KR20170140582A - Ethanol processible photovoltaic polymer and fullerene derivative, method for preparing the same, polymer solar cell comprising the polymer and fullerene derivative as active layer, and method for preparing the same - Google Patents

Abstract

The present invention relates to an ethanol-soluble photovoltaic polymer, and a preparation method thereof; and a polymer solar cell comprising the photovoltaic polymer as an active layer, and a preparation method thereof. More specifically, the present invention provides an electron donor compound represented by chemical formula 1, and an electron acceptor compound represented by chemical formula 2. In the chemical formula 1: Xs are each independently O, S, Se, or Te; Ys are each independently CN, Cl, F or H; m is an integer of 10-50; and n is an integer of 3-10. In the chemical formula 2, R is AA, and n is an integer of 3-10. Further, the present invention relates to a polymer solar cell which comprises the electron donor compound and the electron acceptor compound as active layers, and a preparation method thereof. According to the present invention, a polymer solar cell showing excellent power conversion efficiency can be provided through a process using ethanol, which is an environmentally-friendly solvent.

Description

TECHNICAL FIELD [0001] The present invention relates to an ethanol-soluble photovoltaic polymer and fullerene derivative, a method for preparing the same, a polymer solar cell including the photovoltaic polymer and a fullerene derivative as an active layer, cell comprising the polymer and fullerene derivative as active layer, and method for preparing same same}

The present invention relates to an ethanol-soluble photovoltaic polymer and a fullerene derivative, a process for producing the same, a polymer solar cell comprising the photoconductive polymer and a fullerene derivative as an active layer, and a process for producing the same.

Recently, a case has been reported in which a power conversion efficiency (PCE) of 10% or more is successfully achieved for a polymer solar cell (PSC) capable of solution processing, , Device structure and manufacturing conditions. Although significant progress has been made in the device efficiency and stability of PSCs over the past decade, there are still many challenges in realizing mass production of PSCs.

Most high performance PSCs are made using chlorine and / or aromatic solvents (such as chloroform (CF), chlorobenzene (CB), and 1,2-dichlorobenzene (DCB), etc.) as the processing medium. However, these chlorinated solvents are regarded as pollutants for drinking water because they exhibit various toxicological values and are very harmful to human health.

Recently, several meaningful studies have been attempted to develop alternative materials for halogenated solvents. For example, Hou et al. Used a nonhalogenated anisole solvent to make PSCs based on PBDTTT-S-TEG and PC ₇₁ BM-DEG, which is a mixture of dichlorobenzene (DCB), chlorobenzene (~ 4.5%) similar to processed solar cells (Non-Patent Document 1). Similarly, Jen and Li et al. Have found that a solvent mixture such as non-halogenated o -xylene, 1,2-dimethylnaphthalene (1,2-DMN), toluene and 1-methyl-2-pyrrolidone (NMP) (Non-Patent Documents 2 and 3).

Although non-halogenated solvents have been used successfully in PSC processing, these solvents are still toxic, very hazardous to industrial workers, and expensive to process waste solvents (Non-Patent Document 4). Therefore, there is a strong need for a green process with safety.

Conventionally, a manufacturing process of PSCs using water and alcohol as processing solvents has been proposed. Mwaura and colleagues have developed layer-by-layer film lamination technology from water soluble ionic bonding polymers (PPE-SO ₃ ^- , PPE-EDOT-SO ₃ ^- ) and water soluble ionic fullerene derivatives (C 60 -NH ₃ ⁺ , And a PCE of 0.01 to 0.04% was achieved through this (Non-Patent Document 5). Similar methods have also been attempted by researchers such as Qiao and TQ Nguyen et al. In which water soluble sodium poly [2- (3-thienyl) -ethoxy-4-butylsulfonate] (PTEBS: Na ⁺ Was used as an electron donor for bulk heterojunction and bilayer PSCs were used (non-patent documents 6 and 7). In addition, researchers at FC Krebs and colleagues found that poly [(4,4'-bis (2-ethylhexyl) dithieno [3,2-b: 2 ', 3' -d] silole) -2,6-diyl-alt- (2,1,3-benzothiadiazole) -4,7-diyl] and a dispersion of aqueous nanoparticles of PC ₆₀ BM in a roll- , And 0.55% PCE was achieved through this (non-patent document 8).

In addition, in the case of all bandgap polymers in which a hydrophilic nonionic amine group was introduced into the side chain, the photovoltaic characteristic of the solar cell was not exhibited regardless of the process conditions, And may form a complex with the fullerene center to disable hole transport in the active layer.

It is particularly noteworthy that the regulations on environmental protection and human health are strict in the world, especially in the European Union. The growing interest in environmental issues places emphasis on the importance of environmentally friendly solution processes for the production of PSCs, especially in the case of large-scale production of PSCs by roll-to-roll industrial printing technology. In addition, process stability and costs associated with waste treatment should also be considered seriously. Thus, the development of new photovoltaic materials that can be made with environmentally friendly solvents such as ethanol and water is a key issue in the field of organic photovoltaics.

On the other hand, there are several challenges to developing PSCs that are processed by environmentally friendly green solvents: (1) new photovoltaic structures that are soluble in green solvents should be redesigned, unlike processes that can be processed in conventional chlorinated organic solvents do. P- and N-type photoactive materials should have sufficient solubility (i.e., > 5 to 10 mg / mL) among environmentally friendly solvents. (2) Film formation and solid phase morphology should be adjusted to optimize charge separation, transport and extraction. Films prepared using hydrophilic ethanol or water are expected to have very different morphologies when compared to films made from chlorinated hydrophobic solvents (i.e., CF, CB, and DCB).

