Photodetector comprising organic polymer-quantum dot composite light-absorbing layer and manufacturing method therefor

Abstract

One embodiment of the present invention provides a photodetector comprising a light-absorbing layer that is formed between an upper electrode and a lower electrode and contains a fluorine-based organic polymer and colloidal quantum dots. According to the embodiment, using the newly proposed light-absorbing layer enables reducing surface defects of the quantum dots in the photodetector while simultaneously improving operational stability.

Description

Photodetector comprising an organic polymer-quantum dot composite light absorption layer and a method for manufacturing the same

[0001] The present invention relates to a photodetector and a method for manufacturing the same, and more specifically, to a photodetector comprising a light absorption layer and a method for manufacturing the same.

[0002]

[0003] The infrared band plays a crucial role in various applications due to its longer wavelength than visible light, low energy, and low atmospheric scattering characteristics. These properties offer potential for use in multiple fields, ranging from infrared imaging and remote sensing to communications, medical imaging, and autonomous driving technology. The development of photodetectors that operate effectively in the infrared band is considered a key factor in the commercialization and performance enhancement of these technologies.

[0004] Conventional infrared photodetectors often rely on silicon-based semiconductor technology; despite their excellent performance, this technology is characterized by high costs, complex fabrication processes, and limited sensitivity in specific wavelength bands. To address these limitations, the development of light-absorbing layers combining colloidal quantum dot materials and organic polymers is garnering attention.

[0005]

[0006] Meanwhile, photodiode-based photodetector structures generate photocurrent through a multilayer structure consisting of a bottom electrode, an electron transport layer, a light absorption layer, a hole transport layer, and a top electrode. However, quantum dot-based light absorption layers used in conventional technology had disadvantages such as surface defects and reduced operational stability. In particular, halogen-based ligands are prone to detaching from the surface under electrical or thermal stress environments, degrading the stability and performance of quantum dots; furthermore, there was a problem where thin film damage was likely to occur due to polar solvents during additional coating processes.

[0007] Therefore, the development of a light-absorbing layer equipped with high absorption efficiency in the infrared band, minimized surface defects, and operational stability, as well as a photodetector utilizing the same, remains an important technical challenge to overcome the limitations of existing technologies.

[0008]

[0009] The present invention is proposed to solve the aforementioned conventional problems and aims to provide a new composite light-absorbing layer utilizing a fluorine-based organic polymer and colloidal quantum dots, which has high absorption efficiency in the infrared band while minimizing surface defects and ensuring driving stability.

[0010] In addition, the objective of the present invention is to provide a light-absorbing layer capable of forming a uniform and stable thin film by maximizing the quantum confinement effect while solving the problem of surface ligand detachment, thereby increasing resistance to oxidation and external impurities, and preventing damage caused by polar solvents, and a high-performance infrared photodetector utilizing the same.

[0011] In addition, the objective of the present invention is also to provide a method for manufacturing such a photodetector.

[0012] However, the purpose of the present invention is not limited to the purpose described above, and all of the inventor's intentions regarding the subject to be demonstrated through each of the embodiments proposed thereafter constitute the purpose of the present invention.

[0013]

[0014] According to one embodiment of the present invention, a photodetector may be provided comprising a light absorption layer comprising a fluorine-based organic polymer and colloidal quantum dots between an upper electrode and a lower electrode.

[0015] The above colloidal quantum dots can control the absorption range through a quantum confinement effect that can control the band gap at a specific size, and can control solubility and electrical properties by adjusting surface ligands.

[0016] The light absorption layer described above can be configured to absorb light in the infrared band.

[0017] The above colloidal quantum dots may be composed of crystal particles with a size of 3 nm or more.

[0018] The above organic polymer may be composed of a fluorine-based organic polymer.

[0019] The light absorption layer can be formed so that the maximum absorption peak is located in the wavelength range of 1100 nm to 1550 nm.

[0020] The thickness of the light absorption layer can be configured to be 100 nm to 500 nm.

[0021] The above colloidal quantum dots are composed of group IV-VI quantum dots including PbS, PbSe and PbTe, and may have a band gap energy of 0.7 eV to 1.3 eV.

