KR20220129806A - Optical sensor including quantum dots - Google Patents

Abstract

The present invention relates to an optical sensor including quantum dots having a core-shell structure. The optical sensor of the present invention comprises: a quantum dot layer including a plurality of quantum dots having a core shell structure with a specific component. Since the quantum dot layer includes a PN composite bonding structure which is provided between a first semiconductor layer and a second semiconductor layer, rather than a PN bonding structure to which the first semiconductor layer and the second semiconductor layer are directly bonded, the present invention reduces optical current by effectively protecting the quantum dot layer. By effectively generating reverse light current with high light emission and excellent energy absorption, and reducing current in an optical sensor due to the reverse light current when irradiating a light source to the optical sensor, the present invention suppresses an overcurrent state for increasing the entire current of the optical sensor. As a result, power consumption can be reduced by improving overall electrical characteristics.

Description

Optical sensor including quantum dots

The present invention relates to an optical sensor comprising quantum dots having a core-shell structure.

Silicon semiconductors commonly used in photosensors and image sensors have a problem in that quantum efficiency in the infrared band is significantly lower than that in the visible light band.

In addition, in the case of a conventional optical sensor, a PN junction is made using two different types of layers to increase the current when irradiating a light source, but in the case of this type of optical sensor, when the current increases by the light source, power consumption There was an increasing problem with this.

Republic of Korea Patent Publication No. 10-2018-0004994

The present invention is intended to solve the above problems, and the specific objects thereof are as follows.

The present invention includes a quantum dot layer including a plurality of quantum dots having a core-shell structure between the first semiconductor layer and the second semiconductor layer in the photodetecting layer disposed between the first electrode and the second electrode to generate a reverse photocurrent An object of the present invention is to provide a possible optical sensor.

The object of the present invention is not limited to the object mentioned above. The objects of the present invention will become more apparent from the following description, and will be realized by means and combinations thereof described in the claims.

An optical sensor according to the present invention includes a first electrode; a photodetector layer disposed on one surface of the first electrode; and a second electrode disposed on the photo-detecting layer, wherein the photo-detecting layer includes a quantum dot layer including a plurality of quantum dots having a core-shell structure.

The core of the quantum dot may include at least one selected from the group consisting of CdSe, CdTe, CdS, InP, ZnCdSe, PbS, PbSe, CGS, CIGS, and CIS.

The shell of the quantum dot may include at least one selected from the group consisting of ZnS, CdS, and ZnSe.

The photodetection layer may include a first semiconductor layer disposed between the quantum dot layer and the first electrode; and a second semiconductor layer disposed between the quantum dot layer and the second electrode.

The first semiconductor layer or the second semiconductor layer each independently has a band gap.

and may include at least one selected from the group consisting of a two-dimensional semiconductor material having a two-dimensional crystal structure, a semiconductor material containing silicon, a compound semiconductor material, and an organic semiconductor material.

The two-dimensional semiconductor material may include a transition metal dichalcogenide.

The transition metal includes at least one of molybdenum (Mo), tungsten (W), tin (Sn), niobium (Nb), tantalum (Ta), hafnium (Hf), titanium (Ti), and rhenium (Re), and ; And The chalcogen element may include at least one of sulfur (S), selenium (Se), and tellurium (Te).

The first semiconductor layer may be doped with a first conductivity type, and the second semiconductor layer may be doped with a second conductivity type electrically opposite to the first conductivity type.

The thickness of the first semiconductor layer or the second semiconductor layer may each independently have a range of 5 nm to 30 nm.

The first electrode or the second electrode may each independently include one or more selected from the group consisting of metal, graphene, transparent conductive oxide, and transparent conductive nitride.

The second electrode may be a transparent electrode having transmittance to light of a wavelength band to be detected.

It may further include a substrate disposed on the other surface of the first electrode.

The photosensor according to the present invention includes a quantum dot layer including a plurality of quantum dots having a core-shell structure between the first semiconductor layer and the second semiconductor layer, thereby effectively protecting the quantum dot layer and generating a reverse photocurrent Therefore, when the light source is irradiated to the photosensor, the current in the photosensor is reduced due to the reverse photocurrent and suppresses the overcurrent state in which the total current of the photosensor is increased. .

