therefore, PEDOT: PSS (poly (3,4-ethylenedioxythiophene) (non-conductive P2VP layer) can be formed on top of the styrenesulfonate. In addition, a reversed-phase polymer solar cell can use a metal having a higher work function than a solar cell having a conventional structure, thereby improving the stability of the device, and it is possible to form an upper electrode using a non- And the manufacturing cost can be lowered.

A process for producing a polymer solar cell 100 including a rod-and-coil junction copolymer compatibilizer according to an embodiment of the present invention is as follows. First, ITO-coated glass substrates were ultrasonicated in a variety of solvent systems including acetone, 2% soap solution, deionized water and iso-propanol. ZnO was prepared by a sol-gel process using zinc acetate dihydra te (Zn (O ₂ CCH ₃ ) ₂ .H ₂ O) ₂ , 99.9%, 1 g) and ethanolamine (HOCH ₂ CH ₂ NH ₂ , 99.5%, and 0.28 g) were dissolved in anhydrous 2-methoxy ethanol (10 mL) for 24 hours or more with vigorous stirring to proceed a hydrolysis reaction. Then, a ZnO thin film having a thickness of about 40 nm was formed on the ITO substrate by spin-coating the sol-gel precursor solution at 4000 rpm. The film was heated in the atmosphere at 200? For 1 hour. After forming the ZnO layer, the subsequent processes were performed in a glove box in a nitrogen environment. P3HT / PCBM or PC ₇₁ BM (1: 0.67wt%) and P3HT / OXCBA (1: 0.6wt%) having a P3HT concentration of 60mg / ml were dissolved in ODCB and stirred at 90 ° C for more than 24 hours. The prepared solution was filtered with a 0.2 μm PTFE syringe filter. Mixed solution _{(P3HT / (PCBM, PC 71} BM or OXCBA) + P3HT-g-P2VP or + P3HT-b-P2VP) was made of P3HT concentration of 15mg / ml, the weight ratio of the polymer for the P3HT is from 0% to 15 %. &Lt; / RTI &gt; The active layer mixed solution was spin cast on ITO / ZnO substrate at 900 rpm for 40 seconds. Next, PEDOT: PSS (VAITRON AI 4083) was spin cast at 4000 rpm using X-triton 100 (1-1.5 wt%) as a process additive to form a soft layer about 40n thick on top of the above-described substrate , Followed by a heat treatment in a glove box at 120 ° C for 10 minutes. Finally, 100 nm as the top electrode was thermally evaporated in a high vacuum (<10 ^-6 Torr) environment to complete the device. The active layer area of the fabricated device was 0.09 cm &lt; ^{2 &} gt ;. The photovoltaic characteristics of the fabricated device were measured using a solar simulator (Peccell) equipped with an AM 1.5G filter. The intensity of the solar simulator was calibrated using an AIST-verified silicon photodiode. The current-voltage characteristics were measured using a Keithley 2400 SMU.

Then, as shown in FIG. 4, the performance of the series of P3HT / OXCBA bulk heterojunction devices including four kinds of copolymers of the same weight was measured while varying the heat treatment time at 150 ° C. The weight ratio of the rod-coil copolymer to P3HT was adjusted in the range of 0 to 15%, taking into account the weight of P3HT in the blends, where the initial light conversion efficiency (PCE) The maximum value of the weight ratio was about 5%. Optimized P3HT / OXCBA devices comprising 5% of the four rod-coil copolymers formed under the same conditions showed performance characteristics similar to those of the conventional device. Therefore, the compatibilizer according to one embodiment of the present invention is a polymer solar cell PSC) in the initial operation characteristic of the first embodiment. Further, the polymer solar cell 100 including the rod-and-coil junction copolymer compatibilizer according to an embodiment of the present invention can be manufactured at a temperature of 150 ° C as shown in Table 2 and FIG. 4 (a) And showed very improved thermal stability even after heat treatment.

