Up-conversion device, up-conversion imager and preparation method
By adding a quantum dot absorbing layer in the upconversion device and adjusting the layer thickness, the problem of the proportion of electrons and holes is solved, and the luminous efficiency and imaging quality are improved.
Patent Information
- Application Number
- CN202411058445.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-02
- Publication Date
- 2024-12-13
Smart Images
Figure CN119133192A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of optoelectronic technology, and in particular to an up-conversion device and a preparation method thereof. Background Art
[0002] Upconversion luminescence is a luminescence technology that converts light with a longer wavelength (such as infrared light) into light with a shorter wavelength (such as visible light and ultraviolet light). By converting low-energy signals into high-energy signals, upconversion imaging systems can enhance imaging sensitivity and resolution, thereby obtaining clearer images under low-light conditions. The luminescence efficiency of upconversion devices in the prior art is low. Summary of the invention
[0003] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides an up-conversion device capable of improving luminous efficiency.
[0004] The present invention also provides a method for preparing the above-mentioned up-conversion device.
[0005] The present invention also provides an up-conversion imager comprising a plurality of the above-mentioned up-conversion devices.
[0006] According to the first aspect of the present invention, the up-conversion device includes a substrate, an anode layer, a first quantum dot absorption layer, a hole transport layer, a quantum dot material light-emitting layer, an electron transport layer, a second quantum dot absorption layer and a cathode layer which are stacked in sequence, and the thickness of the first quantum dot absorption layer is thinner than the thickness of the second quantum dot absorption layer.
[0007] According to the up-conversion device of the embodiment of the present invention, at least the following beneficial effects are achieved: the electrons in the up-conversion device are provided by the circuit, and the holes are provided by the quantum dot absorption layer. In the existing up-conversion device, there is no quantum dot absorption layer between the cathode layer and the electron transport layer, and the electrons of the circuit are directly transmitted and gathered to the light-emitting layer. The existing up-conversion device has the problem that the light-emitting layer of the quantum dot material has more electrons and fewer holes. The ratio of the two carriers (electrons and holes) in the existing up-conversion device is large, which leads to low efficiency of device light emission. The up-conversion device of the embodiment of the present invention can block part of the electrons from the circuit by adding a quantum dot absorption layer between the electron transport layer and the cathode layer, thereby reducing the number of electrons gathered in the light-emitting layer of the quantum dot material, and setting the thickness of the first quantum dot absorption layer thinner than the second quantum dot absorption layer can ensure that the second quantum dot absorption layer can still absorb enough external photon energy to generate photogenerated electrons although it is at the far light end, thereby reducing the imbalance of the two carriers and improving the light-emitting efficiency.
[0008] According to some embodiments of the present invention, the ratio of the thickness of the first quantum dot absorption layer to the thickness of the second quantum dot absorption layer is 1:5.
[0009] According to some embodiments of the present invention, the material of the anode layer includes at least one of ITO, IGZO, gold nanofilm, silver nanofilm and aluminum nanofilm; and / or the thickness of the anode layer is 70-300 nm.
[0010] According to some embodiments of the present invention, the material of the first quantum dot absorption layer is AX quantum dots, wherein A is any one of Pb, Cd, Ag, and Hg, and X is any one of S, Se, and Te; and / or the thickness of the first quantum dot absorption layer is 20 to 30 nm.
[0011] According to some embodiments of the present invention, the material of the second quantum dot absorption layer is AX quantum dots, wherein A is any one of Pb, Cd, Ag, and Hg, and X is any one of S, Se, and Te; and / or the thickness of the second quantum dot absorption layer is 100 to 200 nm.
[0012] According to some embodiments of the present invention, the material of the quantum dot material light-emitting layer includes at least one of CdSe quantum dots, CdS quantum dots, InAlAs / AlGaAs quantum dots and InP quantum dots; and / or the thickness of the quantum dot material light-emitting layer is 15 to 40 nm.
[0013] According to some embodiments of the present invention, the conduction band range of the material of the hole transport layer is between -1.7 eV and -3.2 eV, and the valence band range is between -4.5 eV and -5.7 eV; and / or the thickness of the hole transport layer is 20 to 50 nm.
[0014] According to some embodiments of the present invention, the conduction band range of the material of the electron transport layer is between -3.5 eV and -4.4 eV, and the valence band range is between -5.5 eV and -9.7 eV; and / or the thickness of the electron transport layer is 20 to 50 nm.
