An electroluminescent device based on a TiO 2 :Er 3+ luminescent layer and a preparation method thereof

Abstract

The present invention discloses an electroluminescent device based on a TiO2:Er 3+ luminescent layer and a preparation method thereof, belonging to the technical field of rare earth doped semiconductor electroluminescence. The electroluminescent device successively includes an aluminum electrode, an n + -Si substrate, a TiO2:Er 3+ luminescent layer, a ZnO layer, and an ITO transparent electrode. The TiO2:Er 3+ luminescent layer is prepared by a sol-gel method. The present invention optimizes the doping concentration of Er 3+ ions in the TiO2:Er 3+ luminescent layer, and introduces a ZnO layer above the TiO2:Er 3+ luminescent layer as an electron blocking layer and a protective layer to further improve the electroluminescent performance related to Er 3+ ions.

Description

Technical Field

[0001] The present invention relates to the field of optoelectronic materials and optoelectronic devices, and particularly relates to an electroluminescent device based on a TiO 2 :Er 3+ luminescent layer and a preparation method thereof. Background Art

[0002] Rare earth Er 3+ ions have abundant metastable energy levels, and the energy level transition from its first excited state to the ground state ( 4 I 13 / 2 → 4 I 15 / 2 , ~1.55 μm) falls within the range of the lowest loss window of optical fiber communication. Er 3+ ion-doped wide bandgap semiconductor electroluminescent devices are compatible with modern silicon-based processes, and obtaining highly efficient Er 3+ ion-doped wide bandgap electroluminescent devices is of great significance for realizing silicon-based monolithic optoelectronic interconnection, and thus has attracted much attention from scientific researchers. Based on Er 3+ ion-doped SiO 2 thin film electroluminescent devices have made certain progress, but due to the insulation of SiO 2 , their turn-on voltage is relatively high and the luminous efficiency is low. Wide bandgap oxide semiconductor materials have high rare earth solubility, good conductivity and stable performance. Therefore, Er 3+ ion-doped wide bandgap oxide semiconductor luminescent layers have attracted extensive attention.

[0003] Titanium dioxide (TiO 2 ) as a wide bandgap oxide semiconductor material has the advantages of stable physical and chemical properties, low price, silicon-based compatibility, etc., and is considered an ideal matrix material for rare earth-doped electroluminescent devices. TiO 2 generally exhibits two stable crystal structures, anatase phase and rutile phase. Among them, rare earth-doped anatase phase TiO 2 as the luminescent layer of an electroluminescent device shows good electroluminescent performance. Although electroluminescent devices based on TiO 2 :Er 3+ luminescent layers have made certain progress, most of them are prepared by magnetron sputtering. When using the magnetron sputtering method to prepare related devices, the doping ratio of Er 3+ ions is not easy to control and the price is expensive. The sol-gel method for preparing thin film materials is simple, convenient to regulate and low in cost. Using the sol-gel method to prepare TiO 2 :Er 3+ luminescent layers can achieve large-area and low-cost production. Using the sol-gel method to prepare high-quality and highly efficient TiO2 :Er 3+ The light-emitting layer and the improved device structure are of great significance for improving the electroluminescence performance and stability of the device. Summary of the Invention

[0004] The technical problem to be solved by the present invention: When preparing an electroluminescent device based on a TiO 2 :Er 3+ light-emitting layer by magnetron sputtering, the doping ratio of Er 3+ ions is not easy to control, and the problem of high cost.

[0005] To solve the above technical problems, the present invention provides the following technical solutions:

[0006] An electroluminescent device based on a TiO 2 :Er 3+ light-emitting layer, which sequentially includes an aluminum electrode, an n + -Si substrate, a TiO 2 :Er 3+ light-emitting layer, a ZnO layer, and an ITO transparent electrode layer. The TiO 2 :Er 3+ light-emitting layer is prepared by the sol-gel method, and the magnetron-sputtered ZnO layer serves as an electron blocking layer and a protective layer.

[0007] Preferably, the Si substrate is a single-side polished heavily doped n + -Si substrate with a resistivity of 0.001 Ω·cm.

[0008] Preferably, the thickness of the TiO 2 :Er 3+ light-emitting layer prepared by the sol-gel method is 60-90 nm.

[0009] Preferably, the concentration of Er 2 :Er 3+ ions in the light-emitting layer is 0.5 mol%-5 mol%. 3+ Preferably, the thickness of the ZnO layer is 50-70 nm; the thickness of the ITO layer is 250-270 nm.

