Background
Infrared light is a form of electromagnetic radiation that is ubiquitous in natural and artificial environments. And the infrared imaging technology has larger application potential in the emerging fields of intelligent sensing, machine vision, automatic driving and the like. However, infrared light is not directly perceived by the naked eye. Thus, infrared photodetectors have been invented to detect infrared light, and photoactive materials play a critical role in this process, with semiconductor materials being commonly used. Commercial infrared photodetectors are typically fabricated from conventional narrow bandgap bulk inorganic semiconductors (e.g., inSb, ge, hgCdTe, inGaAs). Bulk semiconductor materials, however, are quite limited. First, they are typically grown under extreme temperature and vacuum conditions, which are costly. Second, the epitaxial growth that is commonly employed is on lattice-matched crystalline substrates, which makes this type of infrared photodetectors expensive, inflexible, and limited. Therefore, there is an urgent need for infrared detector replacement materials that are small in size, dark current, and power consumption.
Compared with the traditional bulk semiconductor, the infrared quantum dot has the advantages of easy processing, good flexibility, good light stability, high absorption coefficient and the like, and the colloid photoelectric detector has the advantages of being adjustable in corresponding wave band, excellent in detection performance, low in price, compatible in process and the like, and has great potential for replacing a silicon-based pixel array and realizing full-coverage imaging in a short-wave infrared wave band.
However, the atomic layer deposition of the existing quantum dot detector is carried out on the surface of C60, the known quality is best in a mode of firstly water source and then tin source, but the C60 material is a hydrophobic material, so that the water source cannot be uniformly and densely paved on the surface of C60, the SnOx deposition quality of the first few (ten) cycles is very low, and the generated defects influence the overall quality of an electron transport layer, so that the detection performance of the detector is negatively influenced.
Content of the application
In view of the above, the present application provides a quantum dot detector and a method of manufacturing the quantum dot detector. The quality of the n-type electron transmission layer is improved, the detection performance of the detector is integrally improved, and the stability of the device is improved.
In a first aspect, a method for manufacturing a quantum dot detector is provided, including:
Providing a substrate;
Sequentially preparing a bottom electrode, an electron blocking layer, a P-type hole transport layer, a light absorption layer and a sacrificial layer on the substrate;
preparing a hydrophilic layer on the surface of one side of the sacrificial layer far away from the substrate, wherein the hydrophilic layer is made of WOx;
preparing an n-type electron transport layer on the surface of one side of the hydrophilic layer far away from the sacrificial layer, wherein the hydrophilic layer is used for improving the uniformity and compactness of the n-type electron transport layer;
and preparing a top electrode on the surface of one side of the n-type electron transport layer far away from the hydrophilic layer.
In one embodiment, the preparing the n-type electron transport layer on the surface of the hydrophilic layer far from the sacrificial layer includes:
And circularly and alternately depositing H2 O and Sn sources on the hydrophilic layer to prepare the n-type electron transport layer.
In one embodiment, the hydrophilic layer material is WO3.
In one embodiment, preparing a hydrophilic layer on a surface of the sacrificial layer on a side remote from the substrate comprises:
Heating a tungsten boat by adopting a thermal evaporation mode, and preparing a WOx film on the surface of one side of the sacrificial layer far away from the substrate;
Wherein the thermal evaporation speed is 0.001-0.003nm/s, and the thickness of the WOx film is 1-1.5nm.
In one embodiment, the tungsten boat is heated by thermal evaporation, and a WOx film is prepared on the surface of the sacrificial layer, which is far away from the substrate, and then the method further comprises the following steps:
And performing plasma cleaning on the WOx film.
In one embodiment, cyclically alternating deposition of H2 O and Sn sources on the hydrophilic layer to produce the n-type electron transport layer comprises:
and adopting an atomic layer deposition mode, taking TDMASn (tetra (dimethylamino) tin) as a Sn source, and circularly and alternately depositing H2 O and the Sn source on the hydrophilic layer to obtain a SnO2 film, thereby preparing the n-type electron transport layer.
In an embodiment, the material of the bottom electrode and the top electrode is ITO;
The material of the electron blocking layer is NiOX;
The P-type hole transport layer is made of PbS-EDT;
The light absorption layer is made of PbS-I/Br;
The material of the sacrificial layer is C60.
In a second aspect, the application provides a quantum dot detector, which sequentially comprises a bottom electrode, an electron blocking layer, a P-type hole transport layer, a light absorption layer, a sacrificial layer, a hydrophilic layer, an n-type electron transport layer and a top electrode from bottom to top;
the hydrophilic layer is made of WOx and is used for improving the uniformity and compactness of the n-type electron transport layer.