Although considerable efforts have been made to find alternative materials for halogenated and / or non-halogenated solvents, the successes so far are very rare.

Non-Patent Document 1: Yu Chen, Yong Cui, Shaoqing Zhang and Jianhui Hou; Polym. Chem., 2015, 6, 4089-4095. Non-Patent Document 2: Chu-Chen Chueh, Kai Yao, Hin-Lap Yip, Chih-Yu Chang, Yun-Xiang Xu, Keng-Shih Chen, Chang-Zhi Li, Peng Liu, Fei Huang, Yiwang Chen, Chen and Alex K.-Y. Jen, Energy Environ. Sci., 2013, 6, 3241-3248. Non-Patent Document 3: X. Guo, M.J. Zhang, C.H. Cui, J.H.Hou and Y.F. Li, ACS Appl. Mater. Interfaces, 2014, 6, 8190. Non-Patent Document 4:. "Material Safety Data Sheet MSDS". Section 11: Toxicological Information for the LD50 verification. Non-Patent Document 5: Jeremiah K. Mwaura, Mauricio R. Pinto, David Witker, Nisha Ananthakrishnan, Kirk S. Schanze, and John R. Reynolds, Langmuir 2005, 21, 10119-10126. Non-Patent Document 6: Q. Qiao and J. T. Mcleskey, Jr., Appl. Phys. Lett. 86, 153501 (2005). Non-Patent Document 7: J. H. Yang, A. Garcia and T. Q. Nguyen, Appl. Phys. Lett., 2007, 90, 103514. Non-Patent Document 8: Y. X. Nan, X. L. Hu, T. T. Larsen-Olsen, B. Andreasen, T. Tromholt, J. W. Andreasen, D. M. Tanenbaum, H. Z. Chen and F. C. Krebs, Nanotechnology, 2011, 22, 475301.

In order to solve the problems of the prior art, the present invention has been made to produce a polymer solar cell by an ethanol process which is an environmentally friendly solvent. For this purpose, an ethanol-soluble photopolymer and an ethanol- A compound, an electron acceptor compound and a process for producing the same. The present invention also provides a polymer solar cell including the photovoltaic polymer and the fullerene derivative as an active layer, and a method of manufacturing the same.

In order to solve the above problems,

There is provided an electron donor compound represented by the following formula (1): < EMI ID =

[Chemical Formula 1]

In this formula,

Each X is independently from each other O, S, Se or Te,

Each Y is independently of each other CN, Cl, F or H,

m is an integer of 10 to 50,

n is an integer from 3 to 10;

Further, in order to solve the above problems,

Claims 1. An electron acceptor compound represented by the following formula (2): < EMI ID =

(2)

,

, 또는

,

, or

Wherein R is

이고,

ego,

In the above formula, n is an integer of 3 to 10.

Furthermore, the present invention provides a polymer solar cell comprising a mixture of the electron donor compound represented by Formula 1 and the electron acceptor compound represented by Formula 2 as an active layer.

According to a preferred embodiment of the present invention, the mixing weight ratio of the electron donor compound to the active layer of the electron acceptor compound in the mixture may be 1: 1 to 1: 4.

Further, according to the present invention,

There is provided a process for preparing an electron donor compound represented by Chemical Formula 1, which comprises reacting a compound represented by Chemical Formula 3 and a compound represented by Chemical Formula 4 below:

(3)

Wherein R < ₁ > is

이고,

ego,

Wherein n is an integer from 3 to 10;

[Chemical Formula 4]

In this formula,

Each X is independently from each other O, S, Se or Te,

Each Y is independently of each other CN, Cl, F or H.

According to one preferred embodiment of the present invention, the compound represented by Formula 3 may be prepared by reacting a compound represented by Formula 5 and a compound represented by Formula 6:

[Chemical Formula 5]

[Chemical Formula 6]

In the above formula, n is an integer of 3 to 10.

Further, according to the present invention,

C60 fullerene with a compound represented by the following formula (7): < EMI ID =

(7)

In the above formula, n is an integer of 3 to 10.

According to another aspect of the present invention, there is provided a method for preparing a mixed solution comprising: preparing a mixed solution by dissolving the compound of Formula 1 and the compound of Formula 2 in an ethanol solvent; And forming an active layer by coating the mixed solution. The present invention also provides a method of manufacturing a polymer solar cell.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a polymer solar cell which exhibits excellent power conversion efficiency even in an ethanol process which is an environmentally friendly solvent.