[0015] According to the preparation method of the second aspect embodiment of the present invention, for manufacturing the up-conversion device of the first aspect embodiment of the present invention, the preparation method comprises the following steps: sequentially preparing an anode layer, a first quantum dot absorption layer, a hole transport layer, a quantum dot material light-emitting layer, an electron transport layer, a second quantum dot absorption layer and a cathode layer on a substrate.
[0016] According to the preparation method of the embodiment of the present invention, at least the following beneficial effects are achieved: the electrons in the up-conversion device are provided by the circuit, and the holes are provided by the quantum dot absorption layer. In the existing up-conversion device, there is no quantum dot absorption layer between the cathode layer and the electron transport layer, and the electrons of the circuit are directly transmitted and gathered to the light-emitting layer. The existing up-conversion device has the problem that the light-emitting layer of the quantum dot material has more electrons and fewer holes. The ratio of the two carriers (electrons and holes) in the existing up-conversion device is large, which leads to low efficiency of device light emission. The up-conversion device manufactured by the preparation method of the embodiment of the present invention can block part of the electrons from the circuit by adding a quantum dot absorption layer between the electron transport layer and the cathode layer, thereby reducing the number of electrons in the light-emitting layer of the quantum dot material, and setting the thickness of the first quantum dot absorption layer thinner than the second quantum dot absorption layer can ensure that the second quantum dot absorption layer can still absorb enough external photon energy to generate photogenerated electrons although it is at the far light end, thereby reducing the imbalance of the two carriers and improving the light-emitting efficiency.
[0017] An up-conversion imager according to an embodiment of the third aspect of the present invention comprises a plurality of up-conversion devices according to embodiments of the present invention arranged in an array.
[0018] The upconversion imager according to the embodiment of the present invention has at least the following beneficial effects: the upconversion device according to the embodiment of the present invention can block part of the electrons from the circuit by adding a quantum dot absorption layer between the electron transport layer and the cathode layer, thereby reducing the number of electrons in the light-emitting layer of the quantum dot material, and setting the thickness of the first quantum dot absorption layer thinner than the second quantum dot absorption layer can ensure that although the second quantum dot absorption layer is at the far light end, it can still absorb enough external photon energy to generate photogenerated electrons, thereby reducing the imbalance of the two carriers, thereby improving the luminous efficiency, thereby improving the luminous efficiency of the upconversion imager including the upconversion device according to the embodiment of the present invention.
[0019] According to some embodiments of the present invention, the preparation of the hole transport layer includes the following steps: dissolving the material of the hole transport layer in toluene to form a solution so that the concentration of the material of the hole transport layer in the solution is 15 to 30 mg / mL; then using a spin coating method to coat the solution on the first quantum dot absorption layer to form a thin film with a thickness of 20 to 50 nm; and performing thermal annealing on the thin film to convert the thin film into a hole transport layer.
[0020] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein:
[0022] Figure 1 is an overall structural diagram of an up-conversion device according to an embodiment of the present invention;
[0023] Figure 2 is a schematic diagram of an up-conversion device according to an embodiment of the present invention when there is no light;
[0024] Figure 3 is a schematic diagram of an up-conversion device according to an embodiment of the present invention when there is light;
[0025] Figure 4 Schematic diagram of light direction and energy absorption;
[0026] Figure 5 This is an energy absorption diagram when the thickness ratio of the first quantum dot absorption layer to the second quantum dot absorption layer is 1:5;
[0027] Figure 6 It is a statistical diagram of energy absorption of the up-conversion device of an embodiment of the present invention after multiple tests.
[0028] Reference numerals: substrate 101 , anode layer 102 , first quantum dot absorption layer 103 , hole transport layer 104 , quantum dot material light-emitting layer 105 , electron transport layer 106 , second quantum dot absorption layer 107 , cathode layer 108 . DETAILED DESCRIPTION
[0029] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.
[0030] In the description of the present invention, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., and orientations or positional relationships indicated are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.
[0031] In the description of the present invention, "several" means more than one, "many" means more than two, "greater than", "less than", "exceed", etc. are understood to exclude the number itself, and "above", "below", "within", etc. are understood to include the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.
[0032] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.
[0033] In the description of the present invention, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.