Heat treatment time (hours) Open-circuit voltage (V) Short circuit current density (mA / cm ² ) Fill factor (FF) Light conversion efficiency (%) P3HT / OXCBA 0.5 0.87 9.30 0.61 4.94 72 0.49 7.48 0.44 1.61 P3HT-g-P2VP
(0.43) 0.5 0.89 9.28 0.63 5.21 72 0.84 9.20 0.60 4.65 P3HT-g-P2VP
(0.34) 0.5 0.88 9.19 0.64 5.12 72 0.81 8.93 0.60 4.37 P3HT-b-P2VP
(0.47) 0.5 0.89 9.30 0.61 5.11 72 0.76 7.64 0.58 3.36 P3HT-b-P2VP
(0.36) 0.5 0.89 8.50 0.63 4.82 72 0.77 7.17 0.52 2.88

 In particular, devices containing 5 wt% of P3HT-g-P2VP (0.43) exhibit superior thermal stability and show a light conversion efficiency (PCE) of greater than 4.6% even after 72 h of extended heat treatment at a temperature of 150 ° C , Which is the most stable thermal property among the bulk heterojunction devices based on P3HT reported so far.

In contrast, the light conversion efficiency (PCE) of a device containing a pure P3HT / OXCBA mixture fell to 1/3 of the initial light conversion efficiency (PCE) value after a long 72 hour heat treatment at a temperature of 150 ° C . This difference in thermal stability is due to the fact that the rod-and-coil copolymer distributes at the interface and effectively reduces the interfacial tension, and also the electron donor / electron acceptor (P3HT / OXCBA The phase separation between the first and second semiconductor layers is suppressed.

It can also be confirmed that the solar cell including the bonded copolymer has higher thermal stability than the case of using the block copolymer. For example, a solar cell containing 5 wt% of P3HT-b-P2VP (0.43) after heat treatment at a temperature of 150 ° C for 72 hours showed a significant reduction in light conversion efficiency (PCE) of 3.36% , And a 5 wt% P3HT-b-P2VP (0.36) showed a light conversion efficiency (PCE) value of 2.88% while a P3HT volume ratio (f _P3HT ) And P3HT-g-P2VP (0.34) having a P2VP block length similar to P3HT-g-P2VP (0.43) were found to be as high as 4.37% even after 72 hours long heat treatment at a temperature of 150 ° C It was confirmed that the light conversion efficiency (PCE) value can be maintained. These results indicate that the rod-coil compatibilizer having a junction structure is more effective in improving the sharp interface structure between the electron donor / electron donor (P3HT / OXCBA) and thus the bulk heterojunction polymer solar cell (PSC) It is possible to give higher thermal stability.

More direct evidence for the reduction of interfacial tension and inhibition of phase separation due to the rod-coil compatibilizer is obtained by studying the shape of the active layer using transmission electron microscopy (TEM) Can be. FIG. 6 shows a transmission electron microscope (TEM) image of a P3HT / OXCBA active layer film of a polymer solar cell including a heat-treated rod-and-coil junction copolymer compatibilizer according to an embodiment of the present invention after heat treatment.

First, a sample for transmission electron microscope (TEM) measurement was prepared for the above-mentioned experiment, and then P3HT / OXCBA was subjected to a heat treatment for 30 minutes, and then an elongated fibril-shaped P3HT Forming an interpenetrating network wherein the P3HT serves as a charge generating and efficient charge transfer path while providing a maximum interface area and thus a high polymer solar cell (PSC) efficiency . However, phase separation followed by gradual heat treatment was observed for a considerable time, and cluster formation of fullerene (20-50 nm) molecules was also observed (FIG. 6 (b)). Although the fullerene bis-adduct inhibits the fullerene nucleus from forming a contact close to a large cluster due to the various molecular structures of the regioisomer and the presence of the second substituent, the crystallinity ) Is relatively low, but if it is subjected to long-term heat treatment, large-scale phase separation and severe performance deterioration may result. On the other hand, in the bulk heterojunction (BHJ) film structure including 5 wt% of P3HT-g-P2VP and P3HT-b-P2VP, as shown in Figs. 6 (c) and 6 Even when subjected to a heat treatment for 24 hours, there was almost no change in shape. Considering the difference in shape, it can be seen that P3HT-g-P2VP and P3HT-b-P2VP can reduce interfacial tension and inhibit phase separation.