1A is a diagram showing the formulas for photovoltaic polymer PPDT2FBT, an electron donor compound and an electron acceptor compound according to the present invention, which have been reported by the present inventors.
Figure IB is a graph showing TGA and DSC thermograms in solution and film of PPDT2FBT and the electron donor compound according to the present invention.
1C is a graph showing the UV / Vis absorption spectrum in a solution and a film of PPDT2FBT and an electron donor compound according to the present invention.
1D is a graph showing cyclic voltammograms (CV) for PPDT2FBT, an electron donor compound and an electron acceptor compound according to the present invention.
FIG. 2A is a graph showing a 2D-GIXS pattern for an electron donor compound according to the present invention, and FIG. 2B is a graph showing a line-cut pattern thereof.
3A and 3B are graphs showing the JV curve 3a and the EQE response curve 3b for the devices manufactured under the ethanol processing conditions at various D: A weight ratios.
4A and 4B are graphs showing the JV curve 4a and the EQE response curve 4b for the devices manufactured under bacchard processing conditions.
The Figures 5a to 5d are produced under optimized processing conditions of ethanol _{PPDT2FBT-A: Bis-C 60} -A AFM height image (5a), corresponds to the image (5b), TEM image (5c) and for mixing a thin film profile which is RSoXS Fig.
Figure 6 is purely PPDT2FBT-A polymers and PPDT2FBT-A: shows a light emission (photoluminescence) graph of the Bis-C ₆₀ -A mixture thin film.
7a and 7b are PPDT2FBT-A: a Bis-C ₆₀ -A mixture thin film 2D-GIXS pattern (7a) and a line-cut (7b) is a graph showing the pattern.
Figures 8a and 8b is a pure PPDT2FBT-A and Bis-C ₆₀ -A film (8a) and PPDT2FBT-A: the hole based on Bis-C ₆₀ -A mixture film-and E-is a graph illustrating the characteristics of the exclusive device graph JV .

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

In the present invention, an ethanol-soluble photopolymerizable polymer is prepared by reacting a poly [(2,5-bis (1,3-bis (2- (2- (2- methoxyethoxy) ethoxy) propan- Yl) benzo [c] [1,2,5] thiadiazole)] (PPDT2FBT-A) And a fullerene derivative (bis-fullerene-A) were synthesized (FIG. 1A). Successful PSCs were produced using ethanol, which showed ~ 0.75% PCE. All solution processes were performed in ambient air because the ethanol process provides operator-friendly conditions, which is also an advantage of the ethanol process.

Recently, the present inventors have found that poly ([2,5-bis (2-hexyldecyloxy) phenylene) -alt- (5,6-difluoro-4,7 (Thiophen-2-yl) benzo [c] [1,2,5] thiadiazole)] (PPDT2FBT) and has introduced a noncovalent Coulomb interaction in the polymer backbone, CB : A maximum PCE of ~9% was achieved using a mixture of diphenyl ether (DPE) (98: 2 vol%) as the processing solvent (Nguyen, TL; Choi, H .; Ko, SJ; Uddin, MA; Walker, B .; Yum, S .; Jeong, JE; Yun, MH; Shin, TJ; Hwang, S.; Kim, JY; Woo, HY Energy;

In the present invention, the same polymer backbone as the above-mentioned PPDT2FBT was used to produce an alcohol-soluble quasi-crystalline photoconductive polymer, but both of the electron donor (conjugated polymer) and the electron acceptor (fullerene derivative) And reproduced. Furthermore, the structure of the side chain was modified in order to control the solubility of the PPDT2FBT in the polar solvent, ethanol, because the new molecular structure-alcohol processing and the structure-property relationship of the solid phase morphology were required to be redefined. It was also possible to process the hexyldecyl substituents with ethanol, which is a green solvent, by substituting the oligoethyleneoxy group, 2- (2- (2-methoxyethoxy) ethoxy) ethoxy) propan-2-yloxy.

Accordingly, the present invention provides an electron donor compound represented by the following formula 1:

[Chemical Formula 1]

In this formula,

Each X is independently from each other O, S, Se or Te,

Each Y is independently of each other CN, Cl, F or H,

m is an integer of 10 to 50, preferably 15 to 20,

n is an integer from 3 to 10;

Claims 1. An electron acceptor compound represented by the following formula (2): < EMI ID =

(2)

,

, 또는

,

, or

Wherein R is

이고,

ego,

In the above formula, n is an integer of 3 to 10.

Furthermore, the present invention provides a polymer solar cell comprising a mixture of the electron donor compound represented by Formula 1 and the electron acceptor compound represented by Formula 2 as an active layer.

As can be seen from the data in the following examples, the mixing ratio by weight of the electron donor compound to the active layer of the electron acceptor compound in the mixture is preferably 1: 1 to 1: 4, And excellent power conversion efficiency is achieved.

The present invention also provides a process for preparing an electron donor compound represented by the above formula (1), wherein the compound of the formula (1) can be prepared by reacting a compound represented by the following formula (3) with a compound represented by the following formula , Preferably, the compound represented by Formula 3 may be prepared by reacting a compound represented by Formula 5 and a compound represented by Formula 6:

(3)

Wherein R < ₁ > is

이고,

ego,

Wherein n is an integer from 3 to 10;

[Chemical Formula 4]

In this formula,

Each X is independently from each other O, S, Se or Te,

Each Y is independently of each other CN, Cl, F or H.

[Chemical Formula 5]

[Chemical Formula 6]

In the above formula, n is an integer of 3 to 10.

The present invention also provides a method for preparing an electron acceptor compound represented by Formula 2, wherein the compound of Formula 2 is prepared by reacting C60 fullerene with a compound represented by Formula 7 below:

(7)

In the above formula, n is an integer of 3 to 10.

As described above, in the present invention, in order to provide a process for manufacturing an environmentally friendly solar cell, the above-mentioned ethanol-soluble photoconductive polymer is synthesized. By dissolving the compound of Formula 1 and the compound of Formula 2 in an ethanol solvent Preparing a mixed solution; And forming an active layer by coating the mixed solution. The present invention also provides a method of manufacturing a polymer solar cell.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the following examples are intended to assist the understanding of the present invention and should not be construed as limiting the scope of the present invention.

1. Molecular design, synthesis and characterization

Experimental details for the preparation of monomers and polymers have been described in detail in the following compound synthesis section.