[0034] refer to Figure 1The up-conversion device according to the first embodiment of the present invention includes a substrate 101, an anode layer 102, a first quantum dot absorption layer 103, a hole transport layer 104, a quantum dot material light-emitting layer 105, an electron transport layer 106, a second quantum dot absorption layer 107 and a cathode layer 108 stacked in sequence from bottom to top, and the thickness of the first quantum dot absorption layer 103 is thinner than the thickness of the second quantum dot absorption layer 107. The cathode layer 108 and the anode layer 102 are used to form a current loop to receive external input current; the substrate 101 is used as the basis of the up-conversion device to provide physical support for other layers; the first quantum dot absorption layer 103 and the second quantum dot absorption layer 107 are used to absorb light of a specific wavelength and convert it into photogenerated electrons and photogenerated holes. At the same time, when there is no external energy radiation, the first quantum dot absorption layer 103 and the second quantum dot absorption layer 107 can also play a role in blocking electrons and holes; the hole transport layer 104 is used to improve the injection efficiency of holes; the electron transport layer 106 is used to transport electrons; the quantum dot material light-emitting layer 105 is used for photogenerated electrons and photogenerated holes to recombine here and then release energy to emit visible light. In the existing up-conversion device with a single absorption layer structure, only the first quantum dot absorption layer 103 is provided, the electrons are provided by the circuit, the holes are provided by the first quantum dot absorption layer 103, and the electrons of the circuit are directly transmitted to the quantum dot material light-emitting layer 105. The existing up-conversion device has the problem that the quantum dot material light-emitting layer 105 has more electrons and fewer holes. The ratio of the two carriers (electrons and holes) in the existing up-conversion device is large, which leads to low efficiency of device light emission. However, the up-conversion device of the embodiment of the present invention adds a second quantum dot absorption layer 107 between the electron transport layer 106 and the cathode layer 108. The second quantum dot absorption layer 107 can block part of the electrons from the circuit, reducing the number of electrons gathered in the quantum dot material light-emitting layer 105, and the thickness of the first quantum dot absorption layer 103 is set thinner than the second quantum dot absorption layer 107 to ensure that the second quantum dot absorption layer 107, although at the far end of the light, can still absorb enough external photon energy to generate photogenerated electrons, thereby reducing the imbalance of the two carriers, thereby improving the light-emitting efficiency.
[0035] It should be noted that in the prior art, the up-conversion device with a single absorption layer structure is only provided with the first quantum dot absorption layer 103, so the external electrons will flow directly from the cathode layer 108 to the electron transport layer 106 and then gather in the quantum dot material light-emitting layer 105. At this time, there are also unactivated holes in the first quantum dot absorption layer 103, and there is only a hole transport layer 104 between the electrons and the holes, which is relatively thin. Even in the absence of infrared light, when the power is high, the electrons may tunnel and radiate and recombine with the holes, thereby causing light emission, resulting in a larger dark state light emission. In the up-conversion device of the embodiment of the present invention, the electrons gather in the second quantum dot absorption layer 107, and the holes gather in the first quantum dot absorption layer 103. There is an electron transport layer 106, a hole transport layer 104 and a quantum dot material light-emitting layer 105 between the electrons and the holes, which greatly reduces the possibility of light emission caused by electron tunneling due to power on. This makes the dark state light emission of the double-sided absorption device smaller than that of the single-sided device, improves the light-to-dark ratio, and reduces the probability of error occurrence.
[0036] Figure 2 and Figure 3 is a working principle diagram of an up-conversion device according to an embodiment of the present invention, Figure 2 It can be seen that when there is no light, the electrons and holes in the first quantum dot absorption layer 103 and the second quantum dot absorption layer 107 are in a relatively stable energy level state, and the quantum dot material light-emitting layer 105 is also in a low energy level state and is not excited; Figure 3 It can be seen that after being exposed to light (where NIR stands for near infrared light, which is the spectrum used in the embodiment of the present invention. Specifically, the embodiment of the present invention uses light with a wavelength of 970nm. In other embodiments of the present invention, other spectra such as mid-infrared light can also be used as a single-sided illumination source), photons of a specific wavelength are absorbed by the first quantum dot absorption layer 103 and the second quantum dot absorption layer 107 to generate photogenerated holes and photogenerated electrons. When the electrons and holes reach the light-emitting layer, they release energy through a recombination process. This energy is emitted in the form of photons to form visible light or radiation in other bands.