In order to verify the advantages of using a supramolecular interaction in the compatibilizing agent of a polymer solar cell (PSC), the rod-coil copolymer according to one embodiment of the present invention was used as another efficient solar cell, P3HT / PC ₆₁ BM and P3HT / PC ₇₁ BM (BHJ PSC). 7, P3HT / PC (1) containing 0% or 5% of P3HT-g-P2VP (0.43), P3HT-g-P2VP (0.34), P3HT- ₆₁ BM devices and P3HT / PC ₇₁ BM devices with thermal stability at 120 ° C. The P3HT / PC ₆₁ BM solar cell and the P3HT / PC ₇₁ BM solar cell prepared as a comparative sample show a light conversion efficiency (PCE) of 3.40% and 3.69%, respectively, Which is consistent with the characteristics of. The addition of the 5 wt% 4-bar-coil copolymer to each of the above solar cells did not affect the initial light conversion efficiency (PCE) value before the heat treatment, and showed almost similar efficiencies in all solar cells, . However, as a result of long-term heat treatment at 120 ° C, the comparative samples significantly degraded the photoconversion efficiency (PCE), while the P3HT-P2VP copolymer showed much better thermal stability. In particular, devices containing the P3HT-P2VP conjugated copolymer exhibited higher thermal stability for both the P3HT / PC ₆₁ BM device and the P3HT / PC ₇₁ BM device, as compared to the block copolymer. These results are consistent with those in the previously investigated P3HT / OXCBA system. The P3HT / PC ₆₁ BM solar cell containing 5 wt% of the covalent copolymer exhibited the most stable operating characteristics even when exposed to heat, showing a PCE characteristic of more than 3.0% even after heat treatment at 120 ° C for 72 hours, and P3HT- g-P2VP (0.34) showed the highest compatibilizing efficiency at P3HT / PC ₇₁ BM. The supramolecular interaction between the copolymer and the fullerene molecule is based on the unshared endothelial interaction between the electon rich nitrogen unit and the electron deficit fullerene moiety in P2VP, The universal compativilization of fullerene bulk heteropolymer solar cells (BHJ PSC) can be made effective regardless of the type of fullerene electron acceptor.

A more in-depth discussion of the differences in thermal stability can be made by observing the shape of the active layer using optical microscopy (OM) and Grazing Incidence x-ray scattering (GI-WAXS). 8 shows an optical microscope image of a P3HT / PC ₆₁ BM active layer film after heat treatment in a polymer solar cell 100 including a rod-and-coil junction copolymer compatibilizer according to an embodiment of the present invention.

Unlike the active layer containing P3HT / OXCBA, PCBM is known to form micro-sized clusters due to its strong crystallinity. Thus, using optical microscopy (OM) to observe clusters of micro size, quantitative data was obtained that can confirm the effect of compatibilizers in the form of P3HT / PC ₆₁ BM blends . In Figure 8 P3HT / PC ₆₁ BM comparative sample device and 5wt% of P3HT-g-P2VP (0.43) or in P3HT-b-P2VP (0.47) P3HT / PC 61 BM 120 ° C with respect to the device including, for 24 hours And shows an optical microscope (OM) image after heat treatment. As shown in FIG. 8 (a), the images show a dark area of a micrometer size due to the heat treatment, which seems to correspond to the case where the PCBM crystal grows to a length of 20 μm or more. On the other hand, FIGS. 8 (b) and 8 (c) show an optical microscope image of a device including P3HT-g-P2VP (0.43) and P3HT-b-P2VP (0.47) In the case of PCBM determination, the dark area is greatly reduced. These optical microscope (OM) images again show that the addition of a rod-coil copolymer compatibilizer with supramolecular interaction properties can effectively inhibit phase separation and further improve thermal stability in solar cell devices .

