Near-infrared LED device and preparation method thereof

Abstract

The invention provides a near-infrared LED device and a preparation method thereof. The preparation method comprises the steps that a P-type light-emitting layer is manufactured and formed on a transparent conductive substrate layer, the P-type light-emitting layer is manufactured and formed through a co-evaporation method and a low-temperature annealing process by adopting copper-cadmium-zinc-tin-selenium as a raw material and adopting sodium fluoride as an additive; forming an N-type buffer layer on the P-type light-emitting layer; forming a conductive layer on the N-type buffer layer; and forming a top electrode layer on the conductive layer. According to the method, high-quality growth of the P-type light-emitting layer can be ensured, the light-emitting efficiency of the device is improved, the cost is reduced, meanwhile, light can be emitted from the transparent conductive substrate layer side, and the light-emitting area is increased.

Description

Technical Field

[0001] The present application belongs to the technical field of optoelectronic devices, and specifically relates to a near-infrared LED device and a preparation method thereof. Background Art

[0002] Short-wave infrared (SWIR) spectroscopy, with its strong penetrating power and thermal effects, is becoming a rapid, convenient, non-invasive, and non-destructive analytical tool. It exhibits excellent spectral properties, including being completely invisible to the human eye, high penetration through haze, smoke, and dust, and low light scattering and absorption in biological tissue. Consequently, its application in areas such as product sorting, moisture detection, chemical analysis, bioimaging, and night vision monitoring has attracted widespread attention. Currently, commercially available short-wave infrared (SWIR) LED devices are primarily based on Group III-V materials and their derivatives, as well as colloidal quantum dot-based materials (such as InGaAsP and AlInGaAs). Their excellent optoelectronic properties have made them a mainstream choice. However, InGaAsP is typically grown on an InP substrate. The lattice mismatch in the high indium content of InGaAsP can lead to stress and defects in the device. Furthermore, the relatively expensive InP substrate further increases the production cost of InGaAsP-based LEDs, significantly increasing production costs.

[0003] Cu2Cd x Zn 1-x SnSe4 is a kesterite photovoltaic material with high earth abundance and no toxicity. Adjusting the Cd content can change the band gap width while having a high absorption coefficient. The traditional preparation process usually adopts a two-step method: first depositing the precursor at low temperature, and then performing selenization annealing at high temperature to obtain a dense crystal structure. x Zn 1-x SnSe4 belongs to the category of thin film deposition and can be prepared by sputtering, co-evaporation or solution self-assembly + selenization annealing. Compared with III-V materials, Cu2Cd x Zn 1-x SnSe4 process does not require expensive metal organic precursors and high vacuum equipment, the process temperature is relatively low, and the potential cost is low. x Zn 1-x When SnSe4 ultra-thin film is subjected to high-temperature selenization annealing on the substrate, FTO suffers from conductivity loss, surface morphology deterioration, and interface chemical side reactions that affect device performance.

[0004] Specifically, the current high temperature annealing process has the following shortcomings: Under the high temperature condition of 550±50℃, Cu2Cd x Zn 1-xThe Sn and Se in the SnSe4 absorber layer are prone to volatilization. At the same time, the Sn in the FTO film layer will also react with the Se in the absorber layer or the H2Se in the annealing atmosphere to generate volatile SnSe / SnSe2, resulting in Sn vacancies and holes in the film, a significant increase in resistance, and a decrease in substrate conductivity, thereby weakening the device performance. The SnSe gas generated by the reaction escapes from the film layer under thermal drive, and the F and O elements in the FTO may diffuse into the absorber layer, changing the interface carrier concentration and potential barrier, further damaging the electrical properties. High-temperature annealing will also promote the growth and reorientation of FTO grains, increase surface roughness, intensify light scattering, and significantly reduce the average transmittance, especially in the visible and near-infrared range. In addition, due to the difference in thermal expansion coefficients between the FTO film and the glass substrate, thermal stress can induce microcracks or local delamination; in a Se-rich or H2Se atmosphere, SnO2 may also be partially reduced to low-valent tin oxide or metallic tin, changing the conductive mechanism of the film layer and accelerating its degradation. Annealing Cu2Cd in the range of 400–500°C x Zn 1-x SnSe4 grains can grow fully, and lower temperatures can reduce the side reactions between Sn and H2Se in FTO, avoiding the micropores and voids caused by the volatilization of SnSe / SnSe2, thereby maintaining the conductivity and light transmittance of the FTO film.

