A Eu-doped SrHfS3 Luminescent Film and Its Preparation Method

Abstract

The present invention relates to the field of luminescent thin films in light-emitting diode devices. Although sulfide perovskites have advantages such as high stability, good electrical conductivity, and suitable for doping with rare-earth luminescent ions to emit light, there are problems such as the difficulty in preparing rare-earth-doped sulfide perovskite thin films. The present invention discloses a Eu-doped SrHfS3 luminescent thin film and a preparation method thereof, comprising the following steps: obtaining EuS powder through sulfidation and sintering it into a EuS target; co-sputtering based on a SrHfO3 target and a EuS target to obtain a precursor thin film; and performing a sulfidation treatment on the precursor thin film to obtain a Eu-doped SrHfS3 thin film. This preparation method is simple to operate, obtains divalent Eu ions using a reducing atmosphere, and realizes the efficient doping of Eu ions in sulfide perovskites by virtue of the advantages of sputtering. The obtained Eu-doped SrHfS3 luminescent thin film exhibits good crystallinity and luminescence characteristics, and has the potential to be used as a light-emitting layer in novel light-emitting diode devices.

Description

Technical Field

[0001] The present invention relates to the technical field of preparation of luminescent thin film materials, and particularly to an Eu-doped SrHfS3 luminescent thin film and a preparation method thereof. Background Art

[0002] For electro-luminescent devices such as light-emitting diodes, the luminescent layer thin film is a core component therein. In practical applications, the luminescent layer thin film is required to have good stability to match long-term operation, high-efficiency carrier transport to achieve non-radiative recombination of carriers such as holes and electrons, environmentally friendly constituent elements and high crustal abundance for sustainable utilization, and good luminescent properties to achieve high internal and external quantum efficiencies. Therefore, it is of great significance to explore new luminescent thin films that meet the above requirements.

[0003] SrHfS3 is a new type of sulfide perovskite semiconductor material. Current experimental results show that it has advantages such as high stability and good carrier transport characteristics, and its unique advantages such as environmentally friendly constituent elements and high crustal abundance are conducive to sustainable applications (refer to Patent ZL202210773468.9). Recently, it has been reported that by introducing rare earth Eu ions into sulfide perovskites, good luminescent properties can be achieved (Adv. Optical Mater. 2023, 2301977). The Eu-doped SrHfS3 material fully combines the advantages of high stability, excellent carrier transport of the sulfide perovskite SrHfS3 and the luminescence of Eu ions, and thus becomes a potential luminescent material with good development prospects in devices such as light-emitting diodes.

[0004] However, there is currently a lack of an effective preparation method for Eu-doped SrHfS3 thin films, which is a key factor restricting its application. This patent proposes a scheme of co-sputtering and sulfidation to achieve the preparation of Eu-doped SrHfS3 thin films with high crystallinity and high luminescence efficiency, including steps such as preparation of EuS powder and target, co-sputtering, and sulfidation treatment, which is an efficient technical scheme. Summary of the Invention

[0005] The purpose of the present invention is to obtain an Eu-doped SrHfS3 thin film with high crystallinity and high luminescence brightness, and a preparation method based on co-sputtering and sulfidation treatment is proposed.

[0006] To achieve the above purpose, the present invention adopts the following technical scheme:

[0007] A preparation method of an Eu-doped SrHfS3 luminescent thin film includes the following steps:

[0008] S1. Sulfurize the Eu2O3 raw material powder to obtain EuS powder;

[0009] S2. Press and sinter the EuS powder to obtain the EuS target;

[0010] S3. Based on the SrHfO3 target and the EuS target, deposit the precursor film by magnetron sputtering;

[0011] S4. Sulfurize the precursor film to obtain the Eu-doped SrHfS3 film;

[0012] In step S1, put the Eu2O3 powder into a quartz boat, place it in a tube furnace, use a mechanical pump to evacuate the tube furnace to below 0.1 Pa, introduce carbon disulfide and then carry out the sulfurization treatment. The pressure in the furnace is maintained at 30 Pa, the sulfurization temperature is 1000 °C, and the EuS powder is obtained after cooling to room temperature;

[0013] In step S2, grind and mix the polyvinyl alcohol and the EuS powder, put it into a tablet pressing mold with a diameter of 50 mm, carry out cold pressing under a pressure of 24 tons, and obtain a EuS wafer after pressure relief. Carry out vacuum sintering at 1100 °C for 1 hour, and obtain the EuS target after cooling to room temperature;