[0037] refer to Figure 5 In some embodiments of the present invention, the ratio of the thickness of the first quantum dot absorption layer 103 to the thickness of the second quantum dot absorption layer 107 is 1:5. Figure 6 , Figure 6 The PbS1 in the embodiment is the first quantum dot absorption layer 103, and the PbS2 is the second quantum dot absorption layer 107. Figure 6In the embodiment, the second quantum dot absorption layer 107 is fixedly set to 5 layers, and then the number of layers of the first quantum dot absorption layer 103 is changed, so as to simulate the absorption of energy by the first quantum dot absorption layer 103 and the second quantum dot absorption layer 107. It should be noted that the number of layers mentioned in the article refers to the number of times the spin coating or coating is performed during the processing. One spin coating or coating process is performed, that is, one layer of the first quantum dot absorption layer 103 or the second quantum dot absorption layer 107 is processed. It can be seen that when the first quantum dot absorption layer 10 When the layer ratio of the first quantum dot absorption layer 103 to the second quantum dot absorption layer 107 is 0.5 layers:5 layers, the energy of the absorbed photons is closest to 1:1. The second best result is a thickness ratio of 1 layer:5 layers, and the energy of the absorbed photons is close to 1:1. Considering the actual processing situation, the minimum number of processing layers is one layer, that is, the first quantum dot absorption layer 103 with a thickness of 20 to 30 nm. The thickness of the up-conversion device cannot be too large, so the thickness ratio of the first quantum dot absorption layer 103 to the second quantum dot absorption layer 107 is set to 1:5 during the final processing. In this way, the energy of the absorbed photons of the first quantum dot absorption layer 103 and the second quantum dot absorption layer 107 can be made as close to 1:1 as possible in actual situations, while the reference Figure 2 and Figure 3 After absorbing photons, the first quantum dot absorption layer 103 and the second quantum dot absorption layer 107 will generate photogenerated holes and photogenerated electrons. Therefore, when the energy of the photons absorbed by them is close to 1:1, the number of photogenerated holes and photogenerated electrons generated is also close to 1:1, thereby improving the luminous efficiency and luminous brightness of the up-conversion device.
[0038] It should be noted that Figure 5 and Figure 6 The simulation results produced by Setfos software were used.
[0039] It should be noted that Figure 4 is a schematic diagram of energy absorption. Figure 4 The upper number of each layer represents the conduction band position of the layer, and the lower number represents the valence band position of the layer. The units of conduction band and valence band are eV. Free electrons and free holes move in the conduction band and valence band respectively. 1x and 5x represent that the ratio of the thickness of the first quantum dot absorption layer 103 to the thickness of the second quantum dot absorption layer 107 is set to 1:5. The chemical formula in the figure represents the materials used in each layer in the embodiments of the present invention. In some embodiments of the present invention, other materials as shown below may also be used.
[0040] In some embodiments of the present invention, the material of the anode layer 102 includes at least one of ITO (indium tin oxide), IGZO (indium gallium zinc oxide), gold nanofilm, silver nanofilm and aluminum nanofilm; and / or, the thickness of the anode layer 102 is 70 to 300 nm. ITO has high conductivity and high transparency, can effectively transport current and allow a large amount of light to pass through; while IGZO has a higher carrier mobility, can more effectively transport charges, has good uniformity, and can ensure the uniform distribution of current in the device. Gold nanofilm, silver nanofilm and aluminum nanofilm also have high conductivity and high transparency, so the anode layer 102 material uses at least one of ITO, IGZO, gold nanofilm, silver nanofilm and aluminum nanofilm. It should be noted that the thickness of the anode layer 102 can be 70nm, 100nm, 300nm. When the thickness of the anode layer 102 is less than 70nm, the anode layer 102 is too thin and has poor conductivity, and light will be more scattered during propagation, resulting in reduced light absorption efficiency; when the thickness of the anode layer 102 is greater than 300nm, the anode layer 102 is too thick and the resistance increases, resulting in reduced current transmission efficiency, and an overly thick anode layer 102 will block more light, resulting in reduced light absorption efficiency, and at the same time will increase the size of the entire up-conversion device, which is not conducive to miniaturization and integration.