[0005] Currently, for Cu2Cd x Zn 1-x Devices made of SnSe4 materials generally use soda-lime glass or silicon as a substrate, and magnetron sputtering is used to deposit a molybdenum layer as the bottom electrode for deriving electrical signals. However, the Mo bottom electrode is opaque, and light from the other side will be blocked by the electrode, reducing the light-emitting area. Summary of the Invention

[0006] The technical problem solved by the present application is: how to provide a low-cost near-infrared LED device with high luminous efficiency and large luminous area and a preparation method thereof.

[0007] The present application provides a method for preparing a near-infrared LED device, the method comprising:

[0008] Forming a P-type light-emitting layer on a transparent conductive substrate layer, wherein the P-type light-emitting layer uses copper, cadmium, zinc, tin, and selenium as raw materials and sodium fluoride as an additive, and is formed by a co-evaporation method and a low-temperature annealing process;

[0009] forming an N-type buffer layer on the P-type light-emitting layer;

[0010] forming a conductive layer on the N-type buffer layer;

[0011] A top electrode layer is formed on the conductive layer.

[0012] Optionally, the transparent conductive substrate layer includes glass and a transparent conductive substrate stacked together, and the transparent conductive substrate is bonded to the P-type light-emitting layer.

[0013] Optionally, the method for manufacturing the P-type light-emitting layer includes:

[0014] A copper-cadmium-zinc-tin-selenium layer is deposited on a transparent conductive substrate layer by a co-evaporation method;

[0015] Then, the copper-cadmium-zinc-tin-selenium layer is subjected to a low-temperature annealing treatment, wherein the low-temperature annealing treatment includes a low-temperature pretreatment and a selenization treatment;

[0016] Finally, a cooling process is performed to form a P-type light-emitting layer.

[0017] Optionally, the method of depositing a copper-cadmium-zinc-tin-selenium layer on a transparent conductive substrate layer by a co-evaporation method includes:

[0018] The transparent conductive substrate layer is placed into the MBE vacuum coating chamber and the vacuum range is controlled at 1×10 -5 Pa~1×10 - 4 Pa, adjust the temperature of Cu, Cd, Zn, Sn, Se, and NaF sources, and evaporate and deposit them together for 20 minutes to form a copper, cadmium, zinc, tin, and selenium layer on the transparent conductive substrate layer. The growth time of NaF is 2 minutes to 3 minutes.

[0019] Optionally, the low-temperature pretreatment comprises: raising the temperature of the copper-cadmium-zinc-tin-selenium layer from room temperature to 310° C. within 15 minutes, and then maintaining it at 310° C. for 60 minutes, with a H2Se concentration of 5% and a total pressure of 50 kPa;

[0020] The selenization treatment includes: raising the temperature of the copper-cadmium-zinc-tin-selenium layer from 310° C. to a predetermined temperature within 15 minutes, and then maintaining the predetermined temperature for 60 minutes, with a H 2 Se concentration of 5% and a total pressure of 50 kPa.

[0021] Optionally, the predetermined temperature ranges from 400°C to 500°C.

[0022] Optionally, the method of forming an N-type buffer layer on the P-type light-emitting layer includes:

[0023] The N-type buffer layer is formed by atomic layer deposition or chemical water bath deposition.

[0024] Optionally, the method of forming a conductive layer on the N-type buffer layer includes:

[0025] A conductive layer is formed on the N-type buffer layer by adopting a magnetron sputtering method.

[0026] Optionally, the method of forming an electrode layer on the conductive layer includes:

[0027] A top electrode layer is formed on the conductive layer by electron beam evaporation.

[0028] The present application discloses a near-infrared LED device, which is prepared by using the above-mentioned method for preparing a near-infrared LED device.

