WO2024080719A1 - Zinc oxide nanoparticle thin film with improved mechanical flexibility - Google Patents

Abstract

The present application provides a zinc oxide nanoparticle thin film with improved mechanical flexibility.

Description

Zinc oxide nanoparticle thin film with improved mechanical flexibility

This application relates to a zinc oxide nanoparticle thin film with improved mechanical flexibility.

The ability to fabricate thin film devices on a variety of flexible substrates using solution-based manufacturing processes has sparked interest in flexible electronics. Integrating multilayer electronic thin films on plastic substrates enables the development of lightweight, inexpensive, and flexible optoelectronic devices such as organic light-emitting diodes (OLEDs), photovoltaic devices (OPVs), and photodetectors (OPDs). there is. Each component must be composed of an electronic material that is electrically conductive and robust under various mechanical stresses to develop efficient and mechanically robust optoelectronic devices. Metallic and semiconducting polymers are excellent candidates for flexible electrodes and photoactive materials. However, device performance may be reduced due to poor electrical contact with metal electrodes and poor stability in ambient air. Developing high-performance polymer-based electronic devices requires an interfacial layer that is electrically conductive and stable in air.

Metal oxide nanoparticles (MONPs) such as zinc oxide (ZnO) and nickel oxide have been intensively studied as interfacial layer materials for polymer-based optoelectronic devices. This is because metal oxide nanoparticles can easily form an electrically conductive thin film through a simple solution process without a high-temperature heat treatment process due to their high crystallinity. This low-temperature process is advantageous for integration into the underlying polymer semiconductor thin film, which may deteriorate at high temperatures. Additionally, metal oxide nanoparticle thin films exhibit high charge carrier mobility and wide bandgap that enable effective charge transport and high transmittance, respectively, resulting in high performance of organic optoelectronic devices such as OPV and OPD. The metal oxide nanoparticle thin film acts as an encapsulation layer on the polymer-based photoactive layer, improving the air stability of OPV and OPD. However, metal oxide nanoparticles are brittle due to weak interactions between nanoparticles, so despite the advantages described above, they have rarely been used in flexible optoelectronic devices.

Due to high electron mobility (> 0.002 cm ² /Vs), wide band gap (> 3.3 eV), and small diameter (< 100 nm), ZnO nanoparticles (ZnO NPs) serve as an electron transport layer in organic optoelectronic devices. It is one of the most studied materials as ETL). These properties have led to high-performance and air-stable OPVs and OPDs, but have rarely been used in flexible electronic devices. Fan researchers reported improved flexibility of ZnO-NP:polystyrene composite thin films (P. Fan, D. Zhang, Y. Wu, J. Yu, T.P. Russell, “Polymer-modified ZnO nanoparticles as electron transport layer for polymer-based solar cells" Adv. Funct. Mater. 30 (2020), 2002932), the use of electrically insulating polymers may reduce the electrical properties of ZnO-NP-based ETL and result in phase separation. Additionally, the solubility of polystyrene in common organic solvents such as o-xylene hinders the application of alcohol-based ZnO-NP solutions. Therefore, the optimal additive for mechanically flexible ZnO-NP thin films has 1) small size (to avoid phase separation), 2) π-conjugated backbone (for better charge transport), and 3) high solubility in polar solvents. (for better miscibility in ZnO-NP alcohol solution).

The present application seeks to provide a zinc oxide nanoparticle thin film with improved mechanical flexibility.

However, the problem to be solved by the present application is not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the description below.

The first aspect of the present application is a dendrimer comprising a compound represented by the following Chemical Formula I, an oligomer represented by the following Chemical Formula II, or a compound represented by the following Chemical Formula I at the terminal; and zinc oxide nanoparticles:

[Formula Ⅰ]

;

[Formula Ⅱ]

;

In Formula I and Formula II,

R ¹ is hydrogen or -OR ^a -R ^b ,

R ^a is a C _1-10 alkylene group,

R ^b is an ammonium halide salt, and the ammonium salt is an ammonium salt (-NH ₃ ⁺ ), a C _1-20 primary alkylamine, a secondary alkylamine, or a tertiary alkylamine containing at least one nitrogen, C _3-10 It is an ammonium salt of a heterocycloalkyl group, or a C _3-10 heteroaryl group, and in the ammonium halide salt, the halide ion is F ^- , Cl ^- , Br ^- , or I ^- ,

However, except for the case where R ¹ is all hydrogen,

R ² is

,

,

,

,

, or

ego,

m is 0 or 1, n is an integer from 1 to 10,

The dashed line is the connection part.

The second aspect of the present application provides a flexible electronic device comprising the flexible film according to the first aspect as a charge transfer layer.

The flexible membrane according to embodiments of the present application includes a multicharged conjugated electrolyte (MCCE) and zinc oxide nanoparticles, and zinc oxide is formed due to strong ionic interaction between the multicharged conjugated electrolyte and the zinc oxide nanoparticles. Nanoparticles can form aggregates, which has the characteristic of improving the mechanical flexibility of the membrane.

The flexible film according to embodiments of the present application does not contain an electrically insulating polymer such as polystyrene, but rather contains a polyion conjugated electrolyte that does not affect the electrical properties of the thin film, and can be used as a charge transfer layer in a flexible electronic device. It has the characteristic of not deteriorating the electrical characteristics of the device.

The flexible membrane according to the embodiments of the present application has the characteristic that cracks do not occur even when tensile bending is repeated several times at a bending radius (r) of about 1.5 mm in a thickness range of about 500 nm or less due to improved flexibility. The flexible membrane according to the embodiments of the present application has the characteristic of not cracking even when tensile bending is repeated several or hundreds of times with a bending radius (r) of about 2.5 mm in a thickness range of about 100 nm or less due to improved flexibility. there is. The flexible membrane according to the embodiments of the present application does not crack even when tensile bending is repeated about 300 times or about 250 times with a bending radius (r) of about 2.5 mm in a thickness range of about 100 nm or less due to improved flexibility. There is a characteristic.

The flexible electronic device according to the embodiments of the present application includes the flexible membrane of the present application as a charge transfer layer, so that the original electrical properties are maintained even after tensile bending is repeated several or hundreds of times with a bending radius (r) of about 2.5 mm. There is.

The flexible film according to the embodiments of the present application has the feature of being able to be manufactured through a simple solution process that does not deteriorate the electrical properties of the electronic device.

Figure 1 shows the synthesis route of diphenylfluorene pyridinium bromide (PFPBr) in an example of the present application.

Figures 2 and 3 show ¹ H and ¹³ C NMR spectra of Compound 2, according to an example of the present application.

Figures 4 and 5 show ¹ H and ¹³ C NMR spectra of compound 3, according to an example of the present application.

Figures 6 and 7 show ¹ H and ¹³ C NMR spectra of PFPBr in an example of the present application.

Figure 8 is a schematic diagram of zinc oxide nanoparticles (ZnO nanoparticles; ZnO-NP) and the chemical structures of KBr and PFPBr (a), and various amounts of KBr and PFPBr for ZnO-NPs, according to an example of the present application. Dynamic light scattering (DLS) analysis results and corresponding solution images for solutions containing ZnO-NP, ZnO-NP:KBr, and ZnO-NP:PFPBr (numbers in parentheses indicate the molar concentration of Br ^- (i.e., [ Br ^- ]) is shown.) (b) is shown.