[0014] In step S3, put the SrHfO3 target and the EuS target into the sputtering chamber, use quartz as the substrate, evacuate the background vacuum of the magnetron sputtering system to below 0.001 Pa, the sputtering working gas is argon, the argon flow rate is 20 SCCM, the sputtering pressure is 1 Pa, the sputtering time is 2 h, the power of the SrHfO3 sputtering gun is 60 W, the power of the EuS sputtering gun is 20 W, and the Eu-doped SrHfS3 precursor film is obtained after sputtering;

[0015] In step S4, put the Eu-doped SrHfS3 precursor film obtained in step S3 into a tube furnace, evacuate to the background vacuum using a mechanical pump, introduce a sulfurizing gas for sulfurization, set the tube furnace to rise to the sulfurization temperature and keep it warm, and then obtain the Eu-doped SrHfS3 luminescent film after cooling to room temperature; the background vacuum should be below 0.1 Pa, the pressure in the furnace is 30 Pa after introducing the sulfurizing gas, and the sulfurization temperature is 1000 - 1050 °C; the sulfurizing gas is one of carbon disulfide gas and hydrogen sulfide gas;

[0016] Preferably, in steps S2 and S3, the thickness of the EuS target is 3 mm, and it is bonded with a copper backplane to facilitate heat dissipation and avoid target cracking.

[0017] Preferably, in step S4, the sulfurization time is greater than 4 h.

[0018] Preferably, after the sulfurization reaction, cool down to room temperature at a cooling rate of 5 °C / min.

[0019] The present invention provides a method for preparing an Eu-doped SrHfS3 luminescent thin film, which has the characteristics of simple operation and high raw material utilization. The beneficial effects of the present invention and the scientific principles behind them are as follows:

[0020] Beneficial effect 1: The required raw materials such as SrHfO3 target, Eu2O3 powder, carbon disulfide, hydrogen sulfide gas, etc. can be conveniently purchased on the market; the required tube furnace and magnetron sputtering equipment are also common industrial products on the market;

[0021] Beneficial effect 2: Magnetron sputtering is beneficial to the formation of high-quality thin films, and the obtained Eu-doped SrHfS3 luminescent thin film has good crystallinity and stability;

[0022] Beneficial effect 3: Considering that this material is an environmentally friendly lead-free perovskite material, it is more promising to be applied to new optoelectronic devices;

[0023] Beneficial effect 4: Considering that it is difficult for Eu ions to be doped into SrHfS3 in the traditional method, magnetron sputtering can be used to ionize and decompose the target raw materials, so that Eu ions can be easily incorporated into the SrHfS3 matrix, improving the doping efficiency and avoiding the introduction of other impurities at the same time;

[0024] Beneficial effect 5: Utilize the reducing property provided by the sulfide gas itself during the sulfidation process to reduce trivalent Eu ions to divalent Eu ions, generating the broad-spectrum luminescence unique to divalent Eu ions, rather than the characteristic narrow-spectrum luminescence of trivalent Eu ions. Description of the Drawings

[0025] Figure 1 is the flow chart of the method for preparing the Eu-doped SrHfS3 luminescent thin film of the present invention;

[0026] Figure 2 is the XRD pattern of the EuS powder prepared in step S1 of Example 1 of the present invention;

[0027] Figure 3 is the scanning electron microscope image and EDX energy spectrum of the EuS powder prepared in Example 1 of the present invention;

[0028] Figure 4 is the physical image of the EuS target prepared in Example 1 of the present invention;

[0029] Figure 5 is the physical image of the Eu-doped SrHfS3 thin film obtained after step S4 prepared in Example 1 of the present invention;

[0030] Figure 6 is the X-ray diffraction pattern of the Eu-doped SrHfS3 luminescent thin film prepared in Example 1 of the present invention;

[0031] Figure 7 X-ray photoelectron spectroscopy of the Eu-doped SrHfS3 luminescent thin film prepared in Example 1 of the present invention;

[0032] Figure 8 Fluorescence test spectrum of the Eu-doped SrHfS3 luminescent thin film prepared in Example 1 of the present invention;

[0033] Figure 9 Fluorescence lifetime diagram of the Eu-doped SrHfS3 luminescent thin film prepared in Example 1 of the present invention;

[0034] Figure 10 Tauc plot spectrum of the Eu-doped SrHfS3 luminescent thin film prepared in Example 1 of the present invention; Detailed implementation mode

[0035] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments.