[0041] In some embodiments of the present invention, the material of the first quantum dot absorption layer 103 is AX quantum dots, wherein A is any one of Pb (lead), Cd (cadmium), Ag (silver), Hg (mercury), and X is any one of S (sulfur), Se (selenium), and Te (tellurium); and / or, the thickness of the first quantum dot absorption layer 103 is 20 to 30 nm. The combination of the above materials has the advantages of a wide wavelength absorption range, being able to make full use of multi-band light, and achieving efficient energy conversion. Specifically, the first quantum dot absorption layer 103 has an absorption wavelength of 750 nm to 5000 nm for infrared light, wherein infrared light of wavelengths such as 750 nm, 950 nm, and 5000 nm can be absorbed. Among them, the preferred material is PbS quantum dots, which have a wide wavelength absorption range, can make full use of multi-band light, and realize efficient energy conversion. PbS quantum dots have a large Bohr radius and a significant quantum effect, and the emission spectrum covers the near-infrared band range, has high chromatic purity, and good stability. Moreover, the band structure of PbS quantum dots can be adjusted by controlling the synthesis conditions, thereby optimizing the optical performance. It should be noted that the thickness of the first quantum dot absorption layer 103 can be 20nm, 25nm, 30nm, etc. When the thickness of the first quantum dot absorption layer 103 is less than 20nm, the first quantum dot absorption layer 103 is too thin, inconvenient to process, insufficient light absorption, resulting in low light energy utilization, and in the quantum dot absorption layer, electrons and holes need to be separated and migrated to the corresponding electrodes. If it is too thin, the migration distance of electrons and holes is too short, resulting in an increased probability of electrons and holes recombination during the migration process, thereby reducing the efficiency of charge separation. When the thickness of the first quantum dot absorption layer 103 is greater than 30 nm, the first quantum dot absorption layer 103 is too thick, which increases the resistance of electrons and holes during migration, reduces the charge transfer efficiency, and causes the size of the entire up-conversion device to become larger, which is not conducive to miniaturization and integration.
[0042] In some embodiments of the present invention, the material of the second quantum dot absorption layer 107 is AX quantum dots, wherein A is any one of Pb (lead), Cd (cadmium), Ag (silver), Hg (mercury), and X is any one of S (sulfur), Se (selenium), and Te (tellurium); and / or, the thickness of the second quantum dot absorption layer 107 is 100 to 200 nm. The combination of the above materials has the advantages of a wide wavelength absorption range, being able to make full use of multi-band light, and achieving efficient energy conversion. Specifically, the second quantum dot absorption layer 107 has an absorption wavelength of 750 nm to 5000 nm for infrared light, wherein infrared light of wavelengths such as 750 nm, 950 nm, and 5000 nm can be absorbed. Among them, the preferred material is PbS quantum dots. PbS quantum dots have a wide wavelength absorption range, can make full use of multi-band light, and achieve efficient energy conversion. PbS quantum dots have a large Bohr radius and a significant quantum effect. The emission spectrum covers the near-infrared band range, has high chromatic purity, and good stability. Moreover, the band structure of PbS quantum dots can be adjusted by controlling the synthesis conditions to optimize the optical performance. It should be noted that the thickness of the second quantum dot absorption layer 107 can be 100nm, 125nm, and 200nm. When the thickness of the second quantum dot absorption layer 107 is less than 100nm, the light absorption efficiency of the second quantum dot absorption layer 107 is insufficient, resulting in low light energy utilization. When the thickness of the second quantum dot absorption layer 107 is greater than 200nm, the second quantum dot absorption layer 107 is too thick, resulting in increased resistance of electrons and holes in the migration process, reducing the charge transfer efficiency, and causing the size of the entire up-conversion device to become larger, which is not conducive to miniaturization and integration.
[0043] It should be noted that in the prior art, PbS quantum dots are used as quantum dot absorption layers, and the PbS material absorbs a portion of the visible light emitted after receiving infrared rays, thereby reducing the light extraction efficiency of the up-conversion device. In the up-conversion device in the embodiment of the present invention, the first quantum dot absorption layer 103 is arranged at the near light end, and the second quantum dot absorption layer 107 is arranged at the far light end. On the premise of ensuring a sufficient number of holes, the absorption of PbS for the emitted visible light is reduced by reducing the thickness of the first quantum dot absorption layer 103, thereby improving the light extraction efficiency.