Figure 9 is a photograph of PFPBr solutions of various concentrations dissolved in 2-methoxyethanol, according to an example of the present application.

Figure 10 shows Br 3d core-level XPS spectra of ZnO-NP, ZnO-NP:KBr and ZnO-NP:PFPBr thin films containing various amounts of KBr and PFPBr (numbers in parentheses are (a) Schematic showing the composition of ZnO-NP:KBr and ZnO-NP:PFPBr complexes at various molar concentrations of KBr and PFPBr (representing the molar concentration of Br ^- ) and the composition of free Br as a function of the molar concentration of KBr and PFPBr. Area of the Zn-Br subpeak relative to the peak area (A _Zn-Br /A _freeBr ) (b), and ZnO-NP:PFPBr with Zn ²⁺ -Br ^- -N ⁺ ionic bond at the ZnO-NP/PFPBr interface. A schematic diagram of the complex (c) is shown.

Figure 11 shows ZnO-NP (a), ZnO-NP:KBr ([Br ^- ] = 1.6 μM) (b), and ZnO-NP:PFPBr ([Br ^- ] = 1.6, in an example of the present application) μM) This is an optical microscope image of the thick film in (c) after bending five times at a bending radius (r) = 1.5 mm (scale bar: 20 μm, arrow indicates the bending direction).

Figure 12 shows ZnO-NP (a, d, g), ZnO-NP:KBr ([Br ^- ] = 1.6 μM) (b, e, h), and ZnO-NP: After five bendings at r = 1.5 mm of the thick film of PFPBr ([Br ⁻ ] = 1.6 μM) (c, f, i) Scanning electron microscope ⁽ SEM) images of ZnO-NP, ZnO-NP:KBr ^, and ^ZnO -NP: Schematic diagram (j) showing different surface morphologies of PFPBr thick films is shown.

Figure 13 shows ZnO-NP (a, d), ZnO-NP: KBr ([Br ^- ] = 1.6 μM) (b, e), and ZnO-NP: PFPBr ([Br ^- ] = 1.6 μM) Atomic force microscopy (AFM) image of the thick film in (c, f) after five bendings at r = 1.5 mm (scale bar: 2 μm (top), 0.5 μm (bottom) ).

Figure 14 shows, in an example of the present application, ZnO-NP (a, d, g), ZnO-NP:KBr ([Br ^- ] = 4.0 μM) (b, e, h), and ZnO-NP: SEM images of a thin film of PFPBr ([Br ^- ] = 4.0 μM) (c, f, i) after (a to f) and before (g to i) bending at r = 1.5 mm (where: Images were obtained at different magnifications (3Х10 ⁴ , 1Х10 ⁵ , and 2Х10 ⁵ , respectively), the inset images show the corresponding schematics of spin-cast ZnO-NP, ZnO-NP:KBr and ZnO-NP:PFPBr thin films, where Gray circles represent ZnO-NPs).

Figure 15 is a device structure (a) and an energy level diagram (b) of a flexible organic photodetector (OPD), according to an embodiment of the present application; Photograph of flexible OPD without tensile stress (left) and flexible OPD tensile stressing to r = 2.5 mm (right) (scale bar: 1 cm) (c); Responsivity of flexible OPDs fabricated using ZnO-NP, ZnO-NP:KBr ([Br ^- ] = 0.6 μM), and ZnO-NP:PFPBr ([Br ^- ] = 0.6 μM) thin films using ETL/HBL. ; R) (d) and detectability (D ^* ) (e) (before (left) and after (right) 250 repeated tensile bending at r = 2.5 mm); Front optical microscopy images of flexible OPDs fabricated by ETL/HBL of ZnO-NP, ZnO-NP:KBr and ZnO-NP:PFPBr after 250 bendings at r = 2.5 mm (arrows indicate tensile bending direction, scale bar: 100 μm) (f); and a schematic view (left: side view, right: top view) of flexible OPD containing ZnO-NP and ZnO-NP:KBr ETL/HBL after tensile bending (g).

Figure 16 shows the external quantum efficiency (EQE) measurement results of flexible OPD manufactured using ZnO-NP, ZnO-NP:KBr, and ZnO-NP:PFPBr thin films as ETL/HBL in an example of the present application, (a) before 250 bends at r = 2.5 nm; and (b) shows the measurement results (red arrows indicate reduced parameters due to device failure after repeated bending).

Hereinafter, with reference to the attached drawings, implementation examples and embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. However, the present application may be implemented in various different forms and is not limited to the implementation examples and examples described herein. In order to clearly explain the present invention in the drawings, parts unrelated to the description are omitted, and similar parts are given similar reference numerals throughout the specification.

Throughout this specification, when a part is said to be “connected” to another part, this includes not only the case where it is “directly connected,” but also the case where it is “electrically connected” with another element in between. do.

Throughout this specification, when a member is said to be located “on” another member, this includes not only the case where the member is in contact with the other member, but also the case where another member exists between the two members.

Throughout the specification of the present application, when a part “includes” a certain element, this means that it may further include other elements rather than excluding other elements, unless specifically stated to the contrary.

As used herein, the terms “about,” “substantially,” and the like are used to mean at or close to a numerical value when manufacturing and material tolerances inherent in the stated meaning are presented, and to aid understanding of the present application. It is used to prevent unscrupulous infringers from unfairly exploiting disclosures that contain precise or absolute figures.

The terms “step of” or “step of” as used throughout the specification herein do not mean “step for.”

Throughout this specification, the term "combination(s) thereof" included in the Markushi format expression means a mixture or combination of one or more selected from the group consisting of the components described in the Markushi format expression, It means containing one or more selected from the group consisting of the above components.

Throughout this specification, description of “A and/or B” means “A or B, or A and B.”

Throughout this specification, the term “alkyl” or “alkyl group” refers to a linear or branched alkyl group having 1 to 12 carbon atoms, 1 to 10 carbon atoms, 1 to 8 carbon atoms, or 1 to 5 carbon atoms. and all possible isomers thereof. For example, the alkyl or alkyl group includes methyl group (Me), ethyl group (Et), n-propyl group ( ⁿ Pr), iso-propyl group ( ⁱ Pr), n-butyl group ( ⁿ Bu), and iso-butyl group. ( ⁱ Bu), tert-butyl group (tert-Bu, ^t Bu), sec-butyl group (sec-Bu, ^sec Bu), n-pentyl group ( ⁿ Pe), iso-pentyl group ( ^iso Pe), sec -Pentyl group ( ^sec Pe), tert-pentyl group ( ^t Pe), neo-pentyl group ( ^neo Pe), 3-pentyl group, n-hexyl group, iso-hexyl group, heptyl group, 4,4-dimethylphene Examples include, but are not limited to, tyl group, octyl group, 2,2,4-trimethylpentyl group, nonyl group, decyl group, undecyl group, dodecyl group, and isomers thereof.

Hereinafter, embodiments of the present application have been described in detail, but the present application may not be limited thereto.

