Infrared photodiode comprising surface-modified electron transport layer and manufacturing method thereof

Abstract

The photodiode comprising a surface-modified electron transport layer proposed in an embodiment of the present invention has a structure comprising a metal electrode, a hole transport layer, a light absorbing layer, an electron transport layer, and a transparent electrode, and comprises a sulfur-modified layer on the surface of the electron transport layer that is adjacent to the light absorbing layer.

Description

Infrared photodiode including a surface-modified electron transport layer and method for manufacturing the same

[0001] The present invention relates to a photodiode and a method for manufacturing the same, and more specifically, to a photodetector including an electron transport layer and a method for manufacturing the same.

[0002]

[0003] With the advent of the Fourth Industrial Revolution, the importance of non-radio frequency bands, particularly the near-infrared band, is gradually being highlighted. Due to wavelength characteristics such as low atmospheric scattering and high visual stability, the near-infrared band is being utilized in various application fields such as infrared imaging, remote sensing, autonomous driving, and medical imaging technology.

[0004] Research on photodiode devices capable of exhibiting high efficiency in the infrared band is essential for the development of these applications. In particular, colloidal quantum dots are attracting attention due to their advantages, such as the ability to adjust the bandgap based on quantum confinement effects and tune electrical properties through various surface ligand substitution techniques. Unlike materials requiring conventional high-temperature vacuum deposition processes, colloidal quantum dot-based photodiodes can be fabricated via solution processing at room temperature, offering the strength of lower production costs and the potential for mass production.

[0005] Meanwhile, one of the key factors determining the efficiency of such photodiodes is the performance of the electron transport layer. The electron transport layer plays a role in efficiently transporting electrons within the photodiode, and it is generally known that metal oxides such as zinc oxide (ZnO), titanium oxide (TiO2), and tin oxide (SnO2) are primarily used. While these materials provide excellent electrical conductivity and light transmittance, fabrication via solution processes can lead to numerous surface defects that form trap states in the electron transport paths, thereby increasing the device's dark current and degrading efficiency.

[0006] To address this, various surface treatment technologies for electron transport layers have been studied. Previously, halogen-based treatments, such as chlorine, were used to suppress defects on the surface of electron transport layers, but this method had limitations in terms of long-term stability. Consequently, there was a need for new treatment technologies capable of more effectively suppressing surface defects in electron transport layers.

[0007]

[0008] The present invention is proposed to solve the aforementioned conventional problems and aims to improve the voltage stability and driving stability of the device by suppressing surface defects through modification of the surface of the electron transport layer, thereby reducing the dark current of the photodiode and minimizing trap states in the charge transfer path. Through this, the invention aims to realize a high-performance photodiode having high sensitivity and low noise characteristics in the infrared band.

[0009] In addition, embodiments of the present invention are intended to provide a high-efficiency photodiode capable of receiving light in a wide wavelength range from 900 nm to 1600 nm in the infrared band by adding a sulfur-based modified layer between the electron transport layer and the light absorption layer to reduce physical and chemical defects in the electron transport layer and maximize electron transport efficiency.

[0010] Furthermore, the present invention aims to implement a photodiode fabrication technology suitable for mass production and to lower production costs by introducing a room-temperature solution process-based fabrication method that can replace existing high-temperature heat treatment and high-cost manufacturing processes. Through this, the invention seeks to provide economical and highly reliable photodiodes that can be utilized in various application fields such as high-sensitivity infrared imaging, autonomous driving, LiDAR sensors, and medical imaging.

[0011] 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.

[0012]

[0013] A photodiode comprising a surface-modified electron transport layer according to one embodiment of the present invention may include a sulfur-modified layer on the surface of the electron transport layer adjacent to the light absorption layer, in a photodiode composed of a metal electrode, a hole transport layer, a light absorption layer, an electron transport layer, and a transparent electrode.

[0014] According to one embodiment of the present invention, the sulfur-modified layer may be coated with a thiol-based material.

[0015] According to one embodiment of the present invention, the sulfur-modified layer may include one or more of dithiol-based materials including 1,2-ethanedithiol (EDT), poly(ethylene glycol)dithiol (PEG dithiol), and 1,2-benzene-1,2-dithiol.