In one embodiment, the hydrophilic layer material is WO3.
In an embodiment, the material of the bottom electrode and the top electrode is ITO;
The material of the electron blocking layer is NiOX;
The P-type hole transport layer is made of PbS-EDT;
The light absorption layer is made of PbS-I/Br;
The material of the sacrificial layer is C60.
According to the scheme, a hydrophilic layer is arranged on the surface of the sacrificial layer C60, the material of the hydrophilic layer is WOx, then H2 O and Sn sources are circularly and alternately deposited (H2 O is firstly deposited) on the hydrophilic layer, after a water source is deposited on the hydrophilic layer, the contact angle of water (the contact angle of water is 6 degrees according to an experimental result) can be greatly reduced, the uniformity and compactness of an atomic layer deposited film can be improved, the quality of an n-type electron transport layer is improved, and the detection performance of a detector is integrally improved.
In addition, a layer of hydrophilic layer is arranged, the material of the hydrophilic layer is WOx, the hydrophilic layer is extremely strong, a large number of hydroxyl groups are arranged on the surface of the hydrophilic layer, the deposition and close arrangement of a water source are facilitated, the deposition film can keep high uniformity and compactness in the whole circulation process, and the transmission performance of the electron transmission layer can be effectively improved, so that the detection performance of a device is improved. In addition, the introduction of the tungsten oxide interface layer and the improvement of the quality of the electron transport layer can inhibit the migration of halogen ions (I-) to a certain extent, and the stability of the device is improved.
The foregoing description is only an overview of the present application, and is intended to be implemented in accordance with the teachings of the present application in order that the same may be more clearly understood and to make the same and other objects, features and advantages of the present application more readily apparent.
Detailed Description
Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. In addition, in the following description, descriptions of well-known structures and techniques are omitted so as not to unnecessarily obscure the concepts of the present disclosure.
Various structural schematic diagrams according to embodiments of the present disclosure are shown in the drawings. The figures are not drawn to scale, wherein certain details are exaggerated for clarity of presentation and may have been omitted. The shapes of the various regions, layers and relative sizes, positional relationships between them shown in the drawings are merely exemplary, may in practice deviate due to manufacturing tolerances or technical limitations, and one skilled in the art may additionally design regions/layers having different shapes, sizes, relative positions as actually required.
The quantum dot detector of the present application will be described in detail with reference to the accompanying drawings.
Referring to fig. 1, fig. 1 is a schematic flow chart of a method for manufacturing a quantum dot detector according to an embodiment of the application, which is characterized by comprising:
Step S11, providing a substrate.
The substrate material may be a glass substrate.
And step S12, sequentially preparing a bottom electrode, an electron blocking layer, a P-type hole transport layer, a light absorption layer and a sacrificial layer on the substrate.
In one embodiment, the bottom electrode layer material is indium tin oxide, ITO. Specifically, an indium tin oxide film is sputtered on a substrate by a magnetron sputtering method, and the indium tin oxide film is patterned by a laser etching/photoetching/nanoimprint process, so that a bottom electrode is formed. After the bottom electrode is prepared, the bottom electrode layer may be further cleaned, for example, by sequentially cleaning the bottom electrode layer with pure water, ethanol, and N, N-dimethylformamide solution DMF.
An electron blocking layer is disposed on the bottom electrode. The material of the electron blocking layer is NiOx. And carrying out vacuum magnetron sputtering on the Li NiO target material on the bottom electrode layer so as to prepare the electron blocking layer. Specifically, the distance between the target and the substrate is set to be 80cm, sputtering is carried out by adopting a radio frequency mode, argon is introduced to enable the pressure of a cabin to be about 2.0Pa, the sputtering power to be 100-200W and the sputtering time to be 3-20min, and a NiOx film with the thickness of about 20nm is obtained, so that an electron blocking layer is formed.
And a P-type hole transport layer is arranged on the electron blocking layer. The P-type layer material is PbS, and specifically, the P-type layer material is PbS-EDT (ethanedithiol ligand passivated PbS). In one embodiment, the method comprises the steps of performing operation in a fume hood, dissolving PbS CQD (colloidal quantum dots) with an absorption peak of 880nm in n-octane to prepare a quantum dot solution with the concentration of 40mg/ml, dispersing the EDT solution in acetonitrile to prepare a ligand solution with the concentration of 0.01% by mass of EDT, spin-coating a layer of the quantum dot solution (spin-coating speed is 2500-5000r/min, such as 4000r/min, spin-coating acceleration is 500-2000r/s, spin-coating time is 10-30s, such as 20 s) in a solid-phase exchange manner, dripping the ligand solution on a quantum dot solution film, standing for 30s, waiting for ligand exchange to be completed, and then washing the surface twice with acetonitrile to obtain a PbS-EDT film with the thickness of about 20nm, thereby obtaining a P-type hole transport layer.