The first aspect of the present application is a dendrimer comprising a compound represented by the following Chemical Formula I, an oligomer represented by the following Chemical Formula II, or a compound represented by the following Chemical Formula I at the terminal; and zinc oxide nanoparticles:

[Formula Ⅰ]

;

[Formula Ⅱ]

;

In Formula I and Formula II,

R ¹ is hydrogen or -OR ^a -R ^b ,

R ^a is a C _1-10 alkylene group,

R ^b is an ammonium halide salt, and the ammonium salt is an ammonium salt (-NH ₃ ⁺ ), a C _1-20 primary alkylamine, a secondary alkylamine, or a tertiary alkylamine containing at least one nitrogen, C _3-10 It is an ammonium salt of a heterocycloalkyl group, or a C _3-10 heteroaryl group, and in the ammonium halide salt, the halide ion is F ^- , Cl ^- , Br ^- , or I ^- ,

However, except for the case where R ¹ is all hydrogen,

R ² is

,

,

,

,

, or

ego,

m is 0 or 1, n is an integer from 1 to 10,

The dashed line is the connection part.

In one embodiment of the present application, the ammonium salt of R ^b is ammonium salt (-NH ₃ ⁺ ), trimethylammonium salt, triethylammonium salt, tripropylammonium salt, Methylammonium salt, ethyl ammonium salt, propyl ammonium salt, dimethyl ammonium salt, ethyl methyl ammonium salt, methyl propy ammonium salt, diethy ammonium salt, ethyl propy ammonium salt, dipropylammonium salt, ethyl dimethyl ammonium salt, dimethyl propy ammonium salt, diethyl methyl ammonium salt, ethyl methyl propy ammonium salt, Select from methyldipropylammonium salt, diethylpropylammonium salt, ethyldipropylammonium salt, pyridinium salt, aziridinium salt, azetidinium salt, pyrrolidinium salt, piperidinium salt, azepanium salt, azocenium salt, and imidazolium salt. It may include one or more, but may not be limited thereto. Here, the halide ion of the ammonium halide salt may be a fluoride ion, a chloride ion, a bromide ion, or an iodide ion.

In one embodiment of the present application, R ¹ is

It may be, but may not be limited to this.

In one embodiment of the present application, the compound represented by Formula I may be diphenylfluorene pyridinium bromide (PFPBr) represented by the following Formula 1, but may not be limited thereto:

[Formula 1]

.

In one embodiment of the present application, the oligomer represented by Formula II may be represented by the following Formula 2, but may not be limited thereto:

[Formula 2]

;

In Formula 2,

R ² is

,

,

,

,

, or

ego,

m is 0 or 1, n is an integer from 1 to 10,

The dashed line is the connection part.

In one embodiment of the present application, a compound represented by Formula I; An oligomer represented by the above formula (II); And the dendrimer containing the compound represented by Formula I at the terminal may be a multicharged conjugated electrolyte (MCCE) containing multiple ionic functional groups at the terminal. The flexible membrane of the present application includes the zinc oxide nanoparticles and the polyion conjugated electrolyte, and strong ionic interaction (multivalent interaction) between the multiple ionic functional groups of the polyion conjugate electrolyte and the zinc oxide nanoparticles. Due to this, zinc oxide nanoparticles can form aggregates, which has the characteristic of improving the mechanical flexibility of the membrane. Therefore, the multiple ionic functional groups included in the basic structure of Chemical Formula I are the main structure that can derive the effects of the present invention, and the basic skeleton is a single compound, which is used not only for the polyion conjugate electrolyte represented by Chemical Formula I, but also for this The oligomer represented by Formula II with an expanded structure, and the dendrimer containing multiple structures of Formula I at the terminal, can have the same, similar, or improved level of effect as the polyion conjugate electrolyte represented by Formula I. It can be expected that there will be.

In one embodiment of the present application, a compound represented by Formula I; An oligomer represented by the above formula (II); And in the dendrimer containing the compound represented by Formula I at the terminal, the multiple ionic functional groups may refer to R ^b .

Typically, a dendrimer refers to a polymer material or macromolecule in which a branch-like unit structure repeatedly extends from the center, and consists of a central core, an interior branching unit, and an exterior surface functional group. It is composed of functional groups). In one embodiment of the present application, the dendrimer may be used without particular limitation as long as it is a polymer of a typical dendrimer structure that can bind a compound containing multiple ionic functional groups as external surface functional groups.

In one embodiment of the present application, the dendrimer may be a dendrimer of polyethyleneimine (PEI), polypropyleneimine (PPI), or polyamidoamine (PAMAM), but may not be limited thereto. In one embodiment of the present application, the dendrimer may be a 1st to 5th generation dendrimer, but may not be limited thereto. In one embodiment of the present application, the dendrimer may further include a linker compound that assists in the connection between the internal branch unit and the external surface functional group, and the type of the linker compound may vary depending on the type of the dendrimer. there is.

In one embodiment of the present application, the dendrimer of polyethyleneimine may be, as a non-limiting example, a dendrimer of 1st to 3rd generation polyethyleneimine represented by the following structure, but may not be limited thereto:

,

, and

.

In one embodiment of the present application, ● in the dendrimer structure of polyethyleneimine may mean an external surface functional group, and when the external surface functional group is diphenylfluorene pyridinium bromide (PFPBr) represented by Formula 1 above. , the dendrimer skeleton may be bonded to the 2nd carbon of the fluorene group as shown in the structure below, and may further include a linker compound such as an amine:

.

In one embodiment of the present application, the halide ion (X ^- ) of R ^b (i.e., the halide ion of the polyion conjugate electrolyte) and Zn ²⁺ of the zinc oxide nanoparticles coordinate to form the zinc oxide nanoparticles. It may be agglomerating.

In one embodiment of the present application, the process of agglomerating the zinc oxide nanoparticles will be described in more detail: When the polyion conjugated electrolyte and the zinc oxide nanoparticles are mixed in a solvent, the halogenated ions of the polyion conjugated electrolyte ( ^{( ​ ​ ​ ​} Agglomerated halide chelated zinc oxide nanoparticles can be produced. Thereafter, the flexible membrane of the present application can be obtained by manufacturing a solution containing the polyion conjugated electrolyte and the zinc oxide nanoparticles into a membrane through a solution process.

In one embodiment of the present application, the solvent may be an alcohol solution of methanol, ethanol, propanol, 2-methoxyethanol, or isopropyl alcohol, but may not be limited thereto.

In one embodiment of the present application, the solution process may be a solution process commonly used to manufacture films of electronic devices, and non-limiting examples include spin casting, spray, or inkjet ( It may be an inkjet method, but may not be limited thereto.

In one embodiment of the present application, the diameter of the zinc oxide nanoparticles may be from about 1 nm to about 100 nm, but may not be limited thereto.

In one embodiment of the present application, the thickness of the flexible membrane may be about 1 nm to about 1 μm, but may not be limited thereto. In one embodiment of the present application, the thickness of the flexible film can be appropriately adjusted depending on the characteristics of the flexible electronic device to which it is applied. In one embodiment of the present application, the thickness of the flexible film for application to a flexible electronic device may preferably be from about 10 nm to about 100 nm, and more preferably from about 40 nm to about 80 nm.

In one embodiment of the present application, the flexible membrane may not crack even if it is bent about 300 times or more or about 250 times or more at a bending radius of about 2.5 mm in a thickness range of about 100 nm or less.