[0016] According to one embodiment of the present invention, the sulfur-modified layer may have a thickness of 20 nm to 50 nm.

[0017] According to one embodiment of the present invention, the light absorption layer is of type I or 10 15 (1 cm 3 It includes weak n-type or p-type quantum dots having a doping concentration within the number of doped atoms per unit volume, and can receive light in the infrared region of the wavelength range of 900 nm to 1600 nm.

[0018] According to one embodiment of the present invention, the light absorption layer comprises a quantum dot material, and the quantum dot material may comprise one or more of a Group 1 compound based on cadmium (Cd), lead (Pb), silver (Ag), or mercury (Hg) containing one of sulfur (S), selenium (Se), or tellurium (Te), or a Group 2 compound based on indium (In) containing one of phosphorus (P), arsenic (As), or antimony (Sb).

[0019] According to one embodiment of the present invention, the hole transport layer has a thickness of 20 nm to 100 nm and nickel oxide (NiO x ) and molybdenum oxides (MoO₂) x It may include a p-type quantum dot material substituted with a metal oxide or ligand containing )

[0020] According to one embodiment of the present invention, the electron transport layer has a thickness of 20 nm to 50 nm and may include one of a metal oxide including zinc oxide (ZnO), titanium oxide (TiO2) and tin oxide (SnO2).

[0021] According to one embodiment of the present invention, the metal electrode may be deposited with one or more metals selected from the group consisting of gold (Au), silver (Ag), aluminum (Al), platinum (Pt) and copper (Cu).

[0022] According to one embodiment of the present invention, the method may include the steps of preparing a lower electrode deposited on a glass substrate, forming an electron transport layer by coating on the lower electrode, forming a sulfur-modified layer on the upper surface of the electron transport layer, forming a light absorption layer on the sulfur-modified layer, forming a hole transport layer on the light absorption layer, and forming an upper electrode on the hole transport layer.

[0023] According to one embodiment of the present invention, the sulfur-modified layer may be formed by coating a thiol-based material on the upper surface of the electron transport layer.

[0024] According to one embodiment of the present invention, the photodiode may be a device comprising one or more of the components of a photodiode according to one embodiment of the present invention described above.

[0025]

[0026] According to one embodiment of the present invention, by modifying the surface of the electron transport layer with sulfur to suppress surface defects, the dark current of the photodiode is reduced and trap conditions in the charge transport path are minimized, thereby ensuring high voltage stability and driving stability.

[0027] In addition, according to one embodiment of the present invention, by introducing an electron transport layer modified with sulfur using a thiol-based material, the charge transfer efficiency within the photodiode is improved, and the interfacial coupling with the light absorption layer is improved, thereby providing high sensitivity and low noise characteristics in the infrared band.

[0028] In addition, according to one embodiment of the present invention, by proposing a technique for forming an electron transport layer and a sulfur-based modified layer through a solution process using ink at room temperature, it is possible to implement a photodiode fabrication technique that lowers production costs and enables mass production.

[0029] In addition, according to one embodiment of the present invention, by utilizing a quantum dot-based light absorption layer capable of efficiently absorbing light in the infrared band together with the electron transport layer, it is possible to provide a high-performance photodiode in the infrared region.

[0030] In addition, according to one embodiment of the present invention, a high-sensitivity photodiode having low dark current and high quantum efficiency can be realized by optimizing the thickness and material of each stacked structure of the hole transport layer, the light absorption layer, the electron transport layer, and the metal electrode.

[0031] 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.

[0032]

[0033] FIG. 1 is a figure illustrating a method for manufacturing a sulfur-modified layer on the surface of an electron transport layer according to one embodiment of the present invention.

[0034] Figure 2 is a graph showing a comparison of dark current characteristics between a photodiode (light line) including a sulfur-modified layer of the electron transport layer according to one embodiment of the present invention and a photodiode (dark line) that is identically manufactured except that it does not include a sulfur-modified layer as a comparative example (control group).