And preparing a light absorption layer on the P-type hole transport layer, wherein the light absorption layer is made of PbS-I/Br (halogen ion passivated PbS). The specific preparation method of the light absorption layer comprises the following steps:
1) The PbS colloid quantum dots used for preparing the light absorption layer of the photoelectric detector are synthesized by a cation exchange method. Specifically, thioacetamide is firstly used as a sulfur source, zinc stearate is used as a zinc source, zinc sulfide quantum dots are synthesized, lead chloride is used as a lead source, cation exchange is carried out, and the absorption peak of PbS CQD is controlled by controlling the reaction time. The PbS CQD synthesized by the method is wrapped by oleic acid ligand, the interval between quantum dots is too large, and the problem of low mobility exists. Therefore, ligand exchange is needed, long-chain oleic acid ligand is replaced by short-chain iodine and bromine monoatomic ligand, and the electrical property of PbS CQD is enhanced.
2) Ligand exchange is carried out in a glove box under nitrogen atmosphere, specifically, pbS CQD synthesized by a cation exchange method is dissolved in n-octane at a concentration of 10mg/ml to obtain a quantum dot solution for standby. PbI2 and PbBr2 solid drugs were weighed by a balance and mixed with N, N-Dimethylformamide (DMF) solution, and dissolved by shaking thoroughly to prepare ligand solutions having PbI2 and PbBr2 concentrations of 0.0267mmol/ml and 0.0115mmol/ml, respectively. The quantum dot solution and the ligand solution are filtered and mixed according to the volume ratio of 1:1 by using a syringe and a filter head with the aperture of 0.22 mu m, and are fully oscillated to carry out ligand exchange, after standing, pbS CQD of iodine and bromine atom ligands is in a lower DMF polar phase, an upper n-octane solvent becomes transparent, and the upper solution is removed. In order to reduce the content of residual oleic acid, adding equal amount of n-octane, mixing, oscillating and cleaning, removing the upper liquid after layering, and repeating the cleaning process twice. And finally, subpackaging the DMF solution containing PbS CQD at the lower layer into a centrifuge tube, centrifuging at 9000r/min for 3min, removing the solution after centrifuging, and placing the residual precipitate, namely the PbS CQD wrapped by the iodine and bromine atom ligand, into a low-pressure drying box for further removing the residual solvent for later use.
3) Adding the dried PbS CQD quantum dot solid into the existing quaternary dispersion system (DMF: DMSO: BTA: 3-pyridylmethylamine=350ul: 250ul: 3700 ul:30 ul) with the concentration of 400mg/ml, fully oscillating and dispersing, and then coating at the rotating speed of 2500r/min for 40s to obtain a PbS-I/Br film with the thickness of about 250nm, thereby preparing the light absorption layer.
And preparing a sacrificial layer on the light absorption layer, wherein the material of the sacrificial layer is C60. And (3) placing the device with the prepared light absorption layer on a thermal evaporation instrument, coating by using a thermal evaporation mode, heating C60 by a tungsten boat, keeping the evaporation speed at 0.005-0.015 nm/s, and preparing C60 with the thickness of about 10-40nm, such as 15nm, so as to prepare the sacrificial layer.
And S13, preparing a hydrophilic layer on the surface of one side of the sacrificial layer far away from the substrate, wherein the hydrophilic layer is made of WOx.
In one embodiment, a tungsten boat is heated by thermal evaporation, and a WOx film is prepared on the surface of one side of the sacrificial layer far away from the substrate, wherein the thermal evaporation speed is 0.001-0.003nm/s, and the thickness of the WOx film is 1-1.5nm. Further, plasma cleaning of the WOx film can further increase its hydroxylation level.
In one embodiment, the hydrophilic layer material is WO3.
And S14, preparing an n-type electron transport layer on the surface of one side of the hydrophilic layer far away from the sacrificial layer, wherein the hydrophilic layer is used for improving the uniformity and compactness of the n-type electron transport layer.