[0022] Between the lower electrode and the light absorption layer, an electron transport layer comprising zinc oxide (ZnO) and having a thickness of 20 nm to 50 nm may be included.

[0023] Between the light absorption layer and the upper electrode, a hole transport layer may be included that includes nickel oxide (NiOx) and molybdenum oxide (MoOx), etc., and has a thickness of 20 nm to 100 nm.

[0024] The lower electrode is formed with a thickness of 70 nm to 120 nm and may include indium tin oxide (ITO), and the upper electrode is formed with a thickness of 50 nm to 200 nm and may be composed of metals such as gold (Au), silver (Ag), aluminum (Al), and titanium (Ti).

[0025]

[0026] According to another embodiment of the present invention, a method for manufacturing a photodetector may be provided, comprising the steps of forming an electron transport layer on a lower electrode, forming an organic polymer-quantum dot composite light absorption layer thereon, then forming a hole transport layer, and then forming an upper electrode.

[0027] The above quantum dot light absorption layer can be synthesized using group IV-VI quantum dots, mixed with a ligand-substituted precursor solution to improve conductivity, and then reacted with a fluorine-based organic polymer.

[0028] The above-described photodetector may include an organic polymer-quantum dot composite light absorption layer having high absorption efficiency in the infrared band between the upper electrode and the lower electrode.

[0029]

[0030] According to one embodiment of the present invention, it is possible to realize a photodetector that minimizes defects on the surface of quantum dots and improves resistance to oxidation and external impurities through a composite light-absorbing layer comprising colloidal quantum dots and a fluorine-based organic polymer.

[0031] In addition, the quantum dot composite light absorption layer according to one embodiment of the present invention has the effect of being able to operate stably for a long time by physically suppressing ligand desorption that may occur when an external voltage is applied.

[0032] In addition, according to one embodiment of the present invention, a composite light-absorbing layer utilizing a fluorine-based organic polymer is proposed to ensure resistance to polar solvents, thereby enabling the formation of a uniform thin film and reducing noise caused by thin film damage.

[0033] In addition, according to one embodiment of the present invention, by optimizing the bandgap of the quantum dots and the thickness of the composite, the infrared light absorption efficiency in the 1100 nm to 1550 nm band can be maximized.

[0034] In addition, according to one embodiment of the present invention, a photodetector based on a composite light-absorbing layer maintains high performance even at low driving voltages and has the effect of providing high sensitivity and long-term reliability.

[0035] However, the effects of the present invention are not limited to those described above, but include all effects naturally realized through the various configurations proposed in the present invention.

[0036]

[0037] Figure 1 is a schematic diagram showing the physical ligand desorption inhibition mechanism and defect state control mechanism of a light absorption layer containing organic polymers and colloidal quantum dots.

[0038] FIG. 2 is a schematic diagram showing the structure of a photodetector including an organic polymer-quantum dot composite light absorption layer according to one embodiment of the present invention.

[0039] Figure 3 is a photograph showing the experimental results of confirming the degree of damage when a polar solvent was dropped onto a quantum dot-polymer composite according to one embodiment of the present invention and a commercially available thin film corresponding to a control group.

[0040] Figure 4 is a graph showing the effect of reducing dark current in an environment where a reverse bias voltage is applied after multiple driving voltage sweeps of a photodetector fabricated from a quantum dot-polymer composite according to one embodiment of the present invention.

[0041]

[0042] The embodiments of the present invention are illustrative for the purpose of explaining the technical concept of the present invention. The scope of rights according to the present invention is not limited to the embodiments presented below or the specific description thereof.

[0043] All technical and scientific terms used in this invention, unless otherwise defined, have the meaning generally understood by those skilled in the art to which this invention pertains. All terms used in this invention are selected for the purpose of further explaining this invention and are not selected to limit the scope of rights according to this invention.

[0044] Expressions such as "comprising," "having," "having," etc. used in the present invention should be understood as open-ended terms implying the possibility of including other embodiments, unless otherwise stated in the phrase or sentence containing such expressions.