In addition, according to one embodiment of the present invention, not only the influence on the shape of the P3HT / PCBM mixture due to the addition of the rod-coil copolymer compatibilizer but also the thermal stability of the bulk heterojunction (BHJ) . FIG. 9 shows a two-dimensional GIWAXS image map of a P3HT / PCBM active layer film of a polymer solar cell including a rod-and-coil junction copolymer compatibilizer according to an embodiment of the present invention. As can be seen in Fig. 9, even when the rod-and-coil copolymer was added, no difference was observed in the arrangement structure of P3HT including domain spacing and stacking between adjacent P3HT chains (Fig. 9 (a )). However, after the heat treatment at 120 ° C for 24 hours, the crystallization peak of PC ₆₁ BM appears at 0.46 nm, as can be seen in FIG. 9 (b). According to one embodiment of the present invention, the device comprising the rod-coil copolymer compatibilizer shows that the PC ₆₁ BM crystallization peak exhibits a broad distribution centered at 0.45 nm intervals (Fig. 9 (c) P3HT-g-P2VP (Fig. 9 (d) P3HT-b-P2VP (0.47)), the peaks in the comparative sample films are very sharp and distinct, indicating the presence of PC ₆₁ BM crystals phase separated in bulk heterogeneous (BHJ) blends . These results again show that the solar cell characteristics such as thermal stability can be greatly improved due to the addition of the rod-coil copolymer compatibilizer according to one embodiment of the present invention.

FIG. 10 is a graph showing a comparison of cracking energy of P3HT / PC ₆₁ BM active layer film and P3HT / OXCBA active layer film in a polymer solar cell including a rod-and-coil junction copolymer compatibilizer according to an embodiment of the present invention.

The distinct and weak interface between the P3HT / fullerene derivatives in the bulk heterojunction (BHJ) layer results in the breakable mechanical properties of the active layer 110, which leads to mechanical integrity and &lt; RTI ID = 0.0 &gt; Which reduces reliability. In order to confirm the effect on the mechanical properties of the rod-coil copolymer compatibilizer according to the present invention in the bulk heterojunction (BHJ) active layer 110, the mechanical properties in the vertical and horizontal directions in the bulk heterojunction (BHJ) And the elastic modulus were measured. Accordingly, in order to investigate the mechanical properties of the P3HT / fullerene derivative bulk heteropolymer solar cell (BHJ PSC) according to an embodiment of the present invention, a double cantilever beam (DCB) The cohesive fracture energy of the included P3HT / PC ₆₁ BM and P3HT / OXCBA was measured (Fig. 10 (a)). The DBC sample was made of glass / P3HT (OXCBA or PCBM) / Pt / epoxy / glass structure. In addition, optimization conditions in a polymer solar cell (PSC) to prevent the diffusion of an epoxy resin to form the active layer 110 and the sputtered Pt layer were applied equally. Cohesive failure of the bulk heterojunction (BHJ) layer was observed in all samples. The critical cohesive fracture energy (Gc) value of the P3HT / PCBM bulk heterojunction (BHJ) film was measured to be 3.73 ± 0.18 Jm ^-2 , and these measurements indicate cracks in the P3HT / PCBM devices fabricated under similar conditions Lt; RTI ID = 0.0 &gt; energy. &Lt; / RTI &gt; It should be noted that the critical aggregation crack energy (Gc) values of P3HT / PCBM films containing 5% of P3HT-g-P2VP (0.43) and P3HT-b-P2VP (0.47) copolymers were 4.42 ± 0.75 and 4.32 ± And increased to 0.41 Jm ^-2 . A similar phenomenon was also observed on P3HT / OXCBA films. The critical aggregation crack energy (Gc) value of the P3HT / OXCBA film was 4.51 ± 0.11 Jm ^{- 2} , but the P3HT-g-P2VP (0.43) and P3HT-b-P2VP (0.47) The critical agglomeration crack energy (Gc) values were significantly improved to 5.46 ± 0.42 and 4.75 ± 0.20 Jm ^-2 , respectively. The preferential localization of the rod-coil copolymer compatibilizer at the electron donor / electron donor interface according to the present invention increases the entanglement density of the polymer chains across the interface, resulting in bulk heterojunction (BHJ) It is possible to increase the energy required to cause cohesive failure of the film. In addition, the covalent joint between the P3HT and P2VP blocks in the compatibilizer according to the present invention improves resistance properties to crack growth and debonding between the two phases.