And circularly and alternately depositing H2 O and Sn sources on the hydrophilic layer to prepare the n-type electron transport layer. Specifically, by adopting an atomic layer deposition mode, TDMASn (tetra (dimethylamino) tin) is used as a Sn source, and H2 O and the Sn source are circularly and alternately deposited on the hydrophilic layer to obtain a SnO2 film, so that the n-type electron transport layer is prepared. In atomic layer deposition, the temperature of a tin source is set to be 60 ℃ and the temperature of a substrate is set to be 90 ℃ so as to fully carry out the reaction as much as possible. And growing for 250 cycles to obtain a SnO2 film with the thickness of about 40nm, thereby obtaining the n-type electron transport layer.
Referring to fig. 2 a-2 b, experiments show that, in the case of the sacrificial layer C60 being a hydrophobic material, the cyclic alternating deposition of the H2 O and Sn sources (the first deposition of the H2 O) on the C60 during the atomic layer deposition can result in that the water source cannot be uniformly and densely spread on the surface of the C60, as shown in fig. 2a, when the water source is deposited on the surface of the C60, a large contact angle (the contact angle of water is 91.8 ° according to the experimental result) is generated, which can result in that the quality of the finally deposited n-type electron transport layer is very low, and the generated defects affect the overall quality of the n-type electron transport layer, thereby negatively affecting the detection performance of the detector. According to the scheme, a hydrophilic layer is arranged on the surface of the sacrificial layer C60, the material of the hydrophilic layer is WOx, then H2 O and Sn sources are circularly and alternately deposited (H2 O is firstly deposited) on the hydrophilic layer, as shown in fig. 2b, after a water source is deposited on the hydrophilic layer, the contact angle of water is greatly reduced (according to the experimental result, the contact angle of water is 6 degrees), the uniformity and compactness of an atomic layer deposited film are improved, the quality of an n-type electron transport layer is improved, and the detection performance of a detector is integrally improved.
In addition, a layer of hydrophilic layer is arranged, the material of the hydrophilic layer is WOx, the hydrophilic layer is extremely strong, a large number of hydroxyl groups are arranged on the surface of the hydrophilic layer, the deposition and close arrangement of a water source are facilitated, the deposition film can keep high uniformity and compactness in the whole circulation process, and the transmission performance of the electron transmission layer can be effectively improved, so that the detection performance of a device is improved. In addition, the introduction of the tungsten oxide interface layer and the improvement of the quality of the electron transport layer can inhibit the migration of halogen ions (I-) to a certain extent, and the stability of the device is improved.
And S15, preparing a top electrode on the surface of one side of the n-type electron transport layer far away from the hydrophilic layer.
The material of the top electrode is Indium Tin Oxide (ITO). The top electrode is coated by magnetron sputtering, and the target material is indium-doped tin oxide. The sputtering power is 100w-200w, and the sputtering time is 10-30 minutes.
Referring to fig. 3, fig. 3 is a schematic structural diagram of an embodiment of a quantum dot detector according to the present application, which specifically includes a bottom electrode 111, an electron blocking layer 112, a p-type hole transporting layer 113, a light absorbing layer 114, a sacrificial layer 115, a hydrophilic layer 118, an n-type electron transporting layer 116, and a top electrode 117 from bottom to top. The electron blocking layer 112 is arranged on the bottom electrode 111, the p-type hole transport layer 113 is arranged on one side of the electron blocking layer 112 away from the bottom electrode 111, the light absorption layer 114 is arranged on one side of the p-type hole transport layer 113 away from the bottom electrode 111, the sacrificial layer 115 is arranged on one side of the light absorption layer 114 away from the bottom electrode 111, the n-type electron transport layer 116 is arranged on one side of the sacrificial layer 115 away from the bottom electrode 111, and the top electrode 117 is arranged on one side of the n-type electron transport layer 116 away from the bottom electrode 111.
The material of the bottom electrode 111 is the same as that of the top electrode 117, and is an indium tin oxide film.
The material of the n-type electron transport layer 116 is SnO2.
Wherein the material of the sacrificial layer 115 is C60.