[0045] Unless otherwise stated, singular expressions described in the present invention may include the meaning of the plural form, and this applies likewise to singular expressions described in the claims.

[0046] Hereinafter, each embodiment of the present invention will be described in detail through the drawings of the present invention and experiments containing the inventors' intentions.

[0047]

[0048] In one embodiment of the present invention, an infrared light absorption layer manufactured based on a solution process and a photodetector utilizing the same are introduced. The light absorption layer is manufactured by mixing a fluorine-based organic polymer with colloidal quantum dots, and a photodetector utilizing the same is described in detail.

[0049] Figure 1 is a schematic diagram showing the physical ligand desorption inhibition mechanism and defect state control mechanism of a light absorption layer including the organic polymer and colloidal quantum dots described above.

[0050] Figure 1 illustrates a phenomenon in which fluorine-based organic polymer chains are located on the surface of quantum dot particles in the light absorption layer described above, and fluorine inhibits the process of affecting other particles even when ligands on the surface of quantum dot particles are detached. Through this, the stability of the light absorption layer is improved, and the fluorine also performs the role of supplying electrons to cation elements that are not bound to ligands, thereby controlling the defect state and inhibiting oxidation.

[0051] FIG. 2 is a schematic diagram showing the structure of a photodetector including an organic polymer-quantum dot composite light absorption layer according to one embodiment of the present invention.

[0052] The stacked structure of the photodetector shown in Fig. 2 is similar to that of a conventional photodetector, but in one embodiment of the present invention, a special effect can be achieved by configuring the light absorption layer to include the organic polymer and colloidal quantum dots described above.

[0053] According to the above embodiment, by using the newly proposed light absorption layer, surface defects of quantum dots in a photodetector can be reduced while simultaneously improving driving stability.

[0054]

[0055] In one embodiment of the present invention, a photodetector is provided comprising a light absorption layer including an organic polymer and a colloidal quantum dot formed between an upper electrode and a lower electrode.

[0056] The above organic polymer may be a fluorine-based organic polymer. The above fluorine-based organic polymer can contribute to suppressing oxidation and interaction with external impurities by providing electrons to the surface of the quantum dot.

[0057] Such interactions between quantum dots and polymers alter solubility when forming a composite, thereby ensuring solvent orthogonality when forming a thin film through coating. This has the effect of enabling the fabrication of a uniform thin film with minimal damage caused by solvents of different polarities.

[0058] In one embodiment, the fluorine-based organic polymer may include PVDF (Poly(vinylidene fluoride)). Additionally, the fluorine-based organic polymer may additionally include a copolymer such as PVDF-TrFE (Poly(vinylidene fluoride-co-trifluoroethylene)), a polymer such as PCTFE (Polychlorotrifluoroethylene), or PTFE (Polytetrafluoroethylene). As shown in FIG. 1, the fluorine groups in these polymers can contribute to increasing resistance to oxidation and impurities by enhancing the electron-donating ability of the quantum dot surface.

[0059]

[0060] According to one embodiment of the present invention, the light absorption layer absorbs light in the infrared band and can be utilized over a wide spectral range.

[0061] The quantum dots included in the light absorption layer above are synthesized to a specific size, so that the absorption performance in the infrared band (1100 nm to 1550 nm) can be adjusted.

[0062]

[0063] According to one embodiment of the present invention, the colloidal quantum dots may include crystal particles having a size of 3 nm or more.

[0064] The size of the above quantum dots can have a direct effect on the light absorption band and efficiency. Quantum dots with a size of 3 nm or larger provide a quantum confinement effect and have the potential to optimize absorption characteristics in the infrared band. However, crystals of a large size of about 3 nm or larger may present a problem where sufficient surface control is difficult using only conventional halogen ligands. In consideration of this, the present invention may include a fluorine-based organic polymer in the light absorption layer together with colloidal quantum dots.

[0065] According to one embodiment of the present invention, the light absorption layer may have a maximum absorption peak in the wavelength range of 1100 nm to 1550 nm.