[0010] A method for preparing the above electroluminescent device, comprising the following steps:

[0011] (1) Mix anhydrous ethanol, tetrabutyl titanate, acetylacetone, and deionized water evenly according to a volume ratio of 20:7:3:1, add a little nitric acid to adjust the pH≈2, and accurately weigh Er(NO

[0012] (1) Mix anhydrous ethanol, tetrabutyl titanate, acetylacetone, and deionized water evenly according to a volume ratio of 20:7:3:1, add a little nitric acid to adjust the pH≈2, and accurately weigh Er(NO3 ) 3 ·5H 2 O is fully dissolved into the precursor solution, and then the mixed solution is placed in a 60 °C water bath environment and continuously stirred for 4 hours. After cooling and standing for 1 week, a uniform TiO 2 :Er 3+ gel is formed for standby;

[0013] (2) The silicon wafer squares cut into 1×1 cm 2 are cleaned using the RCA standard cleaning process;

[0014] (3) Measure 30 μl of the TiO 2 :Er 3+ gel prepared in step (1), and drop-coat it onto the cleaned n + -Si wafer. The rotation speed of the spin coater is set to 5000 revolutions per minute, and spin coating is performed for 60 s to form a uniform TiO 2 :Er 3+ gel film. After drying in a 100 °C environment for 1 hour, the film is annealed;

[0015] (4) Use a thermal evaporation device to evaporate an Al electrode on the back of the n + -Si substrate, and perform an alloying treatment at 400 °C in an N 2 atmosphere;

[0016] (5) Using magnetron sputtering, under DC conditions with a power of 80 W, a ZnO thin film layer with a thickness of 50 - 70 nm is sputtered on the surface of the TiO 2 :Er 3+ film;

[0017] (6) Using magnetron sputtering, under DC conditions with a power of 70 W, a circular ITO electrode with a thickness of 250 - 270 nm and a diameter of 1.5 mm is sputtered on the surface of the TiO 2 :Er 3+ film covered with a mask to form an n + -Si / TiO 2 :Er 3+ / ITO-structured electroluminescent device. A circular ITO electrode with a thickness of 250 - 270 nm and a diameter of 1.5 mm is sputtered on the surface of the ZnO layer covered with a mask to form an n + -Si / TiO 2 :Er 3+ / ZnO / ITO-structured electroluminescent device.

[0018] Preferably, in step (1), Er 3+ ions are doped into the TiO 2 gel, and Er 3+The concentration of the ions is 0.5 mol% - 5 mol%; the annealing conditions in step (3) are an annealing temperature of 800 °C, an annealing atmosphere of air, and an annealing time of 1 hour.

[0019] An electroluminescence method for an electroluminescent device based on a TiO 2 :Er 3+ luminescent layer: The ITO electrode is connected to the positive pole of the power supply, and the Al electrode is connected to the negative pole of the power supply (forward bias), and a voltage of 5 - 7 V is applied.

[0020] The beneficial effects obtained by the present invention are as follows:

[0021] (1) Using this method (sol - gel method) to prepare TiO 2 :Er 3+ luminescent layer is simple in technology, convenient to regulate the concentration of Er 3+ ions, low in cost, and convenient for production and promotion.

[0022] (2) Using this method, adding a ZnO layer as an electron blocking layer and a protective layer on the TiO 2 :Er 3+ luminescent layer realizes a significant improvement in the electroluminescence performance related to Er 3+ ions. Description of the Drawings

[0023] Figure 1 is a schematic diagram of the manufacturing process of the present invention.

[0024] Figure 2 is the X - ray (XRD) diffraction pattern of the TiO 2 :1mol% Er 3+ thin film, and the TiO 2 :1mol% Er 3+ thin film is in anatase phase structure.

[0025] Figure 3 is the electroluminescence spectrum of the n + -Si / TiO 2 :xmol% Er 3+ / ITO structure (x = 0.5 - 5) electroluminescent device under forward bias.

[0026] Figure 4 is the electroluminescence spectrum of the n + -Si / TiO 2 :1mol% Er 3+ / ITO device under different biases.

[0027] Figure 5 is the electroluminescence spectrum of the n + -Si / TiO 2 :1mol% Er3+ Cross-sectional view of an electroluminescent device with a / ZnO / ITO structure, TiO 2 : 1 mol% Er 3+ The thickness of the light-emitting layer is about 75 nm, the thickness of the ZnO layer is about 55 nm, and the thickness of the ITO transparent electrode is about 226 nm.