In one embodiment of the present application, the flexible membrane does not contain an electrically insulating polymer such as polystyrene, but contains a single molecule polyion conjugated electrolyte that does not affect the electrical properties of the thin film, and is a flexible electronic device. It has the characteristic of not deteriorating the electrical characteristics of the device when used as a charge transfer layer.

A second aspect of the present application provides a flexible electronic device comprising the flexible film according to the first aspect as a charge transfer layer.

Detailed description of parts overlapping with the first aspect of the present application has been omitted, but the content described in the first aspect of the present application can be applied equally even if the description is omitted in the second aspect of the present application.

In one embodiment of the present application, the flexible electronic device may include one or more selected from flexible organic light-emitting diodes, flexible solar cells, flexible optical sensors, perovskite light-emitting diodes, flexible transistors, and flexible chemical sensors. However, it may not be limited thereto.

In one embodiment of the present application, the flexible electronic device includes the flexible membrane of the present application as a charge transfer layer, so that the original electrical properties are maintained even after tensile bending is repeated several or hundreds of times with a bending radius (r) of about 2.5 mm. You can.

Hereinafter, the present application will be described in more detail using examples. However, the following examples are merely illustrative to aid understanding of the present application, and the content of the present application is not limited to the following examples.

[Example]

1. Synthesis and characterization of PFPBr

ingredient

All chemicals used in the synthesis were reagent grade and used without further purification. Pyridine was purchased from Sigma Aldrich and Junsei Chemical Company, respectively. 1,6-dibromohexane was purchased from Tokyo Chemical Industry Company. Mercaptopropionic acid and acetonitrile were purchased from Alfa Aesar. Pyridine was pyrogallol, and N,N-dimethylformamide, potassium carbonate, and sulfuric acid were purchased from Daejeong. Silica gel (Merck, 230 mesh to 400 mesh) was used for chromatographic purification of all intermediates and target molecules. All other chemicals and solvents were purchased from Sigma Aldrich, Fisher Scientific, or Acros Chemical Company.

Synthesis and characterization

Figure 1 shows the synthetic route of PFPBr. Pyrocatechol appended-fluorene (compound 2 in FIG. 1) is described in reference BH Lee, IH Jung, HY Woo, HK Shim, G. Kim, and K. Lee, “Multi-Charged Conjugated Polyelectrolytes as a Versatile Work Function Modifier for Organic Electronic Devices", Adv. Funct. Mater. 24 (2014), 1100-1108. It was prepared in 88% yield from commercially available 9-fluorenone. Precursor compound 3 was synthesized according to standard methods using 1,6-dibromohexane. Afterwards, pyridine was easily coupled to compound 3 to produce PFPBr in 76% yield. PFPBr is characterized as an alkylated spiro-type diphenylfluorene with six water-soluble pyridinium groups. The structure of PFPBr was characterized by ¹ H-NMR), ¹³ C-NMR, electrospray ionization mass spectrometry (ESI-MS), and component analysis. Details of synthesis and characterization are as follows.

Synthesis of 9,9-Bis(3,4,5-trihydroxyphenyl)fluorene (Compound 2)

Sulfuric acid (0.018 mL) was added slowly to a mixture of 9-fluorenone (3.0 g, 16.6 mmol), pyrocatechol (9.2 g, 73.0 mmol) and 3-mercaptopropionic acid (0.13 mL) at room temperature. The reaction mixture was stirred vigorously at 60° C. under argon gas for 3 hours. After the reaction mixture was cooled to room temperature, the resulting mixture was quenched by adding toluene. A pink precipitate was obtained through vacuum filtration and washed with 150 mL of warm water. After drying, a light yellow solid was obtained.

Yield: 88%; ¹ H NMR (400 MHz, methanol-d ₄ ): δ 7.74 (d, 2H), 7.41 (d, 2H), 7.31 (t, 2H), 7.23 (t, 2H), 6.23 (s, 4H); ¹³ C NMR (100 MHz, methanol-d ₄ ): 153.62, 146.46, 141.50, 138.53, 132.87, 128.42, 128.29, 127.62, 120.93, 120.78, 108.99, 65.96 (Figures 2 and 3 ).

9,9-Bis(3,4,5-tris(6-bromohexyloxy)phenyl)fluorine (9,9-Bis(3,4,5-tris(6-bromohexyloxy)phenyl)fluorine) (compound 3) Synthesis of

To a solution of compound 2 (2.0 g, 4.83 mmol) in acetonitrile (100 mL) was added anhydrous K ₂ CO ₃ (4.4 g, 31.9 mmol). After stirring for 5 minutes, 1,6-dibromohexane (7.8 g, 31.9 mmol) was added dropwise to the solution. The resulting mixture was stirred vigorously at 80° C. for 24 hours under argon gas. After the reaction mixture was cooled to room temperature, the solvent was removed in vacuo. The reaction mixture was extracted with dichloromethane (150 mL). The organic layer was separated, washed with water (50 mL), dried over anhydrous MgSO ₄ , and the solvent was evaporated to obtain a yellow solid. The pure product was separated through silica gel column chromatography using ethyl acetate:hexane (1/10, v/v) as eluent.

Yield: 15%; ¹ H NMR (400 MHz, CDCl ₃ ): δ 7.76 (d, 2H), 7.41 (d, 2H), 7.38 (t, 2H), 7.30 (d, 2H), 6.34 (s, 4H), 3.89 (t , 4H), 3.74 (t, 8H), 3.41 (t, 12H), 1.85 (m, 12H), 1.69 (m, 12H), 1.45 (m, 24H); ¹³ C NMR (100 MHz, CDCl ₃ ): 152.53, 151.19, 141.03, 140.23, 137.11, 127.67, 126.25, 120.39, 107.60, 73.18, 68.90, 65.72, 34.14, 34. 00, 33.87, 33.02, 32.87, 32.71, 30.32, 29.90 , 29.86, 29.33, 28.26, 28.19, 28.09, 27.50, 25.52, 25.46, 25.39, 22.90 (Figures 4 and 5).

Synthesis of PFPBr

Pyridine (3.1 g, 3.9 mmol) was added to a solution of compound 3 (4.6 g, 3.3 mmol) in acetonitrile (30 mL). The resulting mixture was stirred vigorously at 80° C. for 24 hours under argon gas. After the reaction mixture was cooled to room temperature, the solvent was removed in vacuo. The reaction mixture was extracted with dichloromethane (150 mL). The organic layer was separated, washed with water (100 mL), dried over anhydrous MgSO ₄ , and the solvent was evaporated in vacuum. The crude product was purified via column chromatography (silica gel, ethyl acetate/hexane (1/3, v/v)) to give a white solid.