[0044] In some embodiments of the present invention, the material of the quantum dot material light-emitting layer 105 includes at least one of CdSe (cadmium selenide) quantum dots, CdS (cadmium sulfide) quantum dots, lnAlAs (aluminum gallium indium arsenide) / AlGaAs (gallium aluminum arsenide) quantum dots and lnP (indium phosphide) quantum dots; and / or, the thickness of the quantum dot material light-emitting layer 105 is 15 to 40 nm. The above materials are selected as the quantum dot material light-emitting layer 105 because the above materials all have strong absorption and light emission characteristics in the ultraviolet-visible spectrum, can effectively absorb light energy and convert it into fluorescent emission, thereby achieving efficient photoelectric conversion, and have a high quantum yield, can effectively convert absorbed photons into electrons-holes, and improve the photoelectric conversion efficiency of the up-conversion device. It should be noted that the thickness of the quantum dot material light-emitting layer 105 can be 15nm, 25nm, or 40nm. When the thickness of the quantum dot material light-emitting layer 105 is less than 15nm, the quantum dot material light-emitting layer 105 is too thin and the light-emitting intensity is insufficient to meet the application requirements of the up-conversion device. When the thickness of the quantum dot material light-emitting layer 105 is greater than 40nm, electrons and holes need to travel a longer distance during the migration process, which increases the chance that they release heat energy rather than light energy, resulting in reduced energy conversion efficiency.
[0045] It should be noted that, in some embodiments of the present invention, the wavelength range of visible light emitted by the quantum dot material light emitting layer 105 is between 400 nm and 700 nm.
[0046] In some embodiments of the present invention, the conduction band range of the material of the hole transport layer 104 is between -1.7eV and -3.2eV, and the valence band range is between -4.5eV and -5.7eV; and / or, the thickness of the hole transport layer 104 is 20 to 50nm. Preferred materials include at least one of: NiOx (nickel oxide), PTAA (polytriarylamine), PEDOT (poly 3,4-ethylenedioxythiophene), PSS (polystyrene sulfonic acid), TFB (polymer optoelectronic material, CAS No. 223569-31-1), P3HT (polymer of 3-hexylthiophene) and TPD (thienopyrrole diketo organic conjugated material). The materials in the above conduction band range and valence band range are selected as the hole transport layer 104 because the above materials have excellent hole transport capabilities and can effectively transport holes from the light-emitting layer to the anode, thereby improving the charge transfer efficiency of the up-conversion device. It should be noted that the thickness of the hole transport layer 104 can be 20nm, 30nm, or 50nm. When the thickness of the hole transport layer 104 is less than 20nm, the hole transport layer 104 is too thin and has poor stability, which can easily lead to leakage or recombination of charges during the transmission process, thereby reducing the photoelectric conversion efficiency; when the thickness of the hole transport layer 104 is greater than 50nm, the hole transport layer 104 is too thick, which increases the path length and transmission time of hole transmission, thereby reducing the photoelectric conversion efficiency.
[0047] In some embodiments of the present invention, the conduction band range of the material of the electron transport layer 106 is between -3.5eV and -4.4eV, and the valence band range is between -5.5eV and -9.7eV; and / or, the thickness of the electron transport layer 106 is 20 to 50nm. Preferred materials include at least one of ZnO (zinc oxide), TiO2 (titanium dioxide), PCBM (fullerene derivative), SnO2 (tin dioxide) and Alq3 (8-hydroxyquinoline aluminum). The materials in the above conduction band range and valence band range are selected as the electron transport layer 106 because the above materials have excellent conductivity, can effectively reduce the electron recombination effect, thereby improving the photoelectric conversion efficiency of the up-conversion device, and have good chemical stability, thereby maintaining stable electron transport performance and extending the service life of the device. It should be noted that the thickness of the electron transport layer 106 can be 20nm, 30nm, or 50nm. When the thickness of the electron transport layer 106 is less than 20 nm, the electron transport layer 106 is too thin and cannot effectively prevent the recombination of electrons and holes, thereby reducing the photoelectric efficiency. Moreover, being too thin will reduce the stability of the electron transport layer 106. When the thickness of the electron transport layer 106 is greater than 50 nm, the electron transport layer 106 is too thick, which increases the path length of electron transport and reduces the photoelectric conversion efficiency. Moreover, an overly thick electron transport layer 106 will also increase the series resistance of the up-conversion device and reduce the overall performance of the up-conversion device.
[0048] It should be noted that, in some embodiments of the present invention, the material used for the substrate 101 includes at least one of quartz, glass, and PMMA (polymethyl methacrylate). The above materials are selected as the substrate 101 because the above materials have good optical transparency, can maintain the integrity and intensity of light, thereby improving the efficiency of the up-conversion process, and the above materials have high impact resistance and scratch resistance. This mechanical stability ensures the reliability and durability of the up-conversion device during use.