The effects of the present invention are not limited to the above-mentioned effects. It should be understood that the effects of the present invention include all effects that can be inferred from the following description.

1 is a cross-sectional view of an optical sensor according to the present invention.
2 is a flowchart schematically illustrating a method for manufacturing an optical sensor according to the present invention.
3 is a graph showing the result of emission intensity with respect to the wavelength of the quantum dot having a core-shell structure according to the present invention.
4A to 4C are graphs of current (A) according to time (seconds) per reaction wavelength (400 nm, FIG. 4A; 500 nm, FIG. 4B; 600 nm, FIG. 4C) in the photosensor according to the comparative example.
5A to 5C are graphs of current (A) according to time (seconds) per reaction wavelength (400 nm, FIG. 5A; 500 nm, FIG. 5B; 600 nm, FIG. 5C) in the photosensor according to the embodiment.

The above objects, other objects, features and advantages of the present invention will be easily understood through the following preferred embodiments in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided so that the disclosed subject matter may be thorough and complete, and that the spirit of the present invention may be sufficiently conveyed to those skilled in the art.

In describing each figure, like reference numerals have been used for like elements. In the accompanying drawings, the dimensions of the structures are enlarged than the actual size for clarity of the present invention. Terms such as first, second, etc. may be used to describe various elements, but the elements should not be limited by the terms. The above terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, a first component may be referred to as a second component, and similarly, a second component may also be referred to as a first component. The singular expression includes the plural expression unless the context clearly dictates otherwise.

In the present specification, terms such as “comprise” or “have” are intended to designate that a feature, number, step, operation, component, part, or combination thereof described in the specification exists, but one or more other features It is to be understood that it does not preclude the possibility of the presence or addition of numbers, steps, operations, components, parts, or combinations thereof. Also, when a part of a layer, film, region, plate, etc. is said to be “on” another part, this includes not only cases where it is “directly on” another part, but also cases where another part is in between. Conversely, when a part, such as a layer, film, region, plate, etc., is "under" another part, this includes not only cases where it is "directly under" another part, but also cases where there is another part in between.

Unless otherwise specified, all numbers, values, and/or expressions expressing quantities of ingredients, reaction conditions, polymer compositions and formulations used herein include, among other things, the numbers, values and/or expressions such that these numbers essentially occur in obtaining such values, among others. Since they are approximations reflecting various uncertainties in the measurement, it should be understood as being modified by the term "about" in all cases. Also, where the disclosure discloses numerical ranges, such ranges are continuous and inclusive of all values from the minimum to the maximum inclusive of the range, unless otherwise indicated. Furthermore, when such ranges refer to integers, all integers inclusive from the minimum to the maximum inclusive are included, unless otherwise indicated.

In this specification, when a range is described for a variable, the variable will be understood to include all values within the stated range including the stated endpoints of the range. For example, a range of “5 to 10” includes the values of 5, 6, 7, 8, 9, and 10, as well as any subranges such as 6 to 10, 7 to 10, 6 to 9, 7 to 9, etc. It will be understood to include any value between integers that are appropriate for the scope of the recited range, such as 5.5, 6.5, 7.5, 5.5 to 8.5 and 6.5 to 9, and the like. Also for example, a range of “10% to 30%” includes values such as 10%, 11%, 12%, 13%, and all integers up to and including 30%, as well as 10% to 15%, 12% to It will be understood to include any subrange, such as 18%, 20% to 30%, etc., as well as any value between reasonable integers within the scope of the recited range, such as 10.5%, 15.5%, 25.5%, and the like.

The conventional photosensor uses a method in which a PN junction is made using two different types of layers and a current increases when irradiating a light source, and there is a problem in that power consumption is increased when the current is increased by the light source.

Accordingly, the present inventors have intensively studied to solve the above problem, and as a result, a quantum dot layer having a core-shell structure between the first semiconductor layer and the second semiconductor layer in the photodetecting layer disposed between the first electrode and the second electrode In the case of manufacturing an optical sensor capable of generating a reverse photocurrent by including It was discovered that the power consumption was reduced by improving the characteristics, and the present invention was completed.