Ethane) propan-2-yl-toluenesulfonate (Formula 6) was prepared according to the previously described process (Joke Vandenbergh, Jeroen Dergent, Bert Conings, TVV Gopala Krishna, Wouter Maes, Thomas J. Cleij, Laurence Lutsen, Jean Manca, Dirk JM Vanderzande, European Polymer Journal 47 (2011) 1827-1835). This was followed by coupling with 2,5-dibromohydroquinone using Williamson etherification to give 1,4-dibromo-2,5-bis (1,3-bis (2- (2- (2- Methoxyethoxy) ethoxy) ethoxy) propan-2-yloxy) benzene (Formula 3). The compound of the formula (1) is obtained by reacting the compound of the formula (3) with 4,7-bis (5-trimethylstannylthiophen-2-yl) -5,6-difluoro-2,1,3-benzothiadiazole ) Was reacted through a steel-coupling reaction. As a result, tris (dibenzylideneacetone) dipalladium (0) was used as a catalyst (yield, 90%) in toluene.

On the other hand, in the case of the compound of formula (2), it was prepared by reacting 3,4,5- [2- (2- (2-methoxyethoxy) ethoxy) ethoxy] benzaldehyde (formula 7) with fullerene C60 Followed by a Prato reaction in chlorobenzene with sarcosinic acid in 25% yield.

The compounds of formula (I) according to the present invention are useful not only in halogenated or aromatic solvents such as chloroform (CF), dichloromethane (DCM), CB, o- DCB and THF, but also in non-aqueous solvents such as DMF, DMSO, acetone, methanol, Halogenated or non-aromatic solvents. The number average molecular weight ( M _n ) of the compound of formula (1) was measured by gel permeation chromatography (GPC) using DCB as an eluent at 80 ° C and was found to be 16 kDa. According to thermogravimetric analysis (TGA) data, the polymer showed excellent thermal stability at a decomposition temperature ( T _d ) of ~ 380 ° C (5% weight loss) (see FIG. Also, from differential scanning calorimetry (DSC), endothermic and exothermic peaks were observed at 177 ° C and 162 ° C, indicating that crystalline melting ( T _m ) and recrystallization ( T _c ) (See FIG. 1B). The control material, PPDT2FBT, exhibited T _d , T _m and T _c values of 402, 317 and 308 ° C, respectively.

Figure 1c shows the UV-vis absorption spectrum of the compound of formula (1) in ethanol and also in film. The compound of Formula 1 has a molar extinction coefficient of 5.8 × 10 ⁴ M ^-1 cm ^-1 , which has a broad absorption spectrum in the 350-750 nm wavelength region, which is similar to that of PPCT2FBT, the reference material. The optical bandgap of the compound of formula (1) was measured to be 1.76 eV, which is the same as PPDT2FBT.

Substituting alkyl substituents with oligoethyleneoxy side chains in the conjugated backbone also has a significant effect in terms of electronic structure (i.e., frontier energy level). Figure 1 (d) shows cyclic voltammograms (CV) for the compounds of formulas (1) and (2). Referring to FIG. 1d, the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels are -4.95 eV and -3.19 eV. Further, in the case of the compound of formula 2, HOMO and LUMO levels were measured at -5.45 eV and -3.80 eV, respectively. These facts indicate that the oligomeric oxyoxy side chains have a strong influence on the electronic structures of the compounds, resulting in PPDT2FBT (HOMO: -5.45 eV, LUMO: -3.69 eV) and PC ₆₀ BM (HOMO: -5.9 eV, LUMO: , It can be seen that the HOMO and LUMO levels of the compounds of formulas (1) and (2) are increased.

Two dimensional grazing incidence X-ray scattering (2D-GIXS) was performed to evaluate the crystal packing and structural orientation of the compound thin film of Formula 1 under an ethanol process. Figures 2A and 2B show the 2D-GIXS pattern. 2A and 2B, the crystal characteristics of the compound thin film of Chemical Formula 1 show that up to the fourth order ((100), (200), (300) and (400) It can be seen that the bar and thin film have a very regular layer structure in the crystalline domain. From the primary (100) reflection peak, the interlaminar layer d spacing was found to be 22.85 Å, which is greater than the value of PPDT2FBT (20.7 Å), due to the longer oligoethylene oxy side chain. Furthermore, the (010) reflection peak corresponding to the pi-pi lamination was strong in the xy axis direction. These features imply that the polymer has a distinct edge-on packing structure in the film. The π-π lamination distance of the compound of formula (1) was measured to be 3.65 Å, which is a relatively smaller value than the low band gap polymer and its pendant PPDT2FBT (3.72 Å). This is due to the strong interaction between the compound backbones of formula (1) as well as the strong interaction between the oligoethylene oxy side chains through non-covalent hydrogen bonding interactions. Interestingly, the structural packing of the compound of formula (1) has been significantly changed from face-on to edge-on orientation by substituting alkyl substituents with oligoethyleneoxy side chains in the conjugated backbone. This significant change in structural packing can have a significant impact on the performance of the PSC device.

2. Insanity  Device fabrication and Photoelectricity  characteristic

In the present invention, a polymer solar cell was prepared using ethanol, which is an environmentally friendly processing solvent, as a solvent. For device fabrication, ITO / ZnO / PPDT2FBT-A : station having the structure of _{Bis-C 60 -A / MoO 3} / Ag - was used as a structure unit. The PPDT2FBT-A donor polymer and Bis-C to ₆₀ -A receptor, the mixed solution was dissolved in an ethanol solvent to form an active layer by spin coating onto the ZnO film. The solar cells processed from the resultant ethanol were tested and tested as a function of the weight composition of the PPDT2FBT-A donor (D) and the Bis-C ₆₀ -A receptor (A). Photovoltaic properties for the device and current density-voltage ( JV ) curves (100 mW / cm ² AM 1.5G solar irradiation) are shown in Table 1 and FIG.