[0035] Figure 3 is a graph showing the dark current characteristics in a reverse bias state between a photodiode (light line) including a sulfur-modified layer of the electron transport layer according to one embodiment of the present invention and a photodiode (dark line) that is identical except that it does not include a sulfur-modified layer as a control.

[0036]

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042]

[0043] A photodiode comprising a surface-modified electron transport layer according to one embodiment of the present invention may include a sulfur-modified layer on the surface of the electron transport layer adjacent to the light absorption layer, in a photodiode composed of a metal electrode, a hole transport layer, a light absorption layer, an electron transport layer, and a transparent electrode.

[0044] The electron transport layer described above is a layer generally included in a photodiode that plays a role in efficiently transferring charge, and it is important to suppress trap states that may occur in the electron transport path. In the embodiments of the present invention, an attempt was made to reduce surface defects and increase charge transfer efficiency by adding a sulfur-based modification layer to the surface of the electron transport layer. In the embodiments described later, the sulfur-modified layer can be formed using 1,2-ethanedithiol (EDT), but it can be replaced with any other thiol-based material. In the embodiments described later, zinc oxide (ZnO) was used as the electron transport layer, but the zinc oxide can be replaced with any other metal oxides such as titanium oxide (TiO2), tin oxide (SnO2), or indium oxide (In2O3). Additionally, if necessary, materials such as graphene-doped materials or fluorine-doped oxides (FTO) can also be added to the electron transport layer according to the purpose, and the present invention does not particularly limit the components of the electron transport layer as long as the sulfur-modified layer is formed to achieve the aforementioned purpose.

[0045]

[0046] According to one embodiment of the present invention, the sulfur-modified layer may be coated with a thiol-based material.

[0047] Thiol-based materials play a key role in enhancing bonding strength and suppressing defects on the surface of electron transport layers. EDT (1,2-Ethanedithiol) is one of the thiol-based materials commonly used for this purpose and can be uniformly formed on the surface of an electron transport layer via a simple spin coating process.

[0048]

[0049] According to one embodiment of the present invention, the sulfur-modified layer may include one or more of dithiol-based materials including 1,2-ethanedithiol (EDT), poly(ethylene glycol)dithiol (PEG dithiol), and 1,2-benzene-1,2-dithiol.

[0050] These dithiol-based materials provide a unique passivation effect on the surface of the electron transport layer, reducing dark current and stabilizing charge transport pathways. Additionally, since these materials can be processed using low-temperature solution processes, they can reduce the fabrication cost of photodiodes. Dithiol-based materials are effective in reducing surface oxidation and charge trap states, and can increase electron transport efficiency.

[0051] In addition, various thiol-based materials can be used as substitutes or additions. All of these materials can optimize interfacial properties through chemical interactions with the electron transport layer material.

[0052]

[0053] According to one embodiment of the present invention, the sulfur-modified layer may have a thickness of 20 nm to 50 nm.

[0054] The thickness of the sulfur-modified layer can play an important role in balancing the electrical and optical properties of the device. If the thickness of the sulfur-modified layer is less than 20 nm, the surface passivation effect may not be sufficient, and if it exceeds 50 nm, a problem of increased resistance in the charge transfer path may occur. When manufactured according to the embodiments described below, the thickness of the modified layer can be adjusted as much as necessary depending on the spin coating speed, solution concentration, and process conditions. The thickness of the sulfur-modified layer may preferably be 25 nm to 45 nm. More preferably, the thickness of the sulfur-modified layer may be 30 nm or more and 40 nm or less.

[0055]

[0056] According to one embodiment of the present invention, the light absorption layer is of type I or 10 15 (1 cm 3 It includes weak n-type or p-type quantum dots having a doping concentration within the number of doped atoms per unit volume, and can receive light in the infrared region of the wavelength range of 900 nm to 1600 nm.

[0057] The quantum dots included in the light absorption layer may be colloidal quantum dots. The colloidal quantum dots are easy to control the band gap due to the quantum confinement effect, and can be realized as p-type, n-type, or i-type materials through surface ligand substitution and surface control technology.