[0029] The present application provides a near-infrared LED device and a method for manufacturing the same, which have the following technical effects:

[0030] A P-type light-emitting layer can be formed on a transparent conductive substrate layer through a co-evaporation method and a low-temperature annealing process, which can ensure high-quality growth of the P-type light-emitting layer, improve the luminous efficiency of the device, and reduce costs. At the same time, light can be emitted from the transparent conductive substrate layer, thereby increasing the light-emitting area. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A near-infrared LED device according to one or more embodiments;

[0032] Figure 2 is a flow chart of a method for preparing a near-infrared LED device according to one or more embodiments;

[0033] Figure 3a 、 Figure 3b Spectral diagrams of near-infrared LED devices at different central wavelengths according to one or more embodiments;

[0034] Figure 4 is a scanning electron microscope image of a p-type light-emitting layer of a near-infrared LED device according to one or more embodiments. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solutions and advantages of this application more clearly understood, the following further describes this application in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0036] Before describing the various embodiments of the present application in detail, the technical concept of the present application will be briefly described first: Current near-infrared LED devices generally find it difficult to achieve low cost, high luminous efficiency, and a large luminous area. To this end, the present application provides a near-infrared LED device and a method for preparing the same. A P-type light-emitting layer is formed on a transparent conductive substrate layer by a co-evaporation method and a low-temperature annealing process. Copper, cadmium, zinc, tin, and selenium are used as raw materials, and sodium fluoride is used as an additive. This ensures high-quality growth of the P-type light-emitting layer, improves the luminous efficiency of the device, and reduces costs. At the same time, light can be emitted from the transparent conductive substrate layer, increasing the luminous area. The specific principles of the near-infrared LED device and its preparation method of the present application will be described below in conjunction with more embodiments.

[0037] Specifically, if Figure 1 As shown, the method for preparing the near-infrared LED device of the first embodiment includes the following steps:

[0038] Step S10: forming a P-type light-emitting layer 20 on the transparent conductive substrate layer 10, wherein the P-type light-emitting layer uses copper, cadmium, zinc, tin, and selenium as raw materials and sodium fluoride as an additive, and is formed by a co-evaporation method and a low-temperature annealing process;

[0039] Step S20 , forming an N-type buffer layer 30 on the P-type light emitting layer 20 ;

[0040] Step S30 , forming a conductive layer 40 on the N-type buffer layer 30 ;

[0041] Step S40 , forming a top electrode layer 50 on the conductive layer 40 .

[0042] In one or more embodiments, the transparent conductive substrate layer 10 includes a stacked glass 11 and a transparent conductive substrate 12, and the transparent conductive substrate 12 is bonded to the P-type light-emitting layer 20. For example, the material of the transparent conductive substrate 12 can be fluorine-doped tin oxide (FTO) or indium tin oxide (ITO).

[0043] In one or more embodiments, the method for manufacturing the P-type light-emitting layer includes: first, depositing a copper-cadmium-zinc-tin-selenium layer on the transparent conductive substrate layer 10 by a co-evaporation method; then performing a low-temperature annealing treatment on the copper-cadmium-zinc-tin-selenium layer, wherein the low-temperature annealing treatment includes a low-temperature pretreatment and a selenization treatment; and finally performing a cooling treatment to form a P-type light-emitting layer 20.

[0044] For example, the method for depositing a copper-cadmium-zinc-tin-selenium layer on a transparent conductive substrate layer by co-evaporation includes: placing the transparent conductive substrate layer into an MBE vacuum coating chamber, controlling the vacuum range to be 1×10 -5 Pa~1×10 -4Pa, adjust the temperature of Cu, Cd, Zn, Sn, Se, and NaF sources, and co-evaporate and deposit for 20 minutes to form a copper-cadmium-zinc-tin-selenium layer on the transparent conductive substrate layer. The growth time of NaF is 2 minutes to 3 minutes. Exemplarily, the low-temperature pretreatment includes: raising the temperature of the copper-cadmium-zinc-tin-selenium layer from room temperature to 310°C within 15 minutes, and then maintaining it at 310°C for 60 minutes, the H2Se concentration is 5%, and the total pressure is 50kPa. Exemplarily, the selenization treatment includes: raising the temperature of the copper-cadmium-zinc-tin-selenium layer from 310°C to a predetermined temperature within 15 minutes, and then maintaining it at the predetermined temperature for 60 minutes, the H2Se concentration is 5%, and the total pressure is 50kPa. The predetermined temperature range is 400°C-500°C.

[0045] For Cu2Cd under low temperature annealing process x Zn 1-x The grain growth problem of SnSe4 (0≤x<1) can be solved by introducing NaF as an additive in the absorption layer, which can effectively achieve the growth of high-quality crystals under low-temperature process, thereby improving the performance of the device.