D: A weight ratio V _OC
(V) J _SC
(mA / cm ² ) FF PCE (%) 1: 1 0.80 1.77 0.32 0.45 1: 1.5 0.81 2.36 0.39 0.75 1: 2 0.81 1.78 0.38 0.55 1: 1.5
(Bacardi) 0.80 1.07 0.38 0.33

Photovoltaic results show that the PPDT2FBT-A: Bis-C ₆₀ -A device exhibits optimized performance at a weight ratio of 1: 1.5 (D: A), and the average short-circuit current ( J _SC ) and 2.23 mA / cm ^2, is 0.79 V open circuit voltage _{(open-circuit voltage, V OC} ), as a 0.38 fill factor (fill factor, FF), exhibited a PCE of 0.67%. The highest efficiency of the device was 0.75% while the other D: A ratio devices showed 0.45% (1: 1) and 0.55% (1: 2) efficiencies. Above all, it is important to note that the present invention is the first report to report the meaningful photovoltaic properties of polymer solar cells fabricated in ethanol, an environmentally friendly solvent, using alcohol soluble photovoltaic materials. FIG. 3B is a graph showing external quantum efficiency (EQE), which also confirms the photovoltaic characteristics of the solar cell processed in the ethanol according to the present invention. 3, the optimum _{PPDT2FBT-A: Bis-C 60} -A apparatus generates a photoelectric current in a wide region of 400-700 nm, the maximum EQE value amounts to 18.31%. The photocurrents from the integration of the EQE reactions matched the J _SC values within the 2% error range. Furthermore, as an intuitive experiment that can show how environmentally friendly the ethanol processing according to the present invention is, a solar cell was manufactured using barcadi alcohol (ethanol content 75.5%), which is a usable solvent. Interestingly, the bacardly processed device also produced photovoltaic characteristics, with significant photovoltaic parameters: J _SC = 1.07 mA / cm ² , V _OC = 0.80 V, FF = 0.38, and PCE = 0.33%. The corresponding JV and EQE curves are shown in Figures 4a and 4b. These experiments demonstrate how environmental and human-friendly the process of the present invention is.

3. Morphology  And charge transport properties

PPDT2FBT-A: The surface morphology of the Bis-C ₆₀ -A film was analyzed using atomic force microscope (AFM) and transmission electron microscope (TEM). As shown in Figure 5a, ethanol processed _{PPDT2FBT-A: Bis-C 60} -A mixture film show a smooth surface morphology, the surface roughness was 0.81 nm. Referring to the corresponding image (Figure 5B), it can be seen that an interpenetrating network of ~ 10 nm in size is observed. More interestingly, referring to the TEM image in Figure 5c, complex highly interconnected fibrous structures of width ~ 10 nm are observed, which is in good agreement with the size observed from the AFM experiments. This interpenetrating fibrous morphology with a narrow fiber width is comparable to (~ 10 nm) the typical excitation diffusion length of the conjugated polymers and is therefore advantageous for better exciton diffusion / separation and is expected to improve charge transport through the fibers do. The cause of these fiber-nanostructures may be due to the strong? -Π interaction between the junction backbones of the PPDT2FBT-A polymer. Previously, it has been reported that a similar fibrous morphology is observed from PPDT2FBT: PC ₇₁ BM polymer solar cells (TL Nguyen, H. Choi, SJ Ko, MA Uddin, B. Walker, S. Yum, JE Jeong, MH Yun, TJ Shin, S. Hwang, JY Kim and HY Woo, Energy Environ. Sci . , 2014, 7 , 3040).

PPDT2FBT-A: Resonance soft X-ray scattering (RSoXS) technique was used to observe the mixed morphology of the Bis-C ₆₀ -A thin film in more detail. The photon energy at the carbon edge (284.4 eV) was employed to ensure tight contrast between the PPDT2FBT-A polymer and the Bis-C ₆₀ -A fullerene. Samples were prepared under the same conditions as in the preparation of the optimized device. Figure 5d PPDT2FBT-A as a function of the scattering vector q: is shown a _C-60 Bis -A scattering profile of the mixture. For these ethanol-processed mixed films, distinct reflections were observed at q = 0.0188 Å ^-1 , corresponding to an average domain spacing ( d- spacing) of 33.4 nm. Position of the reflection peak represents the main d -spacing between PPDT2FBT A polymer-donor or Bis-C ₆₀ fullerene -A receptor phases. Here, such d- spacings obtained from RSoXS were in good agreement with those calculated from TEM images. The center-to-center distance between the PPDT2FBT-A fibers was calculated as ~ 30 nm. This nanoscale-phase-separated morphology (~ 30 nm) of the ethanol-processed polymer solar cells is advantageous for causing efficient charge separation and transport through the enlarged donor / receptor interface region. Efficient exciton diffusion / separation of the mixed film can also be confirmed through photoluminescence (PL) quenching experiments (see FIG. 6). The pure PPDT2FBT-A and PPDT2FBT-A: Bis-fullerene-A mixed films were excited at 650 nm, corresponding to the main absorption of the polymer donor, and the mixed film exhibited a distinct PL extinction efficiency of 90.4%. These results PPDT2FBT-A: means that the C ₆₀ -A-Bis a transmission cross nano fiber morphology of the active layer leads to efficient exciton dissociation and charge transport to Bis-C ₆₀ -A-A from PPDT2FBT.