[0028] Figure 6 is n + -Si / TiO 2 : 1 mol% Er 3+ / ITO device and n + -Si / TiO 2 : 1 mol% Er 3+ Electroluminescence spectra of the / ZnO / ITO device at 6 V. Specific embodiments

[0029] The following is a more detailed description of the specific embodiments of the present invention through the description of examples, in order to help those skilled in the art have a more complete, accurate and in-depth understanding of the inventive concept and technical solution of the present invention.

[0030] Example 1: Preparation method of an electroluminescent device based on TiO 2 :Er 3+ First, anhydrous ethanol, tetrabutyl titanate, acetylacetone, deionized water and Er(NO 3 ) 3 ·5H 2 O are fully dissolved and mixed, and an appropriate amount of nitric acid is added to adjust the pH≈2. Then, it is placed in a 60°C water bath environment and continuously stirred for 4 hours, and cooled and left standing for 1 week to form a uniform TiO 2 :Er 3+ gel. An appropriate amount of the gel is measured and drop-coated onto a cleaned n + -Si substrate, and the rotation speed of the spin coater is set to 5000 revolutions per minute, and the film is spin-coated for 60 s to form a uniform TiO 2 :Er 3+ gel film. After drying in an environment of 100°C for 1 hour, the film is annealed in an air atmosphere at 800°C for 1 hour. Finally, an Al electrode is evaporated on the back of the n + -Si substrate by thermal evaporation, and a ZnO layer and an ITO transparent electrode are sputtered by magnetron sputtering to form an electroluminescent device. Specifically, it includes the following steps:

[0031] (1) Anhydrous ethanol, tetrabutyl titanate, acetylacetone, and deionized water are mixed evenly according to a volume ratio of 20:7:3:1, and a little nitric acid is added to adjust the pH≈2. According to the molar concentration ratio of Ti:Er = 99.5 mol%:0.5 mol%, Er(NO 3) 3 ·5H 2 O and fully dissolve it into the precursor solution. Then, place the mixed solution in a 60°C water bath environment and continuously stir for 4 hours. After cooling and standing for 1 week, a uniform TiO 2 :Er 3+ gel is formed for standby.

[0032] (2) Use the RCA standard cleaning process to clean the silicon wafer squares cut into 1×1 cm 2 thoroughly.

[0033] (3) Measure 30 μl of the prepared TiO 2 :Er 3+ gel and drop-coat it onto the cleaned n + -Si substrate. Set the rotation speed of the spin coater to 5000 revolutions per minute and spin-coat for 60 s to form a uniform TiO 2 :Er 3+ gel film. After drying in a 100°C environment for 1 hour, anneal the film in an 800°C air atmosphere for 1 hour.

[0034] (4) Use a thermal evaporation device to evaporate an Al electrode on the back of the n + -Si substrate, and perform an alloying treatment at 400°C in an N 2 atmosphere to form an ohmic contact with a resistivity of approximately 0.001 Ω·cm.

[0035] (5) Use magnetron sputtering under DC conditions with a power of 80 W to sputter a ZnO thin film layer with a thickness of 50 - 70 nm on the surface of the TiO 2 :Er 3+ film.

[0036] (6) Use magnetron sputtering under DC conditions with a power of 70 W to sputter a circular ITO electrode with a thickness of 250 - 270 nm and a diameter of 1.5 mm on the surface of the TiO 2 :Er 3+ film covered with a mask to form an n + -Si / TiO 2 :Er 3+ / ITO-structured electroluminescent device. Sputter a circular ITO electrode with a thickness of 250 - 270 nm and a diameter of 1.5 mm on the surface of the ZnO layer covered with a mask to form an n + -Si / TiO 2 :0.5 mol% Er 3+ / ZnO / ITO-structured electroluminescent device.