Next, as an experimental example of the present invention, the tensile modulus in the bulk heterojunction (BHJ) active layer was measured, and it was confirmed that the tensile modulus of the stretchable polymer solar cell (PSC) It is closely related to implementation. In spite of this importance, the basic measurement of the tensile modulus in the polymer solar cell (PSC) active layer is hardly achieved. Recently, the elastic modulus of P3HT / PCBM BHJ thin films was measured using an underlying compliant substrate. However, in a high efficiency polymer solar cell (PSC), the thickness of the bulk heterojunction (BHJ) active layer is usually several hundreds of nanometers or less, and adhesion between the thin film and the lower substrate may also be exhibited. It is not easy to measure the mechanical properties of the substrate. Accordingly, in the present invention, a free-standing thin film is supported by using a water surface to support the tensile modulus accurately without damaging the sample or the lower substrate. A pseudo freestanding tensile test was performed. 10 (b) shows the elastic modulus of P3HT / OXCBA containing 0% and 5% of P3HT-g-P2VP (0.43) and P3HT-b-P2VP (0.47), respectively. In Fig. 10 (b), a photograph of a sample floating on the water surface is shown inserted. Made from linear stage in the attachment was achieved by the coated grip, a tensile test was 6 x 10 ^-5 / sec strain rate (strain rate) in a usual manner (stage) - fixed sample (grpping) is Polydimethylsiloxane (PDMS) lost. The Young's modulus of the P3HT / OXCBA film was measured to be 3.87 GPa while the tensile modulus of the P3HT-g-P2VP (0.43) and P3HT-b-P2VP (0.47) %, Respectively, which were significantly decreased to 3.03 and 2.79 GPa, respectively. In this measurement, the Young's modulus of the solar cell active layer was measured directly without the supporting substrate, and the accuracy was remarkably improved. More importantly, by adding a rod-coil copolymer compatibilizer, particularly a rod-coil copolymer compatibilizer having a conjugated structure, it is possible to provide a polymer solar cell (PSC) Energy can be improved, and tensile modulus can be reduced. The low modulus of the bulk heterojunction (BHJ) film allows cracking to be prevented against mechanical deformation such as warping or stretching of the polymer solar cell (PSC). Mechanical stability experiments also show that the rod-coil copolymer compatibilizer of the bond structure functions as a more efficient compatibilizer in polymer solar cells (PSC).

In order to investigate in detail the difference in the function and the nature of the interaction between P3HT-g-P2VP and P3HT-b-P2VP compatibilizer, in the present invention, a collection of the atoms has a smaller number of beads, Coarse-grained bead-spring molecular dynamics simulation was performed. Thus, a homogeneous homopolymer mixture of electron donor / electron donor (D / A) was prepared first, followed by energy minimization and simulated annealing to obtain the minimum energy structure . Next, the same number of simulated P3HT-graft-P2VP and P3HT-block-P2VP copolymers with the same molecular shape and length as P3HT-g-P2VP (0.43) and P3HT-b-P2VP . The same energy minimization and simulated annealing steps are then applied to the electron donor / electron acceptor (D / A) dual mixture + (P3HT-graft-P2VP or P3HT-block-P2VP) system Respectively. Accordingly, the density profile of the electron donor / electron donor (D / A) single polymer and copolymer is shown in FIG. As can be seen from Fig. 11, the P3HT-g-P2VP copolymer showed a higher spatial chain density near the interface between the electron donor (D) and the electron acceptor (A) phase, while the linear type P3HT- b-P2VP copolymer exhibited a wider density distribution area. From these results, it can be seen that the conjugated copolymer structure has the structural advantage of having a minimum energy state at the interface and a desirable separation state. Further, in order to more accurately compare the change in the interface width due to the addition of different kinds of copolymers, the interface width? Was calculated according to the conventional method. Thus, as can be seen in Table 3 below, the interface width? For the electron donor / electron acceptor (D / A) mixing system was calculated to be 1.033 ?, and the P3HT-b-P2VP and P3HT- , The interfacial width δ is widened to 1.194 σ and 1.272 σ, respectively.