[0049] The preparation method according to the second aspect of the present invention is used to manufacture the up-conversion device of the first aspect of the present invention, and the preparation method includes the following steps: an anode layer 102, a first quantum dot absorption layer 103, a hole transport layer 104, a quantum dot material light-emitting layer 105, an electron transport layer 106, a second quantum dot absorption layer 107 and a cathode layer 108 are sequentially prepared on a substrate 101. In the existing up-conversion device with a single absorption layer structure, only the first quantum dot absorption layer 103 is provided, the electrons are provided by the circuit, and the holes are provided by the first quantum dot absorption layer 103. The electrons of the circuit are directly transmitted and gathered to the quantum dot material light-emitting layer 105. The existing up-conversion device has the problem of more electrons and fewer holes. The difference in the ratio of the two carriers (electrons and holes) in the existing up-conversion device is large, which leads to low efficiency of device light emission. The up-conversion device manufactured by the preparation method of the embodiment of the present invention has a second quantum dot absorption layer 107 added between the electron transport layer 106 and the cathode layer 108. The second quantum dot absorption layer 107 can block part of the electrons from the circuit, thereby reducing the number of electrons in the quantum dot material light-emitting layer 105. Setting the thickness of the first quantum dot absorption layer 103 to be thinner than the second quantum dot absorption layer 107 can ensure that although the second quantum dot absorption layer 107 is at the far light end, it can still absorb enough external photon energy to generate photogenerated electrons, thereby reducing the imbalance of the two carriers and improving the luminous efficiency.
[0050] In some embodiments of the present invention, the preparation of the hole transport layer 104 includes the following steps: dissolving the material of the hole transport layer 104 in toluene to form a solution, so that the concentration of the material of the hole transport layer 104 in the solution is 15-30 mg / mL; then the solution is applied to the first quantum dot absorption layer 103 by spin coating to form a thin film with a thickness of 20-50 nm; and the thin film is subjected to thermal annealing treatment to convert the thin film into the hole transport layer 104. Specifically, in some embodiments of the present invention, the thermal annealing treatment is performed by controlling the temperature at 100-200°C and the holding time at 5-20 minutes. Such treatment can improve the morphology and transport characteristics of the hole transport layer 104, optimize the charge transport capacity of the hole transport layer 104, and further improve the overall performance of the up-conversion device.
[0051] It should be noted that, specifically, the preparation method comprises the following steps:
[0052] First, a substrate 101 material with a thickness of 200 μm to 1 mm is prepared, and pre-processed by cleaning and drying;
[0053] Then, a 70-300 nm thick anode layer 102 is deposited on the substrate 101 by magnetron sputtering. The magnetron sputtering method can ensure uniform film formation and a high deposition rate, thereby improving the quality of the anode layer 102.
[0054] Then, the PbS quantum dot material is uniformly dispersed in an n-octane solvent to form a slurry with a concentration of 50 mg / mL to 300 mg / mL by a solution method, and a first quantum dot absorption layer 103 with a thickness of 20 nm to 30 nm is formed on the anode layer 102 by a spin coating method. The spin coating method can well control the thickness of the first quantum dot absorption layer 103 to meet the preparation requirements of different thicknesses;
[0055] Then, the hole transport layer 104 is prepared according to the steps in the above embodiment;
[0056] Then, a quantum dot material light-emitting layer 105 is prepared. Taking CdSe material as an example, CdSe quantum dots are uniformly dissolved in toluene solvent to form a light-emitting layer slurry with a concentration of 3 mg / mL to 15 mg / mL. The CdSe quantum dots are used as a raw material to spin-coat a quantum dot material light-emitting layer 105 with a thickness of 15 nm to 40 nm on the hole transport layer 104, and then a thermal annealing treatment is performed to convert the film into a quantum dot material light-emitting layer 105. Specifically, in some embodiments of the present invention, the thermal annealing treatment is performed by controlling the temperature at 80 to 110° C. and the holding time at 5 to 10 minutes. Such a treatment can improve the film properties of the quantum dot material light-emitting layer 105, and enhance the light-emitting efficiency and stability of the quantum dot material light-emitting layer 105. At the same time, the thermal annealing treatment can also effectively suppress unfavorable light emission, making the spectrum purer and more balanced.
[0057] Then, the electron transport layer 106 is prepared by a deposition method, with a deposition thickness of 20 nm to 50 nm;
[0058] Then, the second quantum dot absorption layer 107 is prepared by the same method as the first quantum dot absorption layer 103, but the thickness of the prepared layer is 100-200 nm;
[0059] Then, a cathode layer 108 is prepared on the second quantum dot absorption layer 107. At least one material selected from gold, silver and aluminum is used, and an evaporation deposition method is used to form the cathode layer 108 with a thickness of 100 nm to 200 nm.