[0046] In one or more embodiments, the method for forming the N-type buffer layer 30 on the P-type light-emitting layer 20 includes: using atomic layer deposition or chemical water bath deposition to form the N-type buffer layer 30. These two methods greatly reduce the non-radiative recombination between grain boundaries and enhance the radiative recombination between pn junctions, thereby improving the narrow bandgap Cu2Cd x Zn 1-x Luminous efficiency of SnSe4 LED devices.

[0047] Exemplarily, a method for forming an N-type buffer layer 30 by a chemical water bath method includes: first placing a sample in the center of a glass container, pouring a prepared reaction solution into the glass container, controlling the reaction temperature and time, depositing an N-type buffer layer 30 with a thickness of approximately 50 nm on the P-type light-emitting layer, and after the N-type buffer layer 30 is deposited, rinsing with deionized water, drying with nitrogen, and placing in a 100°C constant temperature oven for 2 minutes. Exemplarily, a method for forming an N-type buffer layer 30 by atomic layer deposition includes: placing a sample in the center of a cleaned atomic layer deposition chamber, adjusting the ratio of an oxygen source, a sulfur source, and a zinc source, introducing nitrogen as a protective gas, controlling the reaction temperature and time, depositing an N-type buffer layer 30 with a thickness of approximately 50 nm on the P-type light-emitting layer 20, and after the N-type buffer layer is deposited, flushing the surface with high-purity nitrogen.

[0048] In one or more embodiments, the conductive layer 40 is formed on the N-type buffer layer 30 by magnetron sputtering. For example, the sample obtained in the previous step is placed in a vacuum chamber, and the vacuum range is controlled to be 1×10 -5 Pa~1×10 -4Pa, a mixed gas of argon and oxygen was introduced, and the intrinsic zinc oxide target was sputtered on the sample at a power of 120W / 220W for 3 to 4 minutes, and then at a power of 350W for 13 to 14 minutes to form a conductive layer 40.

[0049] In one or more embodiments, the top electrode layer 50 is formed on the conductive layer 40 by electron beam evaporation. For example, the sample is placed with its back side facing downward in a vacuum chamber with a vacuum range of 1×10 -3 Pa~1×10 -2 Between Pa, the electron beam flow is turned on to evaporate Au or Ag electrodes in sequence to obtain a surface electrode layer with a thickness of 2000 nm, which serves as the top electrode of the device.

[0050] In this embodiment, the device structure is improved and copper-cadmium-zinc-tin-selenium (Cu2Cd x Zn 1-x SnSe4 (where 0≤x<1) p-type light-emitting layer is grown directly on the transparent conductive substrate layer. Compared with the opacity of the Mo substrate, the use of a transparent conductive substrate layer can achieve luminescence. Compared with traditional LED light sources, the device structure has no electrode obstruction and a larger luminous area. At the same time, the material is widely present in nature and is grown using co-evaporation equipment. It is simple to prepare and can be produced on a large scale. A low-temperature growth process is used to suppress the volatilization of Sn and Se and the formation of secondary phases, thereby maintaining the electrical and optical properties of the transparent conductive substrate layer, thereby improving the photoelectric performance of the device; at the same time, it reduces the heat treatment requirements, saves manufacturing energy consumption and simplifies the equipment. The thermal evaporation method is used to dope NaF while growing the absorption layer, and the appropriate annealing temperature is controlled to make the grains of the absorption layer grow to a suitable size, reduce the non-radiative recombination between the grain boundaries, enhance the radiative recombination between the pn junctions, thereby improving the narrow bandgap Cu2Cd x Zn 1-x The luminescence efficiency of the SnSe4LED device was also improved. A novel approach was also used for the n-type buffer layer, systematically reducing grain boundaries, interfaces, and point defects in the crystalline material, thereby increasing luminescence intensity. By improving the device structure, regulating the grain size of the p-type absorber layer, and modifying the growth process of the n-type buffer layer, this embodiment achieves lower cost than traditional devices while also improving device efficiency.