[0066] The above maximum absorption peak range may be set for efficient light detection in the infrared band. The above maximum absorption peak range may be adjusted according to the material and size of the quantum dots included in the light absorption layer.

[0067]

[0068] According to one embodiment of the present invention, the light absorption layer may be formed with a thickness of 100 nm to 500 nm. The thickness of the light absorption layer may be an important factor in maintaining a balance between light absorption efficiency and charge extraction performance. The light absorption layer may preferably be formed with a thickness of 250 nm to 500 nm. If the thickness is less than 250 nm, sufficient light absorption in the infrared band may not occur, and if it exceeds 500 nm, a problem may arise in which the charge extraction efficiency due to internal potential is reduced.

[0069]

[0070] According to one embodiment of the present invention, the quantum dots may be composed of group IV-VI quantum dots including PbS, PbSe, and PbTe, and may have a bandgap energy of 0.7 eV to 1.3 eV. Group IV-VI quantum dots such as PbS and PbSe may provide optimal absorption characteristics in the aforementioned wavelength band. Additionally, the bandgap energy is set to provide absorption efficiency and conductivity characteristics in the infrared band and may be adjusted according to the size and material of the quantum dots.

[0071]

[0072] According to one embodiment of the present invention, an electron transport layer may be further included between the lower electrode and the light absorption layer, and the electron transport layer may have a thickness of 20 nm to 50 nm and may include zinc oxide (ZnO).

[0073] The electron transport layer is a component for efficiently transporting electrons to electrodes, and zinc oxide (ZnO) is a widely used electron transport layer material capable of providing high electrical conductivity and excellent light transmittance. In addition to zinc oxide, any various materials known to be applicable to electron transport layers are included within the scope of the present invention. For example, one or more materials selected from titanium oxide, indium tin oxide (ITO), aluminum oxide, and organic electron transport materials may be used in the electron transport layer according to the embodiments of the present invention.

[0074] If the thickness of the electron transport layer is less than 20 nm, noise caused by dark current may increase, and if it exceeds 50 nm, a problem of reduced conductivity may occur.

[0075]

[0076] According to one embodiment of the present invention, a hole transport layer may be further included between the light absorption layer and the upper electrode, wherein the hole transport layer has a thickness of 20 nm to 100 nm and nickel oxide (NiO₂) x ) and molybdenum oxide (MoOx It may include ).

[0077] The hole transport layer is located on the opposite side of the electron transport layer with respect to the light absorption layer and is a layer for effectively transporting holes. The hole transport layer is nickel oxide (NiO₂). x ) and molybdenum oxide (MoO x Metal oxides such as ) can be used. In addition, vanadium oxide, tungsten oxide, etc. can also be cited as examples. In addition to metal oxides, the hole transport layer may include conductive polymers such as PEDOT:PSS. The metal oxide can provide high stability and conductivity characteristics. The thickness of the metal oxide can be set by considering the balance between hole transport efficiency and layer stability, and can be formed with a thickness of 20 nm to 100 nm.

[0078] According to one embodiment of the present invention, the lower electrode may have a thickness of 70 nm to 120 nm and may include ITO (Indium Tin Oxide). ITO is widely used as a transparent electrode and can provide both light transmittance and conductivity.

[0079] In addition, according to one embodiment of the present invention, the upper electrode has a thickness of 50 nm to 200 nm and may comprise gold, silver, aluminum, or titanium. The metals used as the upper electrode provide high conductivity and stability and can be selected according to a specific application.

[0080]

[0081] According to another embodiment of the present invention, a method for manufacturing a photodetector may be provided, comprising the steps of forming an electron transport layer on a lower electrode, forming an organic polymer-quantum dot composite light absorption layer thereon, then forming a hole transport layer, and then forming an upper electrode.

[0082] According to the manufacturing method proposed in the above embodiment, after the synthesis of colloidal quantum dots, a process may be performed to replace the long organic ligands surrounding the surface with short ligands to improve electrical conductivity. Subsequently, an ink may be prepared by mixing an organic polymer with the ligand-substituted quantum dots and coating the resulting layer to produce a light-absorbing layer.