The packing structure of PPDT2FBT-A: Bis-C ₆₀ -A mixed film was also investigated by 2D-GIXS experiments under optimized conditions for the ethanol processed device. Highly reflective peaks from the PPDT2FBT-A polymer donor in the mixed film could be assigned (300) in the out-of-plane direction. However, it can be, seen that becomes when the polymer is mixed with the Bis-C ₆₀ -A receptor, a strong signal from the PPDT2FBT-A polymer about as shown in Figures 7a and 7b. This may be because the Bis-C ₆₀ -A receptors with bulky side chains interfere with the formation of the polymer packing structure in the mixed film. We believe that this is due to the low efficiency of the ethanol-processed devices. Further, it has been proposed that the face-on orientation can reduce the recombination of light excitons during charge separation (JR Tumbleston, BA Collins, L. Yang, AC Stuart, E. Gann, W. Ma, W. You and H. Ade, Nature Photon. , 2014, 8 , 385; BP Rand, D. Cheyns, K. Vasseur, NC Giebink, S. Mothy, Y. Yi, V. Coropceanu, D. Beljonne, J. Cornil, J .-L. Br? das and J. Genoe, Adv. Funct. Mater., is 2012, 22, 2987), also reported to alleviate the recombination of free carriers bar (S. Verlaak, D. Belionne, D. Cheyns, C. Rolin, M. Linares, F. Castet, J. Cornil and P. Heremans, Adv . Funct . Mater . 2009, 19 , 3809). Note the edge-on orientation of PPDT2FBT-A in the mixture as a key factor for lower PCE in PSC devices.

The hole (μ _h ) and electron (μ _e ) mobilities for pure polymers, fullerene receptors and their mixture films were evaluated using the space-charge limited current (SCLC) method. 8A and 8B, and also Table 2 below shows the measured hole (μ _h ) and electron (μ _e ) mobility values.

μ _h
(cm ² / V _s ) μ _e
(cm ² / V _s ) PPDT2FBT-A 3.53 x 10 ^-5 - Bis-C ₆₀ -A - 3.28 × 10 ^-7 PPDT2FBT-A: Bis-C ₆₀ -A 1.71 × 10 ^-6 4.02 x 10 < ^-8 >

First, the PPDT2FBT-A polymer was observed to have a high μ _h value of 3.53 × 10 ^-5 cm ² / Vs, similar to the values of low band gap polymers of various families. However, Bis-C ₆₀ -A was observed to have a much lower μ _e value of 3.28 × 10 ^-7 cm ² / Vs. This is due to the volume of the side chains displaced by fullerene. Thus, PPDT2FBT-A: Bis-C 60 -A mixture film as compared to the holes ^{(1.71 × 10 -6 cm 2 /} Vs) and e ^{(4.02 × 10 -8 cm 2 /} Vs) Mobility figures pure film in both 10 times lower than that of the control group. Significantly lower electron transport in mixed films results in poor μ _h / μ _e balance, which can lead to charge recombination and interfere with charge extraction. PPDT2FBT-A: This poor electron mobility of the Bis-C ₆₀ -A mixed film will be related to the low efficiency of the ethanol-processed device. Bulky side-chains for increasing solubility in Bis-C ₆₀ -A not only lower the charge transport capacity, but also affect the packing structure of the PPDT2FBT-A polymer, as evidenced by the GIXS experiments (Figs. 8a and 8b). Therefore, improving these properties will be the first task for further improving the photovoltaic performance of an ethanol-processed solar cell.

Experiment

1. Experimental General

A microwave reactor (BiotageInitiator (TM)) was used to synthesize the polymers. ^{The 1} H and ¹³ C NMR spectra were recorded on a Varian Mercury 300 MHz spectrometer. The number- and mass-average molecular weights of the polymers were measured on an Agilent GPC 1200 series for polystyrene standards at 80 ° C using o-dichlorobenzene as eluent as determined by gel-permeation chromatography (GPC). The cyclic voltammetric curves (CV) experiments were performed with a Versa STAT 3 analyzer. All CV measurements were performed in 0.1 M tetrabutylammonium-tetrafluoroborate (Bu ₄ NBF ₄ ) in acetonitrile, platinum electrode as a counter electrode, platinum electrode coated with a thin film polymer film as the working electrode, Ag / Ag (Scanning speed: 50 mV · s ^{- 1} ) using a ⁺ electrode as a reference electrode. Thermogravimetric analysis (2050 TGA V5.4A) and differential scanning calorimetry (DSC Q200 V24.4) were carried out under nitrogen (purity, 99.999%) at a heating and cooling rate of 10 ° C min ^-1 . The UV-vis absorption spectrum was measured using a UV-1800 spectrophotometer (Shimadzu Scientific Instruments). The PL spectra were measured using a Horiba Jobin Yvon NanoLog spectrophotometer at an excitation wavelength of 365 nm. The surface morphology of the ethanol-treated mixed film was measured by AFM (Veeco Dimension 3100 instrument) in tapping mode.