[0036] Example 1

[0037] Step S1: Purchase commercial Eu2O3 powder, place the Eu2O3 powder in a quartz boat, and then put it into a tube furnace. Use a mechanical pump to evacuate the tube furnace to below 0.1 Pa, introduce carbon disulfide for sulfidation treatment, keep the pressure in the furnace at 30 Pa, and the sulfidation temperature at 1000 °C. After cooling to room temperature, obtain EuS powder; Step S2: Grind and mix polyvinyl alcohol and EuS powder, put it into a tablet die with a diameter of 50 mm, perform cold pressing under a pressure of 24 tons, and obtain a EuS wafer after pressure relief. Vacuum sinter at 1100 °C for 1 hour, and obtain a EuS target after cooling to room temperature; Step S3: Place the SrHfO3 target and EuS target in the sputtering chamber, use quartz as the substrate, evacuate the background vacuum of the magnetron sputtering system to below 0.001 Pa, the sputtering working gas is argon, the argon flow rate is 20 SCCM, the sputtering pressure is 1 Pa, the sputtering time is 2 h, the power of the SrHfO3 sputtering gun is 60 W, and the power of the EuS sputtering gun is 20 W. After sputtering, obtain a Eu-doped SrHfS3 precursor thin film; Step S4: Place the Eu-doped SrHfS3 precursor thin film obtained in Step S3 into a tube furnace, evacuate to the background vacuum using a mechanical pump, introduce a sulfiding gas for sulfidation, set the tube furnace to rise to the sulfidation temperature and keep it warm, and then obtain a Eu-doped SrHfS3 luminescent thin film after cooling to room temperature; The background vacuum should be below 0.1 Pa, the pressure in the furnace is 30 Pa after introducing the sulfiding gas, and the sulfidation temperature is 1000 °C; the sulfiding gas is carbon disulfide gas;

[0038] Figure 1It is the flow chart of the preparation method of Eu-doped SrHfS3 luminescent thin film according to the present invention;

[0039] Figure 2 It is the XRD pattern of the EuS powder prepared in step S1 of Example 1 of the present invention; it can be seen that the EuS powder prepared in step S1 has good crystallinity and purity;

[0040] Figure 3 It is the scanning electron microscope image and EDX energy spectrum of the EuS powder prepared in Example 1 of the present invention; it conforms to the expected element composition and there are no other impurities;

[0041] Figure 4 It is the physical picture of the EuS target prepared in Example 1 of the present invention;

[0042] Figure 5 It is the physical picture of the Eu-doped SrHfS3 thin film obtained after step S4 in Example 1 of the present invention; its surface is flat and the morphology is good;

[0043] Figure 6 It is the X-ray diffraction pattern of the Eu-doped SrHfS3 luminescent thin film prepared in Example 1 of the present invention; the Eu-doped SrHfS3 thin film shows good crystallinity and can match the standard card;

[0044] Figure 7 It is the X-ray photoelectron energy spectrum of the Eu-doped SrHfS3 luminescent thin film prepared in Example 1 of the present invention; the elements conform to the chemical ratio and expectations;

[0045] Figure 8 It is the fluorescence test spectrum of the Eu-doped SrHfS3 luminescent thin film prepared in Example 1 of the present invention; the luminescence shows a broad spectrum luminescence at 631 nm, which belongs to the luminescence of divalent Eu ions;

[0046] Figure 9 It is the fluorescence lifetime diagram of the Eu-doped SrHfS3 luminescent thin film prepared in Example 1 of the present invention; the average lifetime belongs to the normal Eu ion luminescence lifetime;

[0047] Figure 10 It is the Tauc plot diagram of the Eu-doped SrHfS3 luminescent thin film prepared in Example 1 of the present invention; this diagram shows that the band gap value of the Eu-doped SrHfS3 luminescent thin film is around 2.45 eV.

[0048] Example 2

[0049] Steps S1 - S3 are basically the same as steps S1 - S3 in Example 1;

[0050] Step S4: Place the SrHfS3:Eu precursor thin film obtained in step S3 into a tube furnace, evacuate it to a base vacuum using a mechanical pump, introduce a sulfiding gas for sulfidation, set the tube furnace to heat up to the sulfidation temperature and hold for a certain time, and then cool it to room temperature to obtain the SrHfS3:Eu luminescent thin film. The base vacuum should be lower than 0.1 Pa, the pressure inside the furnace after introducing the sulfiding gas is 30 Pa, and the sulfidation temperature is 1050 °C. The sulfiding gas is carbon disulfide gas.