[0037] Example 2: The rest are the same as in Example 1, except that:

[0038] Weigh Er(NO 3 ) 3 ·5H 2 O precisely according to the molar concentration ratio of Ti:Er = 99 mol%:1 mol%, and fully dissolve it in a mixed solution of anhydrous ethanol, tetrabutyl titanate, acetylacetone, and deionized water (volume ratio: 20:7:3:1). Add a little nitric acid to adjust the pH ≈ 2. Place the mixed solution in a 60°C water bath environment and stir continuously for 4 hours. After cooling and standing for 1 week, a uniform TiO 2 :Er 3+ gel is formed. Measure 30 μl of the gel and drop-coat it onto a cleaned n + -Si substrate, and spin-coat at 5000 revolutions per minute for 60 s to form a uniform TiO 2 :Er 3+ gel film. After drying in a 100°C environment for 1 hour, anneal the film in an 800°C air atmosphere for 1 hour. Finally, evaporate Al electrodes on the back of the n + -Si substrate by thermal evaporation and perform alloying treatment at 400°C in an N 2 atmosphere. Sputter a circular ITO transparent electrode with a thickness of 250 - 270 nm and a diameter of 1.5 mm on the surface of the TiO 2 :Er 3+ film covered with a mask plate to form an n + -Si / TiO 2 :1 mol% Er 3+ / ITO-structured electroluminescent device.

[0039] Example 3: The rest are the same as in Example 1, except that:

[0040] Weigh Er(NO 3 ) 3 ·5H 2 O precisely according to the molar concentration ratio of Ti:Er = 98 mol%:2 mol%, and fully dissolve it in a mixed solution of anhydrous ethanol, tetrabutyl titanate, acetylacetone, and deionized water (volume ratio: 20:7:3:1). Add a little nitric acid to adjust the pH ≈ 2. Place the mixed solution in a 60°C water bath environment and stir continuously for 4 hours. After cooling and standing for 1 week, a uniform TiO 2 :Er 3+ gel is formed. Measure 30 μl of the gel and drop-coat it onto a cleaned n + -Si substrate, and spin-coat at 5000 revolutions per minute for 60 s to form a uniform TiO 2 :Er 3+ gel film. After drying in a 100°C environment for 1 hour, anneal the film in an 800°C air atmosphere for 1 hour. Finally, evaporate Al electrodes on the back of the n + -Si substrate by thermal evaporation and perform alloying treatment at 400°C in an N 2Alloying treatment was carried out at 400 °C in an atmosphere. A circular ITO transparent electrode with a thickness of 250 - 270 nm and a diameter of 1.5 mm was sputtered on the surface of the TiO 2 :Er 3+ thin film by magnetron sputtering, forming an n + -Si / TiO 2 :2 mol% Er 3+ / ITO-structured electroluminescent device.

[0041] Example 4: The rest are the same as in Example 1, except that:

[0042] According to the molar concentration ratio of Ti:Er = 95 mol%:5 mol%, Er(NO 3 ) 3 ·5H 2 O was accurately weighed and fully dissolved in a mixed solution of absolute ethanol, tetrabutyl titanate, acetylacetone, and deionized water (volume ratio: 20:7:3:1). A little nitric acid was added to adjust the pH ≈ 2. The mixed solution was placed in a 60 °C water bath environment and continuously stirred for 4 hours. After cooling and standing for 1 week, a uniform TiO 2 :Er 3+ gel was formed. 30 μl of the gel was measured and drop-coated onto a cleaned n + -Si substrate, and spin-coated at 5000 revolutions per minute for 60 s to form a uniform TiO 2 :Er 3+ gel thin film. After drying at 100 °C for 1 hour, the thin film was annealed in an air atmosphere at 800 °C for 1 hour. Finally, an Al electrode was evaporated on the back of the n + -Si substrate by thermal evaporation, and alloying treatment was carried out at 400 °C in an N 2 atmosphere. A circular ITO transparent electrode with a thickness of 250 - 270 nm and a diameter of 1.5 mm was sputtered on the surface of the TiO 2 :Er 3+ thin film by magnetron sputtering, forming an n + -Si / TiO 2 :5 mol% Er 3+ / ITO-structured electroluminescent device.

[0043] Figure 2 is the X-ray (XRD) diffraction pattern of the TiO 2 :1 mol% Er 3+ thin film. The XRD test results show that the TiO 2 :1 mol% Er 3+ thin film has a single anatase phase structure.

[0044] Figure 3 is for n + -Si / TiO2 : x mol% Er 3+ / ITO structures (x = 0.5, 1, 2, 5) electroluminescence spectra of the electroluminescent device under forward bias. When the Er 3+ ion concentration increases to 1 mol%, the corresponding electroluminescent device has the best electroluminescent performance, especially in the near-infrared electroluminescent performance. As the Er 3+ ion concentration further increases, due to the concentration quenching effect, the electroluminescent intensity of each band gradually weakens.