[0083] At this time, the quantum dot light absorption layer is synthesized using group IV-VI quantum dots and can be prepared by mixing with the ligand-substituted precursor solution to improve conductivity and then reacting with a fluorine-based organic polymer.

[0084] The above-described photodetector may include an organic polymer-quantum dot composite light absorption layer having high absorption efficiency in the infrared band between the upper electrode and the lower electrode.

[0085]

[0086] <Example>

[0087] The following describes the manufacturing process of a photodetector including the light absorption layer described above, which was produced by the inventors through repeated experiments.

[0088] First, a glass substrate was prepared with a bottom electrode made of indium-tin oxide (ITO) with a thickness of 70 nm to 120 nm.

[0089] Next, an electron transport layer was coated in an ink state on the lower electrode. The electron transport layer was coated using zinc oxide (ZnO) prepared by the sol-gel method or in the form of nanoparticles. At this time, the thickness of the electron transport layer was formed to be 20 nm to 50 nm.

[0090] After coating the electron transport layer, a quantum dot light absorption layer was coated on top of the electron transport layer. The quantum dot light absorption layer was prepared with a thickness of 250 nm to 500 nm, and the maximum absorption peak was formed in the wavelength range of 1100 nm to 1550 nm.

[0091] For the above quantum dot light absorption layer, group IV-VI quantum dots such as PbS, PbSe, and PbTe and materials with a band gap between 0.7 and 1.3 eV were used.

[0092] Afterwards, to improve the conductivity of the quantum dots immediately after synthesis, a solution in which lead iodide (PbI2) was dissolved in dimethylformamide (DMF) at a concentration of 0.1 M to 0.5 M, lead bromide (PbBr2) at a concentration of 0.01 M to 0.1 M, and sodium acetate (NaOAc) at a concentration of 0.01 M to 0.1 M was mixed with a solution in which quantum dots were dissolved in n-octane at a concentration of 1 mg / ml to 10 mg / ml as ligand-substituted precursors and reacted.

[0093] After drying the above-described reacted quantum dot material, it was mixed with poly(vinylidene fluoride), PVDF, dissolved in DMF at a concentration of 0.5 mg / ml to 5 mg / ml and reacted. At this time, when the concentration of PVDF was 0.5 mg / ml or less, a problem occurred in which the organic polymer did not sufficiently interact with the surface of the quantum dots. When the concentration of PVDF was 5 mg / ml or more, a problem occurred in which the conductivity of the photodiode could decrease due to the large amount of organic polymer.

[0094] A hole transport layer was fabricated on top of it with a thickness of approximately 20 nm to 100 nm. The material of the hole transport layer was nickel oxide (NiO₂). x ), molybdenum oxide (MoO₂) xIt was fabricated using a p-type semiconductor material with a band gap between 1.1 and 1.5 eV, which is substituted with a ligand such as metal oxides such as ) or 1,2-ethanedithiol (EDT).

[0095] Subsequently, a metal electrode such as gold (Au), silver (Ag), aluminum (Al), or titanium (Ti) was fabricated on top of the hole transport layer by thermal evaporation to a thickness of 50 nm to 200 nm. Through this, a photodetector was completed, and the effects according to the embodiments of the present invention described above were confirmed through experiments.

[0096]

[0097] Figure 3 is a photograph showing the experimental results of confirming the degree of damage when a polar solvent was dropped onto a quantum dot-polymer composite according to one embodiment of the present invention and a commercially available thin film corresponding to a control group.

[0098] Through this, it can be confirmed that when a light absorption layer is formed with a quantum dot-polymer composite according to the above-described embodiment, resistance to polar solvents is increased, making it possible to implement a stable photodetector.

[0099]

[0100] Figure 4 is a graph showing the effect of reducing dark current in an environment where a reverse bias voltage is applied after multiple driving voltage sweeps of a photodetector fabricated from a quantum dot-polymer composite according to one embodiment of the present invention.

[0101] It can be confirmed that the dark current is reduced by the mechanism shown in Fig. 1 through a relatively low dark current at the reverse bias voltage compared to the control group after multiple voltage sweeps in Fig. 4, thereby ensuring electrical stability in the driving environment of the photodetector.