2. GIXS  And RSoXS  Measure

The GIXS experiments were performed at the Pohang Accelerator Laboratory, Beamline 3C (Korea). GIXS samples were prepared by spin-casting onto ZnO / Si substrates with optimized conditions for the ethanol-processed devices. An X-ray with a wavelength of 1.1179 Å was used. The incident angle (~ 0.12 °) was selected to irradiate the X-ray into the film. RSoXS measurements were performed with Advanced Light Source BL 11.0.1.2 (USA). PPDT2FBT-A: Bis-C ₆₀ -A film was prepared on PEDOT: PSS / ITO substrate under the same optimum layer conditions. The film was then floated in water and transferred to a 1.0 mm x 1.0 mm, 100 nm thick Si ₃ N ₄ film supported by a Si frame (Norcada Inc.) with a thickness of 5 mm x 5 mm and a thickness of 200 m.

3. Ethanol-processed Reverse structure Of PSCs  Fabrication and characterization

In order to evaluate the efficiency of the solar cell processed in ethanol, an inverted device with ITO / ZnO / active layer / MoO ₃ / Ag structure was prepared. The ITO-coated glass substrate was cleaned with various solvents, namely acetone, deionized water, and finally isopropyl alcohol. After the cleaning operation, the substrate was stored in an oven at 80 캜 for 20 minutes. The ITO substrate was plasma treated prior to spin-casting the ZnO layer. ZnO solution was prepared by dissolving zinc acetate dihydrate (Zn (O ₂ CCH ₃ ) ₂ (H ₂ O) ₂ , 99.9%, 1 g) and ethanolamine (HOCH ₂ CH ₂ NH ₂ , 99.5% -Methoxyethanol (CH ₃ OCH ₂ CH ₂ OH, > 99.8%, 10 mL) with vigorous stirring for over 24 hours to cause a hydrolysis reaction and proceed with aging. The ZnO solution was spin-coated on the ITO substrate at 4000 rpm to prepare a ZnO layer having a thickness of ~ 40 nm. The film was baked at 200 < 0 > C under ambient atmospheric conditions for 10 minutes. Next, the device was transferred to a N ₂ -filled glove box. The electron donor is PPDT2FBT-A were mixed in ethanol solvent processing and Bis-C ₆₀ -A electron acceptor. The concentration of the polymer donor (D) in the mixed solution was 5 mg · mL ^- 1: 1, and the mixing ratio of donor: acceptor (D: A) It gave to ^one. The mixed solution was stirred on a hot plate at 80 占 폚 for 1 hour before spin-casting onto the ITO / ZnO substrate. Spin-coating was performed at 1000 rpm for 40 s. The resulting thickness of the ethanol-treated mixture film was 50-60 nm. The device was baked in a vacuum chamber at 110 DEG C for 30 minutes to remove residual ethanol solvent in the active layer. Prior to evaporating approximately 10 nm of MoO ₃ and 120 nm of Ag, the substrate was placed in the evaporation chamber under high vacuum conditions (less than 10 ^-6 Torr) for at least 1 hour. The active area of the fabricated device was 0.09 cm ² , which was carefully measured with an optical microscope. The device's current density-voltage ( JV ) characteristics were measured with simulated AM 1.5G solar irradiation (100 mWcm ^-2 , Peccell: PEC-L01) under ambient atmospheric conditions. The solar simulator system satisfies Class AAB and ASTM standards. The intensity of the solar simulator was calibrated carefully using a standard silicon reference cell with a KG-5 visible color filter. J- V characteristics were collected using a Keithley 2400 SMU. EQE results were obtained using a spectral measurement system (K3100 IQX, McScience Inc.). The system uses an optical chopper (MC 2000 Thorlabs) in monochromatic light from a 300 W xenon arc lamp filtered by Mono chromate (Newport) and in ambient atmospheric conditions. EQE data were obtained under dark conditions. Theoretical J _SC values were obtained by integrating the EQE values with the AM 1.5G solar spectrum, which were within 2% error range of the measured J _SC .

Synthesis of donor and acceptor materials

Compounds of formula 1 and formula 2 were synthesized according to scheme 1 and scheme 2:

[Reaction Scheme 1]

[Reaction Scheme 2]

(Reagents and reaction conditions: a) sodium tert-butoxide, ethanol, reflux, 48 h; b) Pd ₂ (dba) ₃ , tris (o-tolyl) phosphine, toluene and DMF; c) sarcosonic acid, chlorobenzene, N ₂ , reflux)

Additional compounds:

Fullerene (C60) and 1,4-dibromo-2,5-dihydroxybenzene (Formula 5) were purchased from Solamer and Sigma-Aldrich respectively and used without further purification. Propane-2-yl-toluenesulfonate (Formula 4), 3,4,5- [2- (2-methoxyethoxy) ethoxy) - (2-methoxyethoxy) ethoxy) ethoxy] benzaldehyde 7 was prepared according to Joke Vandenbergh, Jeroen Dergent, Bert Conings, TVV Gopala Krishna, Wouter Maes, Thomas J. Cleij, Laurence Lutsen, Jean Manca, Dirk J.M. Vanderzande; European Polymer Journal 47 (2011) 1827-1835 and YongshuXie, MisahoAkada, Jonathan P. Hill, Qingmin Ji, Richard Charvet and Katsuhiko Ariga; Chem. Commun., 2011, 47, 2285-2287.

Ethoxy) propane-2-yloxy) benzene (represented by the formula (I) 3) Synthesis of

1,4-Dibromo-2,5-dihydroxybenzene (Formula 5) (1.0 g, 3.8 mmol) was dissolved in ethanol (20 mL). Sodium tert -butoxide (0.77 g, 7.9 mmol) was then added. The mixture was stirred at room temperature under an atmosphere of N ₂ for 1 hour. Thereafter, the compound of formula 6 (4.2 g, 7.9 mmol) was added dropwise. The reaction mixture was stirred at reflux temperature for 48 hours. After partial evaporation of the solvent, H ₂ O was added and the mixture was extracted with dichloromethane (CH ₂ Cl ₂ ). The organic extract was washed with 10% sodium hydroxide (NaOH) solution, dried over anhydrous magnesium sulfate (MgSO _4), then evaporated the solvent to give the crude product. After column chromatography (SiO _2, eluent ethyl acetate / methanol 95/5), the compound (0.7g, 60%) of formula (3) colorless oil form.