[0060] In this way, the up-conversion device is prepared. It should be noted that the spin coating method in the above-mentioned preparation method of each layer can also be prepared by coating method, deposition method and the like, and can be adjusted according to actual production needs.
[0061] According to an embodiment of the third aspect of the present invention, an upconversion imager includes a plurality of upconversion devices of the present invention arranged in an array. The upconversion device of the embodiment of the present invention, by adding a second quantum dot absorption layer 107 between the electron transport layer 106 and the cathode layer 108, the second quantum dot absorption layer 107 can block part of the electrons from the circuit, reducing the number of electrons in the quantum dot material light-emitting layer 105, and setting the thickness of the first quantum dot absorption layer 103 thinner than the second quantum dot absorption layer 107 can ensure that the second quantum dot absorption layer 107, although at the far end of the light, can still absorb enough external photon energy to generate photogenerated electrons, thereby reducing the imbalance of the two carriers, thereby improving the luminous efficiency, thereby improving the luminous efficiency of the upconversion imager including the upconversion device of the embodiment of the present invention.
[0062] It should be noted that, in some embodiments of the present invention, the specific imaging process of the up-conversion imager is: by arranging multiple up-conversion device arrays to make large-area devices, and then driving them through TFT (thin film transistor) chips or CMOS (complementary metal oxide semiconductor) chips, it is possible to achieve visible light imaging of infrared images.
[0063] It should be noted that, in some embodiments of the present invention, the number of pixels of the up-conversion imager can be increased from 100*100 to 8k pixels, and the up-conversion imager can also be made into an imager with a flexible effect.
[0064] The embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the purpose of the present invention. In addition, the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.
Claims
1. An up-conversion device, characterized in that It includes a substrate, an anode layer, a first quantum dot absorption layer, a hole transport layer, a quantum dot material light-emitting layer, an electron transport layer, a second quantum dot absorption layer and a cathode layer which are stacked in sequence, wherein the thickness of the first quantum dot absorption layer is thinner than that of the second quantum dot absorption layer.
2. The up-conversion device according to claim 1, characterized in that: The ratio of the thickness of the first quantum dot absorption layer to the thickness of the second quantum dot absorption layer is 1:
5.
3. The up-conversion device according to claim 1, characterized in that: The material of the anode layer includes at least one of ITO, IGZO, gold nanofilm, silver nanofilm and aluminum nanofilm; and / or, The thickness of the anode layer is 70-300 nm.
4. The up-conversion device according to claim 1, wherein: The material of the first quantum dot absorption layer is AX quantum dots, wherein A is any one of Pb, Cd, Ag, and Hg, and X is any one of S, Se, and Te; and / or, The thickness of the first quantum dot absorption layer is 20-30 nm.
5. The up-conversion device according to claim 1, characterized in that: The material of the second quantum dot absorption layer is AX quantum dots, wherein A is any one of Pb, Cd, Ag, and Hg, and X is any one of S, Se, and Te; and / or, The thickness of the second quantum dot absorption layer is 100-200 nm.
6. The up-conversion device according to claim 1, characterized in that: The material of the quantum dot material light-emitting layer includes at least one of CdSe quantum dots, CdS quantum dots, InAlAs / AlGaAs quantum dots and InP quantum dots; and / or, The thickness of the quantum dot material light-emitting layer is 15-40 nm.
7. The up-conversion device according to claim 1, characterized in that: The conduction band range of the material of the hole transport layer is between -1.7 eV and -3.2 eV, and the valence band range is between -4.5 eV and -5.7 eV; and / or The thickness of the hole transport layer is 20-50 nm.
8. The up-conversion device according to claim 1, wherein: The conduction band range of the material of the electron transport layer is between -3.5 eV and -4.4 eV, and the valence band range is between -5.5 eV and -9.7 eV; and / or, The thickness of the electron transport layer is 20-50 nm.
9. A preparation method, characterized in that: The preparation method is used to manufacture the up-conversion device according to any one of claims 1 to 8, and the preparation method comprises the following steps: The anode layer, the first quantum dot absorption layer, the hole transport layer, the quantum dot material light-emitting layer, the electron transport layer, the second quantum dot absorption layer and the cathode layer are sequentially prepared on the substrate.
10. An up-conversion imager, characterized in that: The up-conversion imager comprises a plurality of up-conversion devices according to any one of claims 1 to 8 arranged in an array.