The desired localization of the P3HT-g-P2VP copolymer at the interface widens the interface between the two components that are not mixed. The modified Irvine and Kirkwood equation is applied to the coarse-grained bead-spring molecular dynamics simulations to determine the efficiency of the copolymer's commercialization, The interface tension (γ _s ) of the system, which is directly related to the phase separation characteristics, can be calculated. The thus calculated interfacial tension (? _S ) values are shown in Table 3 below. The adhesive copolymers according to one embodiment of the present invention exhibited the lowest interfacial tension values in the immiscible blend system according to the present invention, Respectively. A wide interfacial width and a low interfacial tension depending on the preferable separation state of the bonded copolymer at the interface significantly improve the mechanical stability and the thermal stability in the insoluble heterogeneous mixture. Thus, the calculated simulation results clearly confirm once more that the conjugated copolymer structure is effective in improving the undesirable interfacial state between different insoluble mixtures.

Compatibilizers Interfacial width (δ) Interfacial tension (γ _s )  D / A blends 1.033σ 0.224σ ^-2 k _B T P3HT-b-P2VP 1.194σ 0.190σ ^-2 k _B T P3HT-g-P2VP 1.272σ 0.180σ ^-2 k _B T

The present invention discloses a polymer solar cell comprising a rod-coil junction copolymer compatibilizer. By adding the P3HT-g-P2VP compatibilizer to the bulk heterojunction polymer solar cell (BHJ PSC) as an embodiment of the present invention, it is possible to effectively improve the clear interface structure between the P3HT and the fullerene derivative, without deteriorating the electrical characteristics of the solar cell Thermal and mechanical stability can be remarkably improved. The P3HT-g-P2VP copolymer allows for improved overall thermal and mechanical stability of the bulk heterojunction polymer solar cell (BHJ PSC) regardless of the type of electron acceptor, including bis-adduct fullerenes . In addition, in the solar cell according to an embodiment of the present invention, the fracture energy was increased by more than 20% when compared with the conventional solar cell. Further, the structure of the copolymer of the copolymer was improved even when compared with the structure of the block copolymer Thermal stability, and mechanical stability. The effect of the conjugated copolymer structure could be confirmed by the results of coarse-grained molecular dynamics simulations.

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments described in the present invention are not intended to limit the technical spirit of the present invention but to illustrate the present invention. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents thereof should be construed as being included in the scope of the present invention.

100: Polymer solar cell comprising rod-coil junction copolymer compatibilizer
110: active layer
112:
114: Electronic receiver
120: rod-coil junction copolymer
122: first polymer
124: Second polymer

Claims (8)

And an active layer including a bulk heterojunction structure of an electron acceptor region including an electron donor region including a polymer and a fullerene derivative,
In the active layer,
A first polymer obtained by polymerizing a conductive polymer to which an alkyl group is attached; And
A second polymer that is grafted to one or more monomers of the first polymer to form a copolymer; and a polymer of the electron donor region and a fullerene derivative of the electron acceptor region, ),
Wherein the second polymer is capable of forming a supramolecular interaction with the fullerene derivative. The method according to claim 1,
Wherein part or all of the compatibilizer contained in the active layer is distributed across the interface between the electron donor region and the electron acceptor region of the active layer. 3. The method of claim 2,
Wherein some or all of the first polymer portion of the compatibilizer is located in the electron donor region,
Wherein part or all of the second polymer portion of the compatibilizer is located in the electron acceptor region. The method according to claim 1,
Wherein the number of carbon atoms contained in the alkyl group of the first polymer is in the range of 4 to 12. The method according to claim 1,
Wherein the conductive polymer is thiophene. The method according to claim 1,
Wherein the conductive polymer is P3HT (poly (3-hexylthiophene)). The method according to claim 1,
Wherein the second polymer is selected from the group consisting of polystyrene, poly (2-vinylryridine), P4VP, poly (methyl methacrylate), polyactide, polybutadiene, fullerene, By weight based on the total weight of the polymer solar cell. The method according to claim 1,
Wherein the polymer solar cell has a reversed phase bulk heterojunction structure.

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