[0058]

[0059] According to one embodiment of the present invention, the light absorption layer comprises a quantum dot material, and the quantum dot material may comprise one or more of a Group 1 compound based on cadmium (Cd), lead (Pb), silver (Ag), or mercury (Hg) containing one of sulfur (S), selenium (Se), or tellurium (Te), or a Group 2 compound based on indium (In) containing one of phosphorus (P), arsenic (As), or antimony (Sb).

[0060] Furthermore, unlike conventional single-infrared absorbing materials that require a high-temperature vacuum deposition process, the aforementioned quantum dots can be stacked to form optoelectronic devices via a room-temperature solution process. In this process, these quantum dots can exhibit high absorption characteristics in the infrared band by exerting a quantum confinement effect at specific sizes. When the doping concentration is determined to an appropriate level, conductivity characteristics can be adjusted while maintaining the intrinsic properties of the quantum dots.

[0061]

[0062] According to one embodiment of the present invention, the hole transport layer has a thickness of 20 nm to 100 nm and nickel oxide (NiO x ) and molybdenum oxides (MoO₂) x It may include a p-type quantum dot material substituted with a metal oxide or ligand containing )

[0063] The above hole transport layer can perform the role of efficiently moving holes to the upper electrode. The aforementioned nickel oxide (NiO x ) and molybdenum oxide (MoO x) can be selected as a material known to be excellent in terms of stability and efficiency. In addition, organic materials such as PEDOT:PSS may also be applied as additives or substitutes to the hole transport layer. Furthermore, quantum dots substituted with ligands (p-type PbS or PbSe) may also be applied as a hole transport layer material. As such, in the present invention, the hole transport layer is not specifically limited as long as the effect can be realized through the introduction of an electron transport layer including a sulfur-modified layer.

[0064]

[0065] According to one embodiment of the present invention, the electron transport layer has a thickness of 20 nm to 50 nm and may include one of a metal oxide including zinc oxide (ZnO), titanium oxide (TiO2) and tin oxide (SnO2).

[0066] The electron transport layer described above plays a role in efficiently transporting electrons in a photodiode device and can form a charge transfer path between the light absorption layer and the electrode. The metal oxide materials of the electron transport layer have excellent electrical properties and provide optical transparency, which can maximize device efficiency.

[0067] The thickness of the electron transport layer may be an important factor that significantly affects the electrical and optical characteristics of the device. The thickness of the electron transport layer may be between 20 nm and 50 nm. This range is suitable for optimizing electron transport efficiency without interfering with light absorption by the light absorption layer. More specifically, if the thickness of the electron transport layer is less than 0 nm, problems such as reduced charge transfer efficiency and increased leakage current may occur. If the thickness of the electron transport layer exceeds 50 nm, problems such as increased resistance in the electron transport path and reduced light transmittance may occur due to the increased thickness. The thickness of the electron transport layer may preferably be 25 nm or more. Additionally, the thickness of the electron transport layer may be 45 nm or less. More preferably, the thickness of the electron transport layer may be between 30 nm and 40 nm.

[0068]

[0069] According to one embodiment of the present invention, the metal electrode may be deposited with one or more metals selected from the group consisting of gold (Au), silver (Ag), aluminum (Al), platinum (Pt) and copper (Cu).

[0070] The metal electrode described above can perform electrical contact and charge collection of the device. Gold (Au) is chemically stable, and silver (Ag) is known as a material that provides high conductivity and cost-effectiveness. Aluminum (Al) has the advantages of being lightweight and low-cost, and platinum (Pt) and copper (Cu) can also be selected and used for specific purposes. As such, in the present invention, the type of the metal electrode is not specifically limited as long as it is a material that is typically applicable to the metal electrode of a photodiode.

[0071]

[0072] According to one embodiment of the present invention, the method may include the steps of preparing a lower electrode deposited on a glass substrate, forming an electron transport layer by coating on the lower electrode, forming a sulfur-modified layer on the upper surface of the electron transport layer, forming a light absorption layer on the sulfur-modified layer, forming a hole transport layer on the light absorption layer, and forming an upper electrode on the hole transport layer.

[0073] FIG. 1 is a figure illustrating a method for manufacturing a sulfur-modified layer on the surface of an electron transport layer according to one embodiment of the present invention.