The P-type hole transport layer is made of PbS-EDT (ethanedithiol ligand passivated PbS);
The light absorbing layer 114 is made of PbS-I/Br (halogen ion passivated PbS) and is capable of absorbing photon energy under 1550nm light irradiation to generate an optical signal. The electron blocking layer 112, the p-type hole transport layer 113, the light absorbing layer 114, the sacrificial layer 115, and the n-type electron transport layer 116 form ohmic contacts between the bottom electrode 111 and the top electrode 117. The electron blocking layer 112, the p-type hole transport layer 113, the light absorbing layer 114, the sacrificial layer 115, and the n-type electron transport layer 116 form a p-i-n structure. Under light irradiation at 1550nm, the light absorbing layer 114 will generate electrons along the sacrificial layer 115 to the n-type electron transport layer 116 and vacancies to the p-type hole transport layer 113. The electron blocking layer 112 prevents electrons from traveling back from the light absorbing layer 114 to the p-type hole transport layer 113. The p-type hole transport layer 113 and the n-type electron transport layer 116 form a p-n junction (light emitting diode structure), and the p-type hole transport layer 113 generates carriers, and the built-in potential of the initial built-in electric field starts to change with the increase of the bias voltage. When the p-type hole transport layer 113 is fully depleted, the photocurrent is maximized, and the initial dark current and the photocurrent are subtracted to obtain a net photocurrent, and the optical signal per unit area is the responsivity of 1550nm light.
In the application, the hydrophilic layer material is WOx, which is used for improving the uniformity and compactness of the n-type electron transport layer. In particular, the hydrophilic layer material is WO3.
Experiments show that when the sacrificial layer C60 is a hydrophobic material and the atomic layer is deposited, H2 O and Sn sources are circularly and alternately deposited (H2 O is deposited firstly) on the surface of C60, which can lead to that a water source cannot be uniformly and densely paved on the surface of C60, as shown in fig. 2a, when the water source is deposited on the surface of C60, a large contact angle (the contact angle of water is 91.8 degrees according to the experimental result) can be generated, the quality of the finally deposited n-type electron transport layer is very low, and the generated defects influence the overall quality of the n-type electron transport layer, so that the detection performance of the detector is negatively influenced. According to the scheme, a hydrophilic layer is arranged on the surface of the sacrificial layer C60, the material of the hydrophilic layer is WOx, then H2 O and Sn sources are circularly and alternately deposited (H2 O is firstly deposited) on the hydrophilic layer, as shown in fig. 2b, after a water source is deposited on the hydrophilic layer, the contact angle (the contact angle of water is 6 degrees according to an experimental result) is greatly reduced, the uniformity and compactness of an atomic layer deposited film are improved, the quality of an n-type electron transport layer is improved, and the detection performance of a detector is integrally improved.
In addition, a layer of hydrophilic layer is arranged, the material of the hydrophilic layer is WOx, the hydrophilic layer is extremely strong, the deposition and close arrangement of a water source are facilitated, the high uniformity and the high compactness can be kept in the whole circulation process, and the transmission performance of the electron transmission layer can be effectively improved, so that the detection performance of a device is improved. In addition, the introduction of the tungsten oxide interface layer and the improvement of the quality of the electron transport layer can inhibit the migration of halogen ions (I-) to a certain extent, and the stability of the device is improved.
The algorithms and displays presented herein are not inherently related to any particular computer, virtual system, or other apparatus. Various general-purpose systems may also be used with the teachings herein. The required structure for a construction of such a system is apparent from the description above. In addition, the present application is not directed to any particular programming language. It will be appreciated that the teachings of the present application described herein may be implemented in a variety of programming languages, and the above description of specific languages is provided for disclosure of enablement and best mode of the present application.
In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the application may be practiced without these specific details. In some instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.
Similarly, it should be appreciated that in the foregoing description of exemplary embodiments of the application, various features of the application are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects.
Those skilled in the art will appreciate that the modules in the apparatus of the embodiments may be adaptively changed and disposed in one or more apparatuses different from the embodiment. The modules or units or components of the embodiments may be combined into one module or unit or component and, furthermore, they may be divided into a plurality of sub-modules or sub-units or sub-components. All of the features disclosed in this specification (including the abstract and drawings), and all of the processes or units of any method or apparatus so disclosed, may be combined in any combination, except combinations where at least some of such features and/or processes or units are mutually exclusive. Each feature disclosed in this specification (including the accompanying abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise.
Furthermore, those skilled in the art will appreciate that while some embodiments herein include some features but not others included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the application and form different embodiments.
It should be noted that the above-mentioned embodiments illustrate rather than limit the application. Any reference signs placed between parentheses shall not be construed as limiting the claim. The word "comprising" does not exclude the presence of elements or steps not listed in the application. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The application may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In an embodiment in which several means are recited, several of these means may be embodied by one and the same item of hardware. The use of the words first, second, third, etc. do not denote any order. These words may be interpreted as names.