Yield: 95%; ¹ H NMR (400 MHz, ethanol-d ₆ ): δ 9.22 (t, 12H), 8.63 (t, 3H), 8.58 (t, 3H), 8.14 (m, 12H), 7.84 (d, 2H), 7.45 (d, 2H), 7.38 (d, 2H), 7.31 (t, 2H), 6.38 (s, 4H), 4.76 (m, 12H), 3.87 (t, 4H), 3.74 (t, 8H), 2.04 ( m, 12H), 1.68 (m, 12H), 1.44 (m, 24H); ¹³ C NMR (100 MHz, Ethanol-d ₆ ): 153.38, 152.19, 151.93, 146.73, 146.63, 145.99, 142.33, 141.11, 129.46, 129.40, 128.74, 128.62, 126.9 7, 121.27, 108.16, 79.49, 73.95, 69.47, 66.65 , 62.68, 62.61, 57.52, 57.38, 57.17, 56.96, 56.74, 56.53, 32.43, 30.71, 29.88, 26.68, 26.59, 26.56, 26.41, 17.95, 17.76, 1 7.58, 17.39, 17.20, 17.01, 16.82 (Figures 6 and 7) .

2. Preparation and characterization of zinc oxide nanoparticles and membranes containing them

2-1. Materials and Methods

ingredient

Zinc oxide nanoparticles (ZnO-NPs) (2.5 wt% in isopropyl alcohol) with an average particle size of 10 nm to 15 nm were purchased from Sigma Aldrich. The electron donor poly[(2,6-(4,8-bis(5-(2-ethylhexyl-3-fluoro)thiophen-2-yl)-benzo[1,2-b:4 ,5-b']dithiophene))-alt-(5,5-(1',3'-di-2-thienyl-5',7'-bis(2-ethylhexyl)benzo[1', 2'-c:4', 5'-c']dithiophene-4,8-dione)](poly[(2,6-(4,8-bis(5-(2-ethylhexyl-3-fluoro) thiophen-2-yl)-benzo[1,2-b:4,5-b']dithiophene))-alt-(5,5-(1',3'-di-2-thienyl-5',7 '-bis(2-ethylhexyl)benzo[1',2'-c:4',5'-c']dithiophene-4,8-dione)] and 2,2' as an acceptor. -[[12,13-bis(2-ethylhexyl)-12,13-dihydro-3,9-diundecylbisthieno[2",3":4',5']thieno[2' ,3':4,5]pyrrolo[3,2-e:2',3'-g][2,1,3] benzothiadiazole-2,10-diyl]bis[methylidine (5, 6-difluoro-3-oxo-1H-indene-2,1(3H)-diylidene)]]bis[propandinitrile] (2,2'-[[12,13-Bis(2-ethylhexyl) )-12,13-dihydro-3,9-diundecylbisthieno[2",3":4',5']thieno[2',3':4,5]pyrrolo[3,2-e:2',3 '-g][2,1,3]benzothiadiazole-2,10-diyl]bis[methylidyne(5,6-difluoro-3-oxo-1H-indene-2,1(3H)-diylidene)]]bis[ propanedinitrile]; Y6) was purchased from Brilliant Matters. ,7-(9,9-dioctylfluorene)] (poly [(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7- (9,9-dioctylfluorene)]; PFN) was purchased from 1-Material. PEDOT:PSS aqueous solution (both AI 4083 and PH 1000 grades) was purchased from Heraeus and used as is. All solvents and potassium bromide (KBr) used in the examples of the present invention were purchased from Sigma Aldrich. Transparent polyimide film (100 μm thick) used as a flexible OPD substrate was purchased from Mitsubishi Gas Chemical.

Dynamic light scattering (DLS)

The size distribution of ZnO-NP, ZnO-NP:KBr, and ZnO-NP:PFPBr was measured using dynamic light scattering (DLS) analysis (DLS-7000, Otsuka Electronics). For DLS measurement, the scattering angle was fixed at 135°, and the temperature of the sample was kept constant at 25.0°C ± 0.1°C. In the case of ZnO-NP:KBr and ZnO-NP:PFPBr solutions, KBr and PFPBr were first dissolved in 2-methoxyethanol (2-ME) to prepare KBr and PFPBr solutions of various concentrations, respectively. After sufficient stirring, various amounts of KBr and PFPBr 2-ME solutions were added to the ZnO-NP IPA (isopropyl alcohol) dispersion and mixed for 12 hours, with a total concentration of about 8 mg/mL to about 10 mg/mL, respectively. ZnO-NP:KBr and ZnO-NP:PFPBr solutions were obtained. To control the concentration of the mixed solution, pure IPA was added to the mixed solution.

XPS analysis

XPS experiments were performed using an XPS spectrometer (K-alpha+, Thermo Scientific) equipped with a fine-focus monochromator Al Kα at hν = 1,486.6 eV. ZnO-NP, ZnO-NP:KBr, and ZnO-NP:PFPBr thin films were prepared by spin casting each solution on a silicon substrate cleaned with UV ozone. Afterwards, the thin film was annealed at 80°C for 5 minutes in a nitrogen-filled glove box, after which the sample was loaded into an XPS spectrometer and XPS spectra were obtained at a pressure of 5 Х 10 ^-9 mbar.

Light microscopy analysis

Surface images of ZnO-NP, ZnO-NP:KBr, and ZnO-NP:PFPBr films before and after tensile bending were captured using an optical microscope (OM) (LV100NPOL, Nikon).

Atomic force microscopy analysis

The same thin films used for OM analysis were used in the atomic force microscope (AFM) system (AFM5100N, Hitachi), and tapping mode atomic force microscopy was used to capture height images.

bending test

ZnO-NP, ZnO-NP:KBr, and ZnO-NP:PFPBr films were fabricated on transparent polyimide substrates through drop casting or spin casting. Afterwards, the membrane was mounted on a custom bending machine (SNM) and repeatedly bent with various bending radii (r = 0.5 mm to 1.5 mm).

Scanning electron microscopy (SEM) analysis

The surface microstructure and thickness characteristics of ZnO-NP, ZnO-NP:KBr, and ZnO-NP:PFPBr films were evaluated using field emission scanning electron microscopy (FE-SEM, S-4800, Hitachi). . SEM images were obtained at an acceleration voltage of 15 kV.

Device manufacturing and characteristic evaluation

A flexible optical sensor (organic photodetector; OPD) was manufactured by spin casting a PEDOT:PSS (PH1000 grade) electrode on a transparent polyimide substrate. Electrical conductivity and wettability of PEDOT:PSS were increased by adding 5 wt% of DMSO (Dimethyl sulfoxide) and Zonyl FS-300 compound (0.16 wt%) to the PEDOT:PSS solution. The electrodes were baked at 150°C for 10 minutes in ambient air. As a hole transporting layer/electron blocking layer (HTL/EBL), PEDOT:PSS (AI4083 grade) was spin cast onto a PEDOT:PSS/DMSO/Zonyl FS-300 transparent electrode in ambient air. The membrane was baked at 150°C for 15 minutes and then transferred to a nitrogen-filled glove box to deposit a photoactive layer. PM6:Y6 (1:1.2 by weight) chloroform solution with a total concentration of 14 mg/mL was used to spin cast onto PEDOT:PSS (AI4083 grade). As an additive, a small amount (5 μL) of 1-chloronaphthalene (1-CN) was added to the PM6:Y6 solution. Afterwards, on the PM6:Y6 layer, a PFN layer was spin-cast from a methanol solution (0.5 m/mL) containing a small amount of acetic acid (2 μL) for better wettability of the ZnO-NP-based solution on ETL/HBL. . Spin-cast a layer of ZnO-NP, ZnO-NP:KBr (1:0.010 by weight, [ ^Br- ] = 0.6 μM), or ZnO-NP:PFPBr (1:0.025 by weight, [ ^Br- ] = 0.6 μM). Thus, ETL/HBL was formed on the PFN layer. Finally, Ag electrodes (thickness 100 nm) were deposited using a thermal evaporator under high vacuum conditions (approximately 2Х10 ^-6 Torr). The device parameters of the flexible OPD were obtained using a QE measurement system (QuantX-300, Newport).