1 is a cross-sectional view of an optical sensor according to the present invention. Referring to this, the photosensor 1 includes a first electrode 10; a photodetector layer 20 disposed on one surface of the first electrode; and a second electrode 30 disposed on the photodetecting layer.

Preferably, it may further include a substrate 40 disposed on the other surface of the first electrode, the photo-detecting layer 20, specifically, a quantum dot layer 21; a first semiconductor layer 22 disposed between the quantum dot layer and the first electrode; and a second semiconductor layer 23 disposed between the quantum dot layer and the second electrode.

The first electrode 10 and the second electrode 30 serve to flow a current through the device, and the first electrode 10 includes metal, graphene, a transparent conductive oxide, and a transparent conductive nitride. It may include one or more selected from the group consisting of. Specifically, the metal may include at least one selected from the group consisting of Au, Ag, Al, and Cu, and the transparent conductive oxide may include ITO. On the other hand, the second electrode 20 should be made of a transparent electrode, and specifically, may include at least one selected from the group consisting of metal, graphene, transparent conductive oxide, and transparent conductive nitride. Specifically, the metal may include at least one selected from the group consisting of Au, Ag, Al, and Cu, and the transparent conductive oxide may include ITO.

Preferably, the first electrode may include graphene having high conductivity while being a two-dimensional material. In addition, since the second electrode is disposed in a direction in which light is incident, it may include single-layer graphene, which is a transparent electrode having transmittance to light of a wavelength band to be detected.

The photodetector layer 20 is a layer capable of generating a photocurrent by absorbing an external light source, and preferably, may generate a photocurrent by absorbing an external light source through the quantum dot layer 21 including a plurality of quantum dots.

Preferably, the quantum dots included in a plurality in the quantum dot layer are not particularly limited as long as they have a core-shell structure that is disposed between the first semiconductor layer and the second semiconductor layer to cause a reverse photocurrent phenomenon.

Specifically, the core of the quantum dot may include at least one selected from the group consisting of CdSe, CdTe, CdS, InP, ZnCdSe, PbS, PbSe, CGS, CIGS and CIS, and preferably CdSe absorbing the visible light region. may include.

In addition, the shell of the quantum dot may include at least one selected from the group consisting of ZnS, CdS and ZnSe, and preferably ZnS used to control the absorption wavelength region of CdSe.

The thickness of the shell of the quantum dot is preferably 0.2 nm to 1 nm. Out of the above range, if the thickness of the shell is too thin, the role of the shell is lost, and if the thickness of the shell is too thick, electrons do not enter the core.

Preferably, the quantum dots included in a plurality in the quantum dot layer may include CdSe in the core and ZnS in the shell so as to have high light emission and excellent energy absorption to cause an excellent reverse photocurrent phenomenon.

Quantum dots included in a plurality in the quantum dot layer have a core-shell structure having the above components, so that the absorption wavelength region can be controlled. In addition, since the first semiconductor layer and the second semiconductor layer doped with different conductivity types are disposed on both sides of the quantum dot layer having the above characteristics, the quantum dot layer is effectively protected and a reverse photocurrent can be generated, so that the light source is irradiated to the photosensor In this case, the current in the photosensor is reduced due to the reverse photocurrent, suppressing the overcurrent state in which the total current of the photosensor is increased, and consequently, overall electrical characteristics are improved and power consumption can be reduced.

The first semiconductor layer 22 and the second semiconductor layer 23 are positioned at the interface between the first electrode or the second electrode and the quantum dot layer, respectively, and serve to control the flow of current.