[0074] Figure 1 illustrates the step-by-step process of forming a sulfur-based passivation layer by coating a zinc oxide (ZnO) electron transport layer on a transparent electrode (ITO) and then modifying the surface of the electron transport layer with sulfur by spin-coating EDT (1,2-Ethanedithiol), which is one of the thiol-based materials. In this way, in one embodiment of the present invention, a sulfur-modified layer can be formed on the upper surface of the electron transport layer using a spin-coating method.

[0075]

[0076] According to one embodiment of the present invention, the sulfur-modified layer may be formed by coating a thiol-based material on the upper surface of the electron transport layer.

[0077] According to one embodiment of the present invention, the photodiode may be a device comprising one or more of the components of a photodiode according to one embodiment of the present invention described above.

[0078]

[0079] <Example>

[0080] The following describes the effects of a photodiode comprising a sulfur-modified electron transport layer according to one embodiment of the present invention, which the inventors fabricated and tested through repeated experiments.

[0081]

[0082] The inventors fabricated a number of photodiode samples including a sulfur-modified electron transport layer within the scope of the embodiments described above and tested whether the embodiments described above operated as intended.

[0083] First, an electron transport layer was fabricated by spin-coating an electron transport layer material containing a metal oxide, such as zinc oxide, onto an indium-tin oxide (ITO) transparent electrode deposited on a glass substrate at 3000 rpm for 30 seconds. The electron transport layer was fabricated with an appropriately deformed thickness within 20 nm to 50 nm.

[0084] Subsequently, a sulfur-surfaced electron transport layer was fabricated by depositing an additional thiol layer on the electron transport layer. The sulfur-modified layer was fabricated by spin-coating at 1500 rpm for 8 seconds, with the thiol layer material including one or more of dithiol series materials such as 1,2-ethanedithiol (EDT), poly(ethylene glycol)dithiol (PEG dithiol), and 1,2-benzene-1,2-dithiol.

[0085] The solvent used for fabricating the thiol thin film included one or more of ethyl acetate, acetonitrile, and propionitrile, and the selected thiol material was diluted to a concentration of 0.01% to 0.1%. The thickness of the thiol thin film was fabricated by varying it within the range of 20 nm to 50 nm.

[0086] On top of that, an n-type or p-type quantum dot light absorption layer having an I-type or weak doping concentration was fabricated by spin-coating at 800 rpm for 10 seconds and at 2000 rpm for 20 seconds. According to the embodiment of the present invention described above, a hole transport layer was fabricated with a thickness of 20 nm to 100 nm.

[0087] Finally, an electrode was fabricated by thermally depositing a metal electrode using a material selected from gold (Au), silver (Ag), aluminum (Al), platinum (Pt), copper (Cu), and platinum (Pt) on top of it. According to the embodiment of the present invention described above, the metal electrode was fabricated to a thickness of 100 nm to 130 nm.

[0088] And the inventors prepared a comparative example sample under conditions and in a manner exactly identical to the method prepared above, except that it does not include a sulfur-modified layer.

[0089]

[0090] Figure 2 is a graph showing a comparison of dark current characteristics between a photodiode (light line) including a sulfur-modified layer of the electron transport layer according to one embodiment of the present invention and a photodiode (dark line) that is identically manufactured except that it does not include a sulfur-modified layer as a comparative example (control group).

[0091] In FIG. 2, when the surface of the electron transport layer is modified with sulfur, the dark current tends to decrease overall. This can be interpreted as a result of the sulfur-based modified layer (EDT coating) suppressing defects on the surface of the electron transport layer, thereby minimizing trap states that may occur in the charge transport path and improving electron transfer efficiency. In particular, the reduction in dark current near 0V indicates that the structure of the photodiode according to the embodiment of the present invention can contribute to enhancing device stability and low noise characteristics.

[0092] Figure 3 is a graph showing the dark current characteristics in a reverse bias state between a photodiode (light line) including a sulfur-modified layer of the electron transport layer according to one embodiment of the present invention and a photodiode (dark line) that is identical except that it does not include a sulfur-modified layer as a control.