2-2. result

Multivalent interactions between ZnO-NP and PFPBr

To investigate the effect of ionic interaction between ZnO-NP and MCCE on improving the flexibility of ZnO-NP/MCCE (multicharged conjugated electrolyte) thin films, PFPBr (molecular structure, see Figure 8 a) was designed and synthesized. Figures 1 to 7 show detailed information on the synthesis and characterization of PFPBr. Multicharged PFPBr electrolyte is designed to induce multiple ionic interactions with ZnO-NPs through the formation of Zn ²⁺ -Br ^- -N ⁺ bonds at the interface between ZnO-NPs and MCCE. It has been done. Unlike the single-charged K ⁺ cation in the ZnO-NP:KBr complex, the polyionic interactions between polyionic PFP ⁺ and multiple ZnO-NPs can improve the flexibility of the ZnO-NP:PFPBr thin film. .

DLS measurements of ZnO-NP, ZnO-NP:KBr and ZnO-NP:PFPBr solutions were performed to investigate possible aggregation in the ZnO-NP:PFPBr solution due to the strong ionic interaction between ZnO-NP and PFPBr. did. Figure 8b shows the size distribution and images of ZnO-NPs according to various amounts of KBr or PFPBr compounds. ZnO-NP:KB shows almost the same size distribution, regardless of the amount of KBr in the ZnO-NP:KBr solution, compared to the size distribution of pristine ZnO-NPs (about 15 nm to 50 nm in diameter). However, in contrast, the ZnO-NP:PFPBr solution shows a gradual increase in particle size distribution as the amount of PFPBr increases in the ZnO-NP:PFPBr solution. Accordingly, the turbidity of the ZnO-NP:PFPBr solution gradually increases, which is confirmed by the image of the solution (Figure 8b). On the other hand, the ZnO-NP:KBr solution remained transparent even though the same molar ratio of KBr (i.e., [Br ⁻ ]) was added to the ZnO-NP:KBr solution compared to the ZnO-NP:PFPBr solution. The gradually increasing size distribution and turbidity are due to the ionic interaction between ZnO-NP and PFPBr at the adsorption-desorption equilibrium, considering the unchanged turbidity of the original PFPBr solution at the same concentration used in the ZnO-NP:PFPBr solution. This may be due to the enhanced aggregation of ZnO-NPs due to the action (Figure 9). The gradually increased particle size distribution and turbidity of the ZnO-NP:PFPBr mixture demonstrate the effectiveness of multiion PFPBr to improve the chemical interaction between ZnO-NPs.

Characterization evaluation of ZnO-NP:PFPBr thin film

XPS measurements were performed on ZnO-NP, ZnO-NP:KBr, and ZnO-NP:PFPBr thin films to confirm the ionic interaction between ZnO-NP and PFPBr. Figure 10a shows Br 3d core-level XPS spectra of ZnO-NP:KBr and ZnO-NP:PFPBr thin films with various molar concentrations of KBr and PFPBr, which are the same as DLS measurements. XPS spectra of pristine KBr and PFPBr were also obtained and shown in Figure 10a. The spectrum of KBr is centered at 68.8 eV and 69.8 eV, corresponding to Br 3d _5/2 and Br 3d _3/2 , respectively, at the Br ^- anion bound to the K ⁺ cation (hereinafter referred to as free Br). It represents two combined sub-peaks. The ZnO-NP:KBr mixture shows almost the same spectrum as pristine KBr regardless of the amount of KBr in the ZnO-NP:KBr mixture, but with very small spectra centered at 70.0 eV and 71.0 eV corresponding to Zn ²⁺ -Br ^- . A sub-peak was observed.

In contrast, the ZnO-NP:PFPBr thin film shows a clearly shifted spectrum to higher binding energy compared to that of the pristine PFPBr thin film. The shifted spectrum of ZnO-NP:PFPBr is divided into two bound subtypes of pristine PFPBr centered at 67.2 eV and 68.2 eV, corresponding to Br 3d _5/2 and Br 3d _3/2 (i.e., free Br), respectively. Compared to the peak, there are additional sub-peaks centered around 69.0 eV and 69.8 eV corresponding to Zn ²⁺ -Br ^- ion bonds. Compared to free Br, the area of the subpeak for Zn-Br (i.e., A _Zn-Br /A _{free Br} ) increased as the amount of PFPBr increased to 0.27 μM (corresponding to [Br ⁻ ] = 1.6 μM). , and then gradually decreased as larger amounts of PFPBr were used (Figure 10b). Detailed XPS parameters are listed in Table 1 below. Figure 10 a shows that the Br ^- anion of PFPBr coordinates more effectively with the Zn ²⁺ cation on the ZnO-NP surface compared to the Br ^- anion of KBr, even at a lower molar concentration of PFPBr. Effective coordination between Zn ²⁺ and Br ^- ions forms a Zn ²⁺ -Br ^- -N ⁺ ionic bond at the ZnO-NP:PFPBr interface, allowing ZnO-NPs to have strong interactions through multiionic PFP ⁺ cations as linkers. Do this (c in Figure 10). Since each PFPBr has multiple Zn ²⁺ -Br ^- -N ⁺ ion bonds, PFPBr can retain multiple ZnO-NPs in the ZnO-NP:PFPBr mixture to improve thin film flexibility.

Material	Molar concentration of Br - (μM)	BE at the maximum intensity (eV)				Bromide ratio
		Free Br		Zn-Br		A Zn-Br /A Free Br
		3d 5/2	3d 3/2	3d 5/2	3d 3/2
KBr	-	68.8	69.8	-	-	-
ZnO-NP:KBr	0.3	68.5	69.5	70.0	71.0	0.051
ZnO-NP:KBr	1.6	68.5	69.5	70.0	71.0	0.051
ZnO-NP:KBr	3.2	68.4	69.5	70.0	71.0	0.062
ZnO-NP:KBr	6.4	68.3	69.3	70.0	71.0	0.043
PFPBr	-	67.2	68.2	-	-	-
ZnO-NP:PFPBr	0.3	67.4	68.3	69.0	69.7	1.078
ZnO-NP:PFPBr	1.6	67.4	68.3	69.0	69.8	1.108
ZnO-NP:PFPBr	3.2	67.4	68.3	69.0	69.7	0.919
ZnO-NP:PFPBr	6.4	67.4	68.3	69.0	69.7	0.595

Mechanical properties of ZnO-NP:PFPBr thick film

By investigating and comparing the bending stability of ZnO-NP, ZnO-NP:KBr, and ZnO-NP:PFPBr thick films (thickness about 320 nm to about 450 nm) by repeated tensile bending, solid-state ZnO-NPs The influence of ionic interactions on the mechanical properties of the :PFPBr composite was further investigated. A thick film was prepared by drop casting ZnO-NP, ZnO-NP:KBr, and ZnO-NP:PFPBr solutions on a transparent polyimide substrate (100 μm thick). The thick film was repeatedly bent at various bending radii (r), and the surface of the thick film before and after repeated bending was examined using an optical microscope. Figure 11 shows optical microscopy images of ZnO-NP, ZnO-NP:KBr, and ZnO-NP:PFPBr thick films after five tensile bending at r = 1.5 mm. ZnO-NP and ZnO-NP:KBr thick films mostly show a greater number of cracks in the direction perpendicular to the bending direction. In contrast, the ZnO-NP:PFPBr thick film exhibited a smooth and continuous surface without cracking even after applying the same mechanical stress, resulting from the strong intermolecular interactions of Zn ²⁺ -Br ^- -N ⁺ coordination described above. It shows the improved flexibility of the thick film.