As a material used for the first semiconductor layer 22 and the second semiconductor layer 23 , any semiconductor material capable of performing the above function may be used. For example, it may include at least one selected from the group consisting of a two-dimensional semiconductor material having a band gap and a two-dimensional crystal structure, a semiconductor material including silicon, a compound semiconductor material, and an organic semiconductor material. Preferably, since the quantum dot layer has quantum dots of a two-dimensional structure, the use of a two-dimensional semiconductor material may be advantageous for the alignment of quantum dots having a plurality of core-shell structures of the quantum dot layer. For example, as a two-dimensional semiconductor material, transition metal dichalcogenide (TMD), which is a compound of a transition metal and a chalcogen element, h-BN (hexagonal BN), phosphorene, TiO _x , NbO _x , MnO _x , VaO _x , MnO ₃ , TaO ₃ , WO ₃ , MoCl ₂ , CrCl ₃ , RuCl ₃ , BiI ₃ , PbCl ₄ , GeS, GaS, GeSe, GaSe, PtSe ₂ , In ₂ Se ₃ , GaTe, InS , InSe, InTe, and the like. In this case, h-BN is formed in a hexagonal crystal structure by combining boron (B) and nitrogen (N). Phosphorine is a two-dimensional allotrope of black phosphorus. Preferably, it may include transition metal dichalcogenide (TMD), which is a two-dimensional semiconductor material having a band gap. The transition metal is, for example, among molybdenum (Mo), tungsten (W), tin (Sn), niobium (Nb), tantalum (Ta), hafnium (Hf), titanium (Ti), and rhenium (Re). It includes at least one, and the chalcogen element may include, for example, at least one of sulfur (S), selenium (Se), and tellurium (Te). For example, the transition metal dichalcogenide is MoS ₂ , WS ₂ , TaS ₂ , HfS ₂ , ReS ₂ , TiS ₂ , NbS ₂ , SnS ₂ , MoSe ₂ , WSe ₂ , TaSe ₂ , HfSe ₂ , ReSe ₂ , TiSe ₂ , NbSe ₂ , SnSe ₂ , MoTe ₂ , WTe ₂ , TaTe ₂ , HfTe ₂ , ReTe ₂ , TiTe ₂ , NbTe ₂ , SnTe ₂ .

The first semiconductor layer may be doped with a first conductivity type, and the second semiconductor layer may be doped with a second conductivity type electrically opposite to the first further type. For example, when the first electrode is a cathode and the second electrode is an anode, the first semiconductor layer may be doped n-type and preferably doped with MoS ₂ , and the second semiconductor layer is doped p-type It may be preferably doped with WSe ₂ . Conversely, when the first electrode is an anode and the second electrode is a cathode, the first semiconductor layer may be doped p-type and preferably doped with WSe ₂ , and the second semiconductor layer will be doped n-type. It may be preferably doped with WSe ₂ .

The thickness of the first semiconductor layer or the second semiconductor layer may each independently have a range of 5 nm to 30 nm, and preferably, a range of 10 nm to 20 nm. Out of the above range, if the thickness of the first semiconductor layer or the second semiconductor layer is too thin, there is a disadvantage of being vulnerable to defects, and if it is too thick, there is a disadvantage of excessive increase of the resistive component and loss of the function as a two-dimensional material. By using the first semiconductor layer or the second semiconductor layer having a thickness range that satisfies the range, there is an advantage in that electric charges on the photodetector layer recombine to reduce photocurrent.

That is, the photodetection layer included in the photosensor according to the present invention is not a PN junction structure in which the first semiconductor layer and the second semiconductor layer are directly coupled, but a plurality of quantum dots having a core-shell structure therebetween. Since it has a characteristic of having a PN composite junction structure including a quantum dot layer, it not only reduces the photocurrent by effectively protecting the quantum dot layer, but also has high light emission and excellent energy absorption, so it can effectively generate a reverse photocurrent, When irradiating the photosensor, the current in the photosensor is reduced due to the reverse photocurrent, suppressing the overcurrent state in which the total current of the photosensor is increased. As a result, the overall electrical characteristics are improved and power consumption can be reduced.

In addition, the present invention may further include a substrate disposed on the other surface of the first electrode. The substrate may include one or more selected from the group consisting of a conventional substrate that can be used in an optical sensor, for example, silicon, silicon oxide, glass, and a PET film as one that can be conventionally used in electrical devices, and , but is not limited to including only specific ingredients.

According to an embodiment of the present invention, the light source incident on the optical sensor satisfying the above characteristics is absorbed in the semiconductor layer to form an electron-hole pair, and a current signal generated by the electron-hole pair is transmitted to the readout circuit. can be output as a voltage signal. The photosensor according to an embodiment of the present invention is a photoelectric conversion device that converts light into an electrical signal, and may be used as a p-i-n type diode.