[0093] The graph in Fig. 3 shows the dark current characteristics in a reverse bias state using the example of the present invention manufactured in Fig. 2 and the respective photodiodes fabricated as a comparative example (control group).

[0094] As can be seen in the graph of Figure 3, the photodiode corresponding to the embodiment of the present invention using an electron transport layer modified with sulfur tends to have a relatively lower overall dark current even in a reverse bias state. This means that the photodiode including the sulfur-modified layer introduced in the embodiment of the present invention suppresses defects on the surface of the electron transport layer, thereby reducing leakage current that may occur in the electron transport path, and improves the stability and electrical characteristics of the device even in a reverse bias state.

[0095] As shown in Figure 3, the difference between the two curves becomes more pronounced as the reverse bias voltage increases, which suggests that the sulfur-modified layer contributed to effectively maintaining the performance of the electron transport layer even under high voltage conditions. These results indicate that the introduction of a sulfur-modified layer on the surface played a significant role in ensuring low dark current characteristics and high driving stability of the photodiode.

[0096]

[0097] 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. In a photodiode composed of a metal electrode - hole transport layer - light absorption layer - electron transport layer - transparent electrode, A layer comprising a sulfur-modified layer on the surface of an electron transport layer adjacent to a light absorption layer, Photodiode comprising a surface-modified electron transport layer.

2. In Paragraph 1, The above sulfur-modified layer is coated with a thiol-based material, Photodiode comprising a surface-modified electron transport layer.

3. In Paragraph 1, The sulfur-modified layer comprises one or more of dithiol-based materials including 1,2-ethanedithiol (1,2-Ethanedithiol, EDT), poly(ethylene glycol)dithiol (PEG dithiol), and 1,2-benzenedithiol (Benzene-1,2-dithiol). Photodiode comprising a surface-modified electron transport layer.

4. In Paragraph 1, The sulfur-modified layer has a thickness of 20 nm to 50 nm. Photodiode comprising a surface-modified electron transport layer.

5. In Paragraph 1, The above light absorption layer is Type I or 10 15 It includes n-type or p-type quantum dots having a doping concentration within the range, Capable of receiving light in the infrared region of the wavelength range of 900 nm to 1600 nm, Photodiode comprising a surface-modified electron transport layer.

6. In Paragraph 1, The light absorption layer above includes a quantum dot material, and The above quantum dot material is, A compound comprising one or more of a Group 1 compound based on cadmium (Cd), lead (Pb), silver (Ag), or mercury (Hg) containing any one of sulfur (S), selenium (Se), or tellurium (Te), or a Group 2 compound based on indium (In) containing any one of phosphorus (P), arsenic (As), or antimony (Sb). Photodiode comprising a surface-modified electron transport layer.

7. In Paragraph 1, The hole transport layer has a thickness of 20 nm to 100 nm and comprises a metal oxide including nickel oxide and molybdenum oxide or a p-type quantum dot material substituted with a ligand. Photodiode comprising a surface-modified electron transport layer.

8. In Paragraph 1, The electron transport layer has a thickness of 20 nm to 50 nm and comprises one of a metal oxide including zinc oxide, titanium oxide, and tin oxide. Photodiode comprising a surface-modified electron transport layer.

9. In Paragraph 1, The metal electrode is one on which one or more selected from the group consisting of gold, silver, aluminum, platinum, and copper are deposited. Photodiode comprising a surface-modified electron transport layer.

10. A step of preparing a lower electrode deposited on a glass substrate; A step of forming an electron transport layer by coating it on the lower electrode; A step of forming a sulfur-modified layer on the upper surface of the electron transport layer; A step of forming a light absorption layer on the sulfur-modified layer above; A step of forming a hole transport layer on the light absorption layer; and The method includes the step of forming an upper electrode on the hole transport layer; The sulfur-modified layer is formed by coating a thiol-based material on the upper surface of the electron transport layer. Method for manufacturing a photodiode comprising a surface-modified electron transport layer.

11. In Paragraph 10, The above photodiode is the photodiode of claim 1, Method for manufacturing a photodiode comprising a surface-modified electron transport layer.

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