Surface changes between thick films were further investigated through SEM measurements (FIG. 12). Similar to the optical microscopy results, many cracks were observed on the surface of the ZnO-NP and ZnO-NP:KBr thick films. However, the ZnO-NP:PFPBr thick film showed an intact surface without cracks even after applying the same bending conditions, and no small cracks were observed even at higher magnifications. Considering the relatively large thickness of the ZnO-NP:PFPBr thick film (g to i in Figure 12), which is disadvantageous for thin film flexibility, the significantly improved mechanical flexibility of the ZnO-NP:PFPBr thick film is superior to the mechanically robust ZnO-NP:PFPBr film. shows the effect of polyion PFPBr on

In particular, the surface morphology of the ZnO-NP:PFPBr thick film is different from that of the ZnO-NP and ZnO-NP:KBr thick films. The relatively rough surface of the ZnO-NP:PFPBr thick film compared to the ZnO-NP and ZnO-NP:KBr thick films may be due to the ZnO-NP having less mobility due to ionic interaction with PFPBr during the drying process of the film. There is (j in Figure 12). The multivalent interaction between ZnO-NPs and PFPBr may reduce the degree of freedom of ZnO-NPs during the film drying process, resulting in many aggregation sites and associated rough surfaces. Additionally, AFM images confirm cracks (for ZnO-NP and ZnO-NP:KBr thick films) and rough surface morphology (for ZnO-NP:PFPBr thick films) as described above (Figure 13). The results show that effective ionic interaction between ZnO-NPs and PFPBr; and the improved mechanical flexibility of the ZnO-NP:PFPBr membrane.

Mechanical properties of ZnO-NP:PFPBr thin films

ZnO-NP:PFPBr thin film (thickness 55 nm to 60 nm) also had improved flexibility compared to ZnO-NP and ZnO-NP:KBr thin films (FIG. 14). Thin films were prepared by spin casting ZnO-NP, ZnO-NP:KBr, and ZnO-NP:PFPBr solutions on a transparent polyimide substrate. Since the film thickness of the thin film is much smaller than that of the thick film (FIG. 12g to i), no large cracks are observed in the thin film by optical microscopy measurements. Therefore, SEM measurements were performed to find small cracks on the thin film surface. Similar to thick films, ZnO-NP and ZnO-NP:KBr thin films exhibit small but numerous cracks after tensile bending. The ZnO-NP:KBr thin film appears to have a relatively small number of cracks compared to the ZnO-NP thin film (a to b in Figure 14), but a greater number of cracks was observed at high magnification (1Х10 ⁵ ) (e in Figure 14). In contrast, the ZnO-NP:PFPBr thin film shows no cracks after tensile bending under the same bending conditions (r = 1.5 mm) compared to the ZnO-NP and ZnO-NP:KBr thin films even at high magnification (Figure 14c and f). .

Flexible optical sensor (flexible organic photodetector; flexible OPD)

By fabricating a flexible OPD on a transparent polyimide substrate using ZnO-NP:PFPBr as an electron transport layer/hole blocking layer (ETL/HBL), improved mechanical flexibility of the ZnO-NP:PFPBr thin film was achieved. It was used. For comparison, flexible devices using ZnO-NP and ZnO-NP:KBr thin films were also fabricated. Figures 15a and b respectively show the device structure and corresponding energy level diagram. In particular, PFN was used to improve the wettability of the ZnO-NP-based solution when casting ZnO-NP-based ETL/EBL. Afterwards, some devices were subjected to tensile bending at r = 2.5 mm in a nitrogen-filled glovebox (Figure 15c). Figure 15 d and e show the responsivity (R) and detectability (detectivity (D ^* )) spectra of flexible OPDs made of various ETL/HBL before and after 250 repeated bendings, where the data are shown under short circuit conditions (short circuit). -circuit condition) (0 V). The corresponding external quantum efficiency (EQE) spectrum is shown in Figure 16.

The original device showed a similar EQE spectrum regardless of the type of ETL/HBL, with a value of approximately 69% or higher in the spectrum at 750 nm. However, after bending 250 times at r = 2.5 mm, the EQE of the device made of ZnO-NP decreased by about 46.4%. The EQE of the device containing ZnO-NP:KBr decreased significantly in the entire spectral range after 250 repeated bending cycles. In contrast, the ZnO-NP:PFPBr-based OPD showed an almost unchanged EQE spectrum compared to the pristine device even after bending under the same conditions (250 times at r = 2.5 mm).

Therefore, the R and D ^* of flexible OPDs fabricated from ZnO-NP and ZnO-NP:KBr ETL/HBL decreased significantly after 250 bendings at r = 2.5 mm, while the ZnO-NP:PFPBr devices were almost the same before and after bending. The R spectrum was shown (d in Figure 15). As shown in Table 2 below, the R of the ZnO-NP and ZnO-NP:KBr devices was 0.23 A/W and 0.22 A/W, corresponding to a decrease of 45.2% and 47.6%, respectively, after 250 bendings at r = 2.5 mm. decreased. Meanwhile, the D ^* values decreased to 2.28 Х 10 ¹² Jones and 2.25 Х 10 ¹² Jones, respectively, which corresponds to a reduction of 46.3% and 44.2% compared to the original device (D ^* = 4.25 Х 10 ¹² Jones and 4.03 Х, respectively) 10 ¹² Jones). In contrast, R and D ^* of the ZnO-NP:PFPBr device after the same bending test were found to be 0.38 A/W and 3.62 Х 10 ¹² Jones, respectively. These values decreased by only 7.3% and 10.0%, respectively, compared to the performance of the original device before bending (R = 0.41 A/W and D ^* = 4.02 Х 10 ¹² Jones).

The significant performance degradation of ZnO-NP and ZnO-NP:KBr devices is due to cracks generated in the ETL/cathode layer by the applied tensile stress. Cracks created on the ZnO-NP/Ag and ZnO-NP:KBr/Ag layers in flexible OPD were confirmed by optical microscopy images, and ZnO-NP:PFPBr/Ag shows a smooth surface without visible cracks (Figure 15). f). OPD performance was reduced due to poor electron collection seen in cracks, which could increase the electrical resistance to longitudinal electron transport and prevent efficient contact at the photoactive/ETL/cathode interface. This reduces the internal electric field near the crack area. These results were consistent with the optical microscopy, SEM, and AFM results described above, and indicated that the mechanical flexibility of the ZnO-NP:PFPBr thin film was greatly improved through effective ionic coordination and strong molecular interactions between ZnO-NP and PFPBr.