2 is a flowchart schematically illustrating a method for manufacturing an optical sensor according to the present invention. Referring to this, forming a first electrode on a substrate (S10), forming a photo-detecting layer on the first electrode (S20), forming a second electrode on the photo-detecting layer (S30) includes

In order to describe the method of manufacturing the optical sensor, content overlapping with the previous content may be omitted.

The forming of the first electrode ( S10 ) may be formed by transferring the first electrode prepared in advance by a CVD method on a previously prepared substrate.

Specifically, the step of forming the photodetecting layer (S20) includes the step of transferring the first semiconductor layer to the first electrode (S21), and a plurality of quantum dots having a core-shell structure on the first semiconductor layer. It may further include forming a quantum dot layer (S22), and transferring a second semiconductor layer on the quantum dot layer (S23).

The step (S21) of transferring the first semiconductor layer may include, specifically, preparing a metal layer, applying a semiconductor material on the metal layer to form a first semiconductor layer, and a polymer layer on the first semiconductor layer. It may include the steps of manufacturing a laminate by forming a laminate, removing the metal layer from the laminate, transferring the laminate from which the metal layer is removed to the first electrode, and removing the polymer layer.

The metal layer is not particularly limited as long as it is a material that can be etched later as a metal layer to which the semiconductor material can be applied. For example, a copper plate or an iron plate may be used, and a metal foil containing copper or iron may be used, and a substrate having excellent solubility in water such as NaCl may also be used.

A first semiconductor layer may be formed by coating a semiconductor material on the prepared metal layer by chemical vapor deposition (CVD). In the case of the conventional scotch tape method for manufacturing a semiconductor layer having a physically two-dimensional structure, there is a disadvantage in that mass production is impossible by directly peeling each layer using a scotch tape. On the other hand, chemical vapor deposition (CVD) is a method in which a precursor material is deposited in a gaseous state on a substrate to form a material layer having a two-dimensional structure. .

Specifically, the semiconductor material according to the present invention may be applied by chemical vapor deposition (CVD), preferably, a temperature of 950 to 1030° C., a pressure of 10 ^-3 mtorr to 760 torr, 5 min. The semiconductor material can be applied through CVD under the condition of 1 hr. Outside the above range, it is difficult to uniformly grow graphene in an atmosphere where the pressure is too low, and it tends to grow thick in an atmosphere where the pressure is too high. In addition, if the temperature is too low, there is a disadvantage of poor crystallinity, and if the temperature is too high, there is a disadvantage that the grown graphene is unstable at a high temperature and is etched.

The manufacturing of the laminate forming the polymer layer is a step of manufacturing the laminate by forming the polymer layer on the formed first semiconductor layer. The polymer layer serves to later transfer the first semiconductor layer in the stack to the first electrode while maintaining its shape. The polymer layer may include, for example, poly (methyl methacrylate) (PMMA).

The metal layer may be removed by etching or the like, and the laminate from which the metal layer is removed may be transferred such that the first semiconductor layer contacts the first electrode. Then, the polymer layer located on the upper part of the laminate may be removed by washing using acetone, an organic solvent, so that the quantum dot layer may be directly formed on the first semiconductor layer.

The forming of the quantum dot layer on the first semiconductor layer ( S22 ) is a step of forming a quantum dot layer including a plurality of quantum dots having the core-shell structure on the first semiconductor layer.

The quantum dot layer may be formed by stacking a plurality of quantum dots on the first semiconductor layer by a spin coating method.

The step of transferring the second semiconductor layer ( S23 ) is a step of transferring the second semiconductor layer on the quantum dot layer, and the specific steps may be the same as the step of transferring the first semiconductor layer ( S21 ).

Through the above steps, a photodetecting layer may be finally formed on the first electrode.

The step of forming the second electrode on the photo-detecting layer (S30) is a step of forming a second electrode on the second semiconductor layer on the photo-detecting layer, and the forming method includes: forming a first electrode; may be the same.

The present invention will be described in more detail with reference to the following examples. The following examples are only examples to help the understanding of the present invention, and the scope of the present invention is not limited thereto.

Example: Optical sensor manufacturing

(S10) The step of forming the first electrode on the substrate is as follows.