[0051] The difference between Example 2 and Example 1 is that in step S4, the sulfidation temperature is increased to 1050 °C.

[0052] Example 3

[0053] Steps S1 - S3 are basically the same as steps S1 - S3 in Example 1.

[0054] Step S4: Place the SrHfS3:Eu precursor thin film obtained in step S3 into a tube furnace, evacuate it to a base vacuum using a mechanical pump, introduce a sulfiding gas for sulfidation, set the tube furnace to heat up to the sulfidation temperature and hold for a certain time, and then cool it to room temperature to obtain the SrHfS3:Eu luminescent thin film. The base vacuum should be lower than 0.1 Pa, the pressure inside the furnace after introducing the sulfiding gas is 30 Pa, and the sulfidation temperature is 1000 °C. The sulfiding gas is hydrogen sulfide gas.

[0055] The difference between Example 3 and the above Example 1 is that in step S4, hydrogen sulfide gas is used as the sulfiding gas.

[0056] The present invention provides a method for preparing SrHfS3:Eu luminescent thin films. Raw materials required, such as SrHfO3 targets, Eu2O3 powders, carbon disulfide, hydrogen sulfide, etc., and equipment such as tube furnaces can be conveniently purchased in the industrial market. The obtained SrHfS3:Eu luminescent thin films have good crystallinity and luminescence properties. Their elemental composition conforms to the chemical formula expression and expectations, and they exhibit good luminescence properties. The physical mechanism is that the SrHfS3 matrix absorbs light and transfers it to the luminescent center Eu ions, making it a highly potential sulfide perovskite luminescent thin film. In addition, considering that this material is an environmentally friendly and lead-free perovskite material with high crustal abundances of its constituent elements, it is more promising for applications in new luminescent devices.

[0057] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, making equivalent substitutions or changes should be covered within the protection scope of the present invention.

Claims

1. A method for preparing a SrHfS3-doped Eu-luminescent thin film, characterized in that: The following steps are involved: S1. Sulfiding the Eu2O3 raw material powder to obtain EuS powder; It is characterized in that in step S1, Eu2O3 powder is placed in a quartz boat, placed in a tube furnace, the tube furnace is evacuated to below 0.1Pa using a mechanical pump, and sulfurization treatment is performed after carbon disulfide is introduced, the pressure in the furnace is maintained at 30Pa, the sulfurization temperature is 1000°C, and EuS powder is obtained after cooling to room temperature; S2. The EuS powder is pressed and sintered to obtain a EuS target; The method is characterized in that, in step S2, polyvinyl alcohol and EuS powder are ground and mixed, put into a tablet pressing mold with a diameter of 50 mm, cold pressed under a pressure of 24 tons, and a EuS disc is obtained after the pressure is released, and vacuum sintered at 1100° C. for 1 hour, and then cooled to room temperature to obtain a EuS target; S3. Based on SrHfO3 target and EuS target, the precursor film is obtained by magnetron sputtering deposition; It is characterized in that in step S3, a SrHfO3 target material and a EuS target material are placed in a sputtering chamber, quartz is used as a substrate, the background vacuum of the magnetron sputtering system is evacuated to less than 0.001Pa, the sputtering working gas is argon, the argon flow rate is 20SCCM, the sputtering pressure is 1Pa, the sputtering time is 2h, the power of the SrHfO3 sputtering gun is 60W, the power of the EuS sputtering gun is 20W, and after the sputtering is completed, a SrHfS3 doped Eu precursor film is obtained; S4. Sulfurizing the precursor film to obtain a SrHfS3-doped Eu film; It is characterized in that in step S4, the SrHfS3-doped Eu precursor film obtained in step S3 is placed in a tubular furnace, a mechanical pump is used to evacuate to a background vacuum, a sulfiding gas is introduced for sulfidation, the tubular furnace is set to heat up to a sulfidation temperature and keep the temperature, and then the temperature is cooled to room temperature to obtain a SrHfS3-doped Eu luminescent film; It is characterized in that, in step S4, the background vacuum should be lower than 0.1Pa, the pressure in the furnace is 30Pa after the sulfurizing gas is introduced, and the sulfurizing temperature is 1000-1050°C; It is characterized in that, in step S4, the sulfiding gas is one of carbon disulfide gas and hydrogen sulfide gas.

2. The SrHfS3 doped Eu luminescent film prepared by the method for preparing the SrHfS3 doped Eu luminescent film as described in claim 1.

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