ETL/HBL	Bending cycles @r=2.5 mm	R@λ=750 nm (A/W)	D * @λ=750 nm (×10 12 , Jones)
ZnO-NPs	-	0.42	4.25
	250	0.23	2.28
ZnO-NP:KBr	-	0.42	4.03
	250	0.22	2.25
ZnO-NP:PFPBr	-	0.41	4.02
	250	0.38	3.62

In the present invention, the ionic interaction between ZnO-NP and polyionic PFPBr electrolyte and the effect of this interaction on the mechanical properties of ZnO-NP:PFPBr thin films were investigated. Based on a diphenylfluorene-based backbone, PFPBr with multiple pyridinium bromides as ionic pendant groups was synthesized. The multiple ionic pendant groups of the ZnO-NP:PFPBr complex form multiple Zn ²⁺ -Br ^- -N ⁺ coordinations by a single PFPBr molecule. Therefore, the polyionic PFP ⁺ cation can have multiple ZnO-NPs through ionic coordination between ZnO-NPs and PFPBr. In contrast, in the ZnO-NP:KBr complex, KBr with a single K ⁺ cation cannot have multiple ZnO-NPs due to inefficient coordination of the Zn ²⁺ -Br ^- -K ⁺ bond. Additionally, a single K ⁺ cation cannot have multiple ZnO-NPs despite the Zn ²⁺ -Br ^- -K ⁺ coordination on the ZnO-NP surface, as each K ⁺ cation can have one ZnO-NP. Therefore, the mechanical flexibility of the ZnO-NP:PFPBr thin film is greatly improved, while the ZnO-NP and ZnO-NP:KBr thin films become brittle under repeated tensile bending stress. This was confirmed through optical microscopy, SEM, and AFM investigations.

Flexible OPD is fabricated due to the mechanically robust ZnO-NP:PFPBr thin film developed in the present invention. Even after 250 repeated bending cycles at r = 2.5 mm, flexible OPDs fabricated using ZnO-NP:PFPBr ETL/HBL on transparent polyimide substrates exhibit high R and D ^* values of 0.38 A/W and 3.62 Х10 ¹² Jones, respectively. It showed very stable performance. These values are almost similar to those of the original device before bending (R = 0.41 A/W and D ^* = 4.02 Х 10 ¹² Jones). In contrast, the OPD containing ZnO-NP and ZnO-NP:KBr showed a significant decrease in R and D ^* compared to the pristine device before bending due to crack formation in the ZnO-NP and ZnO-NP:KBr ETL/HBL. . Considering that PFPBr does not change the electrical properties of ZnO-NP:PFPBr thin films, the present invention presents a simple and effective strategy to improve the mechanical properties of metal oxide nanoparticle-based thin films, and provides a simple and effective strategy for improving the mechanical properties of metal oxide nanoparticle-based thin films and improves the mechanical properties of metal oxide nanoparticles developed to date. The particles can be used in various flexible organic optoelectronic devices.

The description of the present application described above is for illustrative purposes, and those skilled in the art will understand that the present application can be easily modified into other specific forms without changing its technical idea or essential features. Therefore, the embodiments described above should be understood in all respects as illustrative and not restrictive. For example, each component described as single may be implemented in a distributed manner, and similarly, components described as distributed may also be implemented in a combined form.

The scope of the present application is indicated by the claims described below rather than the detailed description above, and all changes or modified forms derived from the meaning and scope of the claims and their equivalent concepts should be construed as being included in the scope of the present application. .

Claims (12)

1. A dendrimer containing at its terminal a compound represented by the following formula (I), an oligomer represented by the following formula (II), or a compound represented by the following formula (I); and

   zinc oxide nanoparticles

   Flexible membrane comprising:

   [Formula Ⅰ]

   

   ;

   [Formula Ⅱ]

   

   ;

   In Formula I and Formula II,

   R ¹ is hydrogen or -OR ^a -R ^b ,

   R ^a is a C _1-10 alkylene group,

   R ^b is an ammonium halide salt, and the ammonium salt is an ammonium salt (-NH ₃ ⁺ ), a C _1-20 primary alkylamine, a secondary alkylamine, or a tertiary alkylamine containing at least one nitrogen, C _3-10 It is an ammonium salt of a heterocycloalkyl group, or a C _3-10 heteroaryl group, and in the ammonium halide salt, the halide ion is F ^- , Cl ^- , Br ^- , or I ^- ,

   However, except for the case where R ¹ is all hydrogen,

   R ² is

   

   ,

   

   ,

   

   ,

   

   ,

   

   , or

   

   ego,

   m is 0 or 1, n is an integer from 1 to 10,

   The dashed line is the connection part.
2. According to claim 1,

   The ammonium salt of R ^b is ammonium salt (-NH ₃ ⁺ ), trimethylammonium salt, triethylammonium salt, tripropylammonium salt, Methylammonium salt, ethyl ammonium salt, propyl ammonium salt, dimethyl ammonium salt, ethyl methyl ammonium salt, methyl propy ammonium salt, diethy ammonium salt, ethyl propy ammonium salt, dipropylammonium salt, ethyl dimethyl ammonium salt, dimethyl propy ammonium salt, diethyl methyl ammonium salt, ethyl methyl propy ammonium salt, Select from methyldipropylammonium salt, diethylpropylammonium salt, ethyldipropylammonium salt, pyridinium salt, aziridinium salt, azetidinium salt, pyrrolidinium salt, piperidinium salt, azepanium salt, azocenium salt, and imidazolium salt. A flexible membrane comprising one or more
3. According to claim 1,

   The R ¹ is

   

   It is a flexible membrane.
4. According to claim 1,

   A flexible membrane wherein the compound represented by Formula I is diphenylfluorene pyridinium bromide represented by the following Formula 1:

   [Formula 1]

   

   .
5. According to claim 1,

   The oligomer represented by Formula II is a flexible membrane represented by the following Formula 2:

   [Formula 2]

   

   ;

   In Formula 2,

   R ² is

   

   ,

   

   ,

   

   ,

   

   ,

   

   , or

   

   ego,

   m is 0 or 1, n is an integer from 1 to 10,

   The dashed line is the connection part.
6. According to claim 1,

   The dendrimer is a flexible membrane of polyethyleneimine (PEI), polypropyleneimine (PPI), or polyamidoamine (PAMAM).
7. According to claim 1,

   A flexible membrane in which the zinc oxide nanoparticles are aggregated by coordination between the halide ion of R ^b and Zn ²⁺ of the zinc oxide nanoparticles.
8. According to claim 1,

   A flexible membrane in which the diameter of the zinc oxide nanoparticles is 1 nm to 100 nm.
9. According to claim 1,

   The flexible membrane has a thickness of 1 nm to 1 μm.
10. According to claim 1,

    The flexible membrane is a flexible membrane that does not crack even if bent more than 300 times at a bending radius of 2.5 mm in a thickness range of 100 nm or less.
11. A flexible electronic device comprising the flexible film according to claim 1 as a charge transfer layer.
12. According to claim 11,

    The flexible electronic device is a flexible film comprising one or more selected from flexible organic light-emitting diodes, flexible solar cells, flexible optical sensors, perovskite light-emitting diodes, flexible transistors, and flexible chemical sensors.

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