이하로 내려갈 때까지 H₂ 기체 15sccm을 3차로 공급하며 냉각시켰다. 그 다음, 상기 제1 반도체층 상에 PMMA를 포함하는 고분자층을 스핀코팅방법으로 형성시켜 적층체를 제조하였다. 그 다음, 상기 적층체에서 구리 포일(Cu foil)인 금속층을 식각방법으로 제거하였다. 그 다음, 상기 구리 포일(Cu foil)인 금속층이 제거된 적층체를 SiO2/Si 기판의 SiO₂에 그래핀이 맞닿게 전사시킬 수 있다. 그 다음, PMMA를 포함하는 고분자층을 아세톤을 이용하여 제거할 수 있다. 이에, 최종적으로, SiO₂/Si 기판인 기재 상에 그래핀이 형성되어 있는 제1 전극을 제조하였다. Specifically, the metal layer was prepared by first washing the copper foil (Cu foil) in the order of acetone (Acetone), isopropyl alcohol (Isopropylalcohol, IPA), and ethanol (Ethanol). After loading the substrate into a 2-inch quartz tube, Cu 35 nm as a catalyst and methane (CH4) as a precursor, H ₂ gas was supplied at 100 sccm, and annealing was performed for 90 minutes. Next, 100 sccm of H ₂ gas and 5 sccm of CH ₄ gas are first supplied for 1 minute, and then 100 sccm of H ₂ gas and 13 sccm of CH ₄ gas are supplied secondarily for 8 minutes to grow a functional layer containing graphene. After 8 minutes, the quartz tube is opened and the temperature of the substrate is 200

It was cooled by supplying 15 sccm of H ₂ gas three times until it went down below. Then, a polymer layer containing PMMA was formed on the first semiconductor layer by a spin coating method to prepare a laminate. Then, the metal layer, which is a copper foil, was removed from the laminate by an etching method. Thereafter, the laminate from which the metal layer, which is the copper foil, is removed, may be transferred so that the graphene contacts the SiO ₂ of the SiO 2 /Si substrate. Then, the polymer layer containing PMMA may be removed using acetone. Accordingly, finally, a first electrode in which graphene is formed on a substrate that is a SiO ₂ /Si substrate was prepared.

(S20) The step of forming the photodetecting layer is as follows.

Specifically, in the step of transferring the first semiconductor layer to the first electrode (S21), the copper foil is first washed with acetone, isopropylalcohol (IPA), and ethanol (Ethanol) in this order. A metal layer was prepared. Then, the semiconductor material was prepared through the following steps. Specifically, high-purity MoO ₃ (99.5%) and sulfur powder (99.5%) were placed in a quartz boat and placed in a chamber, and then argon (Ar) was injected in an amount of 150 sccm at 650 ° C for 30 minutes at normal pressure. Then, by cooling to room temperature, MoS ₂ as a semiconductor material was prepared. Then, by chemical vapor deposition (CVD), the semiconductor material, MoS ₂ , was applied to a metal layer that was a copper foil to form a first semiconductor layer. Then, a polymer layer containing PMMA was formed on the first semiconductor layer by a spin coating method to prepare a laminate. Then, the metal layer, which is a copper foil, was removed from the laminate by an etching method. Next, the first semiconductor layer may be transferred onto the first electrode formed in step S10 so as to contact the first electrode in the laminate from which the metal layer, which is the copper foil, is removed. Then, the polymer layer containing PMMA may be removed using acetone.

에서 700rpm으로 교반하여 혼합물을 제조하였다. 이와 별개로, Se 분말을 순도97%의 Trioctylphosphine(TOP)에 녹여 Se-TOP 착화물 용액을 제조한다. 상기 교반한 300

의 혼합물에 Se-TOP 착화물 용액을 빠른 속도로 주입하여 반응시킨다. 반응 중에서는 질소 분위기에서 일정한 교반속도를 유지하였다. 상기의 방법으로 CdSe 코어를 제조하였다. 그 다음, 추가적으로 ZnMe₂와(TMS)₂S를 주입하여 CdSe 코어와 ZnS 쉘을 갖는 양자점을 제조한다. 그 다음, 상기 양자점 나노 입자를 헥산(hexane) 15mL에 녹여 정제한다. CHCl₃와 CH₃OH를 1:1의 부피비로 혼합한 용액 15mL를 나노 입자가 녹아 있는 헥산(hexane) 용액에 첨가 하여 양자점을 추출하였다. 혼합 용액의 상층에는 순수한 양자점 나노 입자가 녹아 있기 때문에 상층만 분리하였다. 분리된 상층 용액에 아세톤(acetone)을 사용하여 원심분리 시킨다. 형성되는 양자점을 240