[0051] In order to verify the performance of the near infrared LED device of this embodiment, relevant tests were carried out. First, the test spectrum was obtained, such as Figure 3a and Figure 3b They represent the spectrum of different central wavelengths, and the lines of different colors represent the spectrum curves under different current intensities. It can be seen that Cu2Cd x Zn 1-xThe near-infrared LED device made of SnSe4 p-type layer material has an increasing luminous intensity as the current increases. Next, the multi-component planar array p-type light-emitting layer was characterized by scanning electron microscopy. The crystal quality before and after adding NaF was compared. It was found that the crystal growth was more uniform and dense after adding NaF, and the crystal surface was flatter. The scanning electron microscopy image is shown in Figure 4 . Figure 4 The upper left and lower left images in the middle are scanning electron microscope images of the p-type light-emitting layer grown without adding NaF; Figure 4 The upper right and lower right images in the middle are scanning electron microscope images of the p-type light-emitting layer grown after adding NaF.

[0052] The above describes in detail the specific implementation methods of the present application. Although some embodiments have been shown and described, those skilled in the art should understand that these embodiments can be modified and improved without departing from the principles and spirit of the present application, the scope of which is defined by the claims and their equivalents. These modifications and improvements should also be within the scope of protection of the present application.

Claims

1. A method for preparing a near-infrared LED device, characterized in that: The preparation method comprises: Forming a P-type light-emitting layer on a transparent conductive substrate layer, wherein the P-type light-emitting layer uses copper, cadmium, zinc, tin, and selenium as raw materials and sodium fluoride as an additive, and is formed by a co-evaporation method and a low-temperature annealing process; forming an N-type buffer layer on the P-type light-emitting layer; forming a conductive layer on the N-type buffer layer; A top electrode layer is formed on the conductive layer.

2. The method for preparing a near-infrared LED device according to claim 1, wherein: The transparent conductive substrate layer includes glass and a transparent conductive substrate that are stacked, and the transparent conductive substrate is bonded to the P-type light-emitting layer.

3. The method for preparing a near-infrared LED device according to claim 1, wherein: The method for manufacturing the P-type light-emitting layer includes: A copper-cadmium-zinc-tin-selenium layer is deposited on a transparent conductive substrate layer by a co-evaporation method; Then, the copper-cadmium-zinc-tin-selenium layer is subjected to a low-temperature annealing treatment, wherein the low-temperature annealing treatment includes a low-temperature pretreatment and a selenization treatment; Finally, a cooling process is performed to form a P-type light-emitting layer.

4. The method for preparing a near-infrared LED device according to claim 3, wherein: The method for depositing a copper-cadmium-zinc-tin-selenium layer on a transparent conductive substrate layer by a co-evaporation method comprises: The transparent conductive substrate layer is placed into the MBE vacuum coating chamber and the vacuum range is controlled at 1×10 -5 Pa~1×10 -4 Pa, adjust the temperature of Cu, Cd, Zn, Sn, Se, and NaF sources, and evaporate and deposit them together for 20 minutes to form a copper, cadmium, zinc, tin, and selenium layer on the transparent conductive substrate layer. The growth time of NaF is 2 minutes to 3 minutes.

5. The method for preparing a near-infrared LED device according to claim 3, wherein: The low-temperature pretreatment comprises: raising the temperature of the copper-cadmium-zinc-tin-selenium layer from room temperature to 310° C. within 15 minutes, and then maintaining it at 310° C. for 60 minutes, with a H2Se concentration of 5% and a total pressure of 50 kPa; The selenization treatment includes: raising the temperature of the copper-cadmium-zinc-tin-selenium layer from 310° C. to a predetermined temperature within 15 minutes, and then maintaining the predetermined temperature for 60 minutes, with a H 2 Se concentration of 5% and a total pressure of 50 kPa.

6. The method for preparing a near-infrared LED device according to claim 5, wherein: The predetermined temperature ranges from 400°C to 500°C.

7. The method for preparing a near-infrared LED device according to claim 1, wherein: The method for forming an N-type buffer layer on the P-type light-emitting layer includes: The N-type buffer layer is formed by atomic layer deposition or chemical water bath deposition.

8. The method for preparing a near-infrared LED device according to claim 1, wherein: The method for forming a conductive layer on the N-type buffer layer includes: A conductive layer is formed on the N-type buffer layer by adopting a magnetron sputtering method.

9. The method for preparing a near-infrared LED device according to claim 1, wherein: The method for forming an electrode layer on the conductive layer includes: A top electrode layer is formed on the conductive layer by electron beam evaporation.

10. A near-infrared LED device, characterized in that: The near-infrared LED device is prepared by the method for preparing a near-infrared LED device according to any one of claims 1 to 9.

Images