^{1 H NMR (400 MHz, CDCl} 3): δ = 7.30 (2H, s), 4.33 (2H, m), 3.69 (8H, m), 3.56 (30H, m), 3.48 (8H, m) 3.30 (12H , s); ¹³ C NMR (100 MHz, CDCl ₃ ): 150.4, 121.8, 112.5, 80.6, 71.7, 70.5, 70.4, 70.3, 58.9.

Synthesis of Compound (1)

(300 mg, 0.30 mmol), Formula 4 (199.5 mg, 0.30 mmol), tris (dibenzylideneacetone) dipalladium (0) (4 mol%), tri o -tolyl) phosphine (8 mol%) and 2 mL of toluene were added. The reaction mixture was heated in a microwave reactor at 80 캜 (10 min), 100 캜 (10 min) and 140 캜 (40 min). The polymer was end-capped (0.05 g, 0.14 mmol) by the addition of 2-tributylstannylthiophene (0.05 g, 0.14 mmol) and the mixture was further reacted at 140 ° C for 20 minutes. The solution was allowed to cool and 2-bromothiophene (0.09 g, 0.53 mmol) was added via syringe. The reaction solution was further heated at 140 占 폚 for 20 minutes. After the reaction was completed, the resulting polymer was precipitated in hexane and further purified by Soxhlet extraction method using hexane and chloroform. The polymer of formula (1) extracted in chloroform was precipitated in hexane, filtered and dried under vacuum.

Yield: 85%. Number average molecular weight (Mn) = 16 kDa, polydispersity index (PDI) = 2.2. ^{1 H NMR (400 MHz, CDCl} 3): δ (ppm) (8H, m), 3.80 (2H, br), 7.80 (2H, br) .

Synthesis of Compound of Formula 2

Chlorobenzene (30 mL), fullerene _{(C 60) (500 mg,} 0.7mmol), formula 7 (822 mg, 1.4mmol), and Sar-conic acid (187 mg, 2.1mmol) in the mixture was refluxed for 4 hours under N _2. After evaporation of the solvent, column chromatography purification on a silica gel column was performed on the residue. A small amount of unmodified C60 was produced by elution with CH ₂ Cl ₂ . Fractions containing the compound of formula (2) were obtained using the CH ₂ CH ₂ / MeOH (95/5) eluant (340 mg, 25%).

In summary, a novel quasi-crystalline alternating polymer (PPDT2FBT-A) and a fullerene derivative (Bis-C ₆₀ -A) which can be processed into a non-toxic and environmentally friendly ethanol solvent were prepared. The present invention proposes a simple and useful method for preparing an ethanol-soluble substance by substituting an alkyl group with an oligoethyleneoxy group. According to the present invention, the influence of the side chain changes on the optical properties of the polymer was negligible, but the electrochemical and thermal properties and especially the crystalline orientations changed significantly. It was also the first time that PSCs with PCE values of the order of 0.75% could be produced by inverted structures by ethanol processing. Although PCE levels are still low, there is much room to improve PCE by clearly understanding morphology, structural orientation, exciton generation and decomposition, etc., for the compounds according to the present invention. As a result of analyzing the performance of the device according to the present invention, ethanol-soluble materials and ethanol solvent are considered to be excellent alternatives for roll-to-roll printing of high performance solar cells.

Claims (8)

An electron donor compound represented by the following Formula 1:
[Chemical Formula 1]

In this formula,
Each X is independently from each other O, S, Se or Te,
Each Y is independently of each other CN, Cl, F or H,
m is an integer of 10 to 50,
n is an integer from 3 to 10; An electron acceptor compound represented by Formula 2:
(2)

,

, or

Wherein R is

ego,
In the above formula, n is an integer of 3 to 10. A polymer solar cell comprising a mixture of an electron donor compound according to claim 1 and an electron acceptor compound according to claim 2 as an active layer. The method of claim 3,
Wherein a mixing weight ratio of the electron donor compound to the active layer of the electron acceptor compound in the mixture is 1: 1 to 1: 4. A process for preparing an electron donor compound according to claim 1, comprising the step of reacting a compound represented by the following formula (3) and a compound represented by the following formula (4)
(3)

Wherein R < ₁ >

ego,
Wherein n is an integer from 3 to 10;
[Chemical Formula 4]

In this formula,
Each X is independently from each other O, S, Se or Te,
Each Y is independently of each other CN, Cl, F or H. 6. The method of claim 5,
Wherein the compound represented by Formula 3 is prepared by reacting a compound represented by Formula 5 and a compound represented by Formula 6:
[Chemical Formula 5]

[Chemical Formula 6]

In the above formula, n is an integer of 3 to 10. A method for producing an electron acceptor compound according to claim 2, comprising the step of reacting C60 fullerene with a compound represented by the following formula (7)
(7)

In the above formula, n is an integer of 3 to 10. Preparing a mixed solution by dissolving an electron donor compound according to claim 1 and an electron acceptor compound according to claim 2 in an ethanol solvent; And forming an active layer by coating the mixed solution.

Images