에서 30분간 반응시켜 최종적으로 양자점 나노 입자를 얻었다. 상기 얻은 양자점 나노 입자는 스핀코팅 방법을 통해 제1 반도체층 상에 형성시켰다.The step (S22) of forming a quantum dot layer including a plurality of quantum dots having a core-shell structure on the first semiconductor layer is as follows. First, trioctylamine (TOA), oleic acid (OA), and cadmium oxide were placed in a 125ml flask equipped with a reflux condenser, and 300

A mixture was prepared by stirring at 700 rpm. Separately, a Se-TOP complex solution is prepared by dissolving Se powder in trioctylphosphine (TOP) having a purity of 97%. the stirred 300

A solution of the Se-TOP complex is injected into the mixture at a high rate to react. During the reaction, a constant stirring speed was maintained in a nitrogen atmosphere. A CdSe core was prepared by the above method. Then, ZnMe ₂ and (TMS) ₂ S are additionally implanted to prepare quantum dots having a CdSe core and a ZnS shell. Then, the quantum dot nanoparticles are dissolved in 15 mL of hexane and purified. Quantum dots were extracted by adding 15 mL of a solution in which CHCl ₃ and CH ₃ OH were mixed in a volume ratio of 1:1 to a hexane solution in which nanoparticles were dissolved. Since pure quantum dot nanoparticles were dissolved in the upper layer of the mixed solution, only the upper layer was separated. The separated supernatant solution is centrifuged using acetone. 240 quantum dots to form

Finally, quantum dot nanoparticles were obtained by reacting for 30 minutes. The obtained quantum dot nanoparticles were formed on the first semiconductor layer through a spin coating method.

에서 반응시켰다. 그 후, Carrier gas인 아르곤 80sccm, 수소 20sccm를 압력은 1Torr로 유지시키면서 투입 시키면서, 925

에서 15분간 반응시킨 뒤 상온으로 냉각하여 최종적으로 반도체 물질인 WSe2 기능층을 형성한다.In the step (S23) of transferring the second semiconductor layer on the quantum dot layer, the second semiconductor layer is transferred onto the quantum dot layer rather than the first electrode layer by preparing WSe ₂ rather than MoS ₂ as a semiconductor material. It can be transcribed in the same way as Specifically, a method for preparing WSe ₂ from a semiconductor material is as follows. A metal layer, which is a copper foil, was placed in the chamber, and 0.3 g of WO ₃ and Se powder were placed in a ceramic boat divided into two compartments, respectively, 270

reacted in After that, while the carrier gas, argon 80sccm and hydrogen 20sccm, was introduced while maintaining the pressure at 1 Torr, 925

After reacting for 15 minutes at room temperature, it is cooled to room temperature to finally form a WSe2 functional layer, which is a semiconductor material.

(S30) The step of forming the second electrode on the photodetecting layer is as follows.

Specifically, the second electrode is a transparent electrode having transmittance to light of a wavelength band to be detected, and was formed by transferring single-layer graphene, which is a pre-prepared transparent electrode, like the first electrode.

Comparative Example: Optical sensor manufacturing

Compared with the example,

A photosensor was manufactured in the same manner as in Example, except that the photodetector layer did not include a quantum dot layer including a plurality of quantum dots having a core-shell structure.

Experimental Example 1: Characteristics of quantum dots having a core-shell structure

The quantum dots having a core-shell structure prepared in Examples were irradiated with 532 nm laser light to measure photoluminescence, and the results are shown in FIG. 3 .

Specifically, FIG. 3 is a graph showing the result of photoluminecence with respect to the wavelength of the quantum dot having a core-shell structure according to the present invention.

Referring to FIG. 3 , it can be seen that light is emitted at 610 nm. That is, the quantum dot having a core-shell structure according to the present invention has a light emission characteristic at 610 nm.