[0102]

[0103] The foregoing description is merely an illustrative explanation of the technical concept of the present invention, and those skilled in the art to which the present invention pertains may make various modifications and variations within the scope of the essential characteristics of the present invention. Accordingly, the embodiments disclosed in the present invention are intended to explain, not limit, the technical concept of the present invention, and the scope of the technical concept of the present invention is not limited by these embodiments. The scope of protection of the present invention shall be interpreted by the claims below, and all technical concepts within an equivalent scope shall be interpreted as being included within the scope of rights of the present invention.

Claims

1. Formed between the upper electrode; and the lower electrode; A light absorption layer comprising an organic polymer and colloidal quantum dots; comprising, The above organic polymer comprises a fluorine-based organic polymer, A photodetector comprising an organic polymer-quantum dot composite light absorption layer.

2. In Paragraph 1, The above light absorption layer is, absorbing light in the infrared band, A photodetector comprising an organic polymer-quantum dot composite light absorption layer.

3. In Paragraph 1, The above colloidal quantum dots are crystalline particles with a size of 3 nm or more, A photodetector comprising an organic polymer-quantum dot composite light absorption layer.

4. In Paragraph 1, The above organic polymer is a fluorine-based organic polymer, A photodetector comprising an organic polymer-quantum dot composite light absorption layer.

5. In Paragraph 1, The light absorption layer has a maximum absorption peak in the wavelength range of 1100 nm to 1550 nm. A photodetector comprising an organic polymer-quantum dot composite light absorption layer.

6. In Paragraph 1, The light absorption layer has a thickness of 100 nm to 500 nm. A photodetector comprising an organic polymer-quantum dot composite light absorption layer.

7. In Paragraph 1, The above quantum point is, It is a group IV-VI quantum dot including PbS, PbSe, and PbTe, and Having a bandgap energy of 0.7 eV to 1.3 eV, A photodetector comprising an organic polymer-quantum dot composite light absorption layer.

8. In Paragraph 1. The electron transport layer between the lower electrode and the light absorption layer is further included, The above electron transport layer is, A thickness of 20 nm to 50 nm comprising zinc oxide (ZnO), A photodetector comprising an organic polymer-quantum dot composite light absorption layer.

9. In Paragraph 1, It further includes a hole transport layer between the light absorption layer and the upper electrode, The above hole transport layer is, It has a thickness of 20 nm to 100 nm and nickel oxide (NiO x ) and molybdenum oxides (MoO₂) x ) comprising a metal oxide or p-type semiconductor material A photodetector comprising an organic polymer-quantum dot composite light absorption layer.

10. In Paragraph 1, The lower electrode has a thickness of 70 nm to 120 nm and comprises ITO, The upper electrode has a thickness of 50 nm to 200 nm and comprises a metal including gold, silver, aluminum, and titanium. A photodetector comprising an organic polymer-quantum dot composite light absorption layer.

11. A step of forming an electron transport layer on the lower electrode; A step of forming a light absorption layer on the electron transport layer; A step of forming a hole transport layer on the quantum dot light absorption layer; and The method includes the step of forming an upper electrode on the hole transport layer; The light absorption layer described above comprises an organic polymer and colloidal quantum dots. Method for manufacturing a photodetector comprising an organic polymer-quantum dot composite light absorption layer.

12. In Paragraph 11, The step of forming the above quantum dot light absorption layer is, A step of synthesizing quantum dots using group IV-VI quantum dots; Step of preparing a ligand-substituted precursor solution; A step of dissolving the synthesized quantum dots in an organic solvent and then mixing them with the ligand-substituted precursor solution to improve the conductivity of the quantum dots; and A step of reacting the above-mentioned reacted quantum dots with a fluorine-based organic polymer; comprising Method for manufacturing a photodetector comprising an organic polymer-quantum dot composite light absorption layer.

13. In Paragraph 11, The above photodetector is the photodetector of claim 1, Method for manufacturing a photodetector comprising an organic polymer-quantum dot composite light absorption layer.

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