Experimental Example 2: Checking the presence of reverse photocurrent of the optical sensor

After the photosensors were manufactured according to Examples and Comparative Examples, currents according to time for each reaction wavelength were checked, and the results are shown in FIGS. 4A to 4C and 5A to 5C.

Specifically, FIGS. 4A to 4C are current (A) graphs according to time (seconds) per reaction wavelength (400 nm, FIG. 4A; 500 nm, FIG. 4B; 600 nm, FIG. 4C) in the photosensor according to the comparative example. 5A to 5C are graphs of current (A) according to time (seconds) per reaction wavelength (400 nm, FIG. 5A; 500 nm, FIG. 5B; 600 nm, FIG. 5C) in the photosensor according to the embodiment.

Referring to FIGS. 4A to 4C , when the light source for each reaction wavelength is irradiated, a general photocurrent flows and it can be seen that the current increases as time passes.

On the other hand, referring to FIGS. 5A to 5C , when the light source for each reaction wavelength is irradiated, in the light source for the reaction wavelength that the quantum dot having a core-shell structure in the quantum dot layer can absorb, the reverse photocurrent flows even over time. was found to decrease.

That is, the photosensor of the present invention includes a quantum dot layer including a plurality of quantum dots having a core-shell structure having a specific component, and the quantum dot layer is a PN in which the first semiconductor layer and the second semiconductor layer are directly coupled. Because it has the characteristic of having a PN composite junction structure included in between, rather than a junction structure, it not only reduces photocurrent by effectively protecting the quantum dot layer, but also has high light emission and excellent energy absorption to effectively generate reverse photocurrent. Therefore, when the light source is irradiated to the photosensor, the current in the photosensor is reduced due to the reverse photocurrent, thereby suppressing the overcurrent state in which the total current of the photosensor is increased. have.

1: light sensor
10: first electrode layer, 20: photodetecting layer, 30: second electrode layer, 40: substrate
21: first semiconductor layer, 22: quantum dot layer 23: second semiconductor layer

Claims (12)

a first electrode;
a photodetector layer disposed on one surface of the first electrode; and
a second electrode disposed on the photo-detecting layer;
The photodetector layer comprises a quantum dot layer comprising a plurality of quantum dots having a core-shell structure. According to claim 1,
The quantum dot core includes at least one selected from the group consisting of CdSe, CdTe, CdS, InP, ZnCdSe, PbS, PbSe, CGS, CIGS and CIS. The method of claim 1,
The quantum dot shell includes at least one selected from the group consisting of ZnS, CdS and ZnSe. According to claim 1,
The photodetector layer is
a first semiconductor layer disposed between the quantum dot layer and the first electrode; and
The photosensor further comprising a; a second semiconductor layer disposed between the quantum dot layer and the second electrode. 5. The method of claim 4,
The first semiconductor layer or the second semiconductor layer each independently has a band gap.
and a two-dimensional semiconductor material having a two-dimensional crystal structure, a semiconductor material containing silicon, a compound semiconductor material, and at least one selected from the group consisting of an organic semiconductor material. 6. The method of claim 5,
The two-dimensional semiconductor material is an optical sensor comprising a transition metal dichalcogenide. 7. The method of claim 6,
The transition metal includes at least one of molybdenum (Mo), tungsten (W), tin (Sn), niobium (Nb), tantalum (Ta), hafnium (Hf), titanium (Ti), and rhenium (Re), and ; and
The chalcogen element is a photosensor comprising at least one of sulfur (S), selenium (Se), and tellurium (Te). 6. The method of claim 5,
wherein the first semiconductor layer is doped with a first conductivity type, and the second semiconductor layer is doped with a second conductivity type electrically opposite to the first conductivity type. According to claim 1,
The thickness of the first semiconductor layer or the second semiconductor layer is each independently in the range of 5nm to 30nm optical sensor. According to claim 1,
The first electrode or the second electrode may each independently include at least one selected from the group consisting of metal, graphene, transparent conductive oxide, and transparent conductive nitride. According to claim 1,
The second electrode is a transparent electrode having a transmittance for light of a wavelength band to be detected. According to claim 1,
The photosensor further comprising a substrate disposed on the other surface of the first electrode.

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