[0045] Figure 4 is n + -Si / TiO 2 : 1 mol% Er 3+ / ITO device electroluminescence spectra at different bias voltages. As the driving voltage increases, the electroluminescent intensity of the Er 3+ ions in the visible light band and the near-infrared light band gradually increases, which is due to more carriers being injected into the TiO 2 : 1 mol% Er 3+ luminescent layer.

[0046] Example 5: The rest is the same as in Example 2, except that:

[0047] Accurately weigh Er(NO 3 ) 3 ·5H 2 O according to the molar concentration ratio of Ti:Er = 99 mol%: 1 mol% and fully dissolve it in a mixed solution of anhydrous ethanol, tetrabutyl titanate, acetylacetone, and deionized water (volume ratio: 20:7:3:1). Add a little nitric acid to adjust the pH ≈ 2. Place the mixed solution in a 60 °C water bath environment and stir continuously for 4 hours. After cooling and standing for 1 week, a uniform TiO 2 :Er 3+ gel is formed. Measure 30 ul of the gel and drop-coat it onto a clean n + -Si substrate, and spin-coat at 5000 revolutions per minute for 60 s to form a uniform TiO 2 :Er 3+ gel film. After drying in a 100 °C environment for 1 hour, place the film in an 800 °C air atmosphere and anneal for 1 hour. Evaporate an Al electrode on the back of the n + -Si substrate by thermal evaporation and perform alloying treatment at 400 °C in an N 2 atmosphere. Use magnetron sputtering to sputter a ZnO thin film layer with a thickness of 50 - 70 nm on the surface of the TiO 2 :Er 3+ film, and finally sputter a circular ITO electrode with a thickness of 250 - 270 nm and a diameter of 1.5 mm on the surface of the ZnO layer covered with a mask plate to form an n +-Si / TiO 2 : 1 mol% Er 3+ / ZnO / ITO structured electroluminescent device.

[0048] Figure 5 is n + -Si / TiO 2 : 1 mol% Er 3+ / ZnO / ITO cross-sectional view of the structured electroluminescent device, TiO 2 : 1 mol% Er 3+ The thickness of the light-emitting layer is about 75 nm, the thickness of the ZnO layer is about 55 nm, and the thickness of the ITO transparent electrode is about 226 nm.

[0049] Figure 6 is n + -Si / TiO 2 : 1 mol% Er 3+ / ITO device and n + -Si / TiO 2 : 1 mol% Er 3+ / ZnO / ITO device electroluminescence spectra under 6V conditions. At a 6V driving voltage, the visible and near-infrared electroluminescence integrated intensities of the Er 3+ ions in the device with the ZnO layer are 4.4 times and 3.3 times that of the device without the ZnO layer, respectively. The ZnO layer, as an electron blocking layer and a protective layer, effectively improves the electroluminescent performance of the device.

[0050] The above embodiments are only to illustrate the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution according to the technical idea proposed by the present invention fall within the protection scope of the present invention; technologies not involved in the present invention can be realized through existing technologies.

Claims

1. An electroluminescent device based on a TiO 2 :Er 3+ luminescent layer, which structurally includes an aluminum electrode, an n + -Si substrate, a TiO 2 :Er 3+ luminescent layer, a ZnO layer, and an ITO transparent electrode layer in sequence. It is characterized in that The TiO 2 :Er 3+ luminescent layer is prepared by the sol-gel method, and the magnetron sputtered ZnO layer serves as an electron blocking layer and a protective layer; The TiO prepared by the sol-gel method 2 :Er 3+ The thickness of the light-emitting layer is 60-90 nm; TiO 2 :Er 3+ The concentration of Er 3+ ions in the light-emitting layer is 1 mol%.

2. An electroluminescent device based on a light-emitting layer of TiO 2 :Er 3+ as claimed in claim 1 It is characterized in that: The Si substrate is a single-sided polished heavily doped n + -Si substrate with a resistivity of 0.001 Ω·cm.

3. An electroluminescent device based on a light-emitting layer of TiO 2 :Er 3+ as claimed in claim 1 It is characterized in that: The thickness of the ZnO layer is 50 - 70 nm; the thickness of the ITO layer is 250 - 270 nm.

4. A method for preparing an electroluminescent device according to any one of claims 1 - 3, It is characterized in that comprising the following steps: (1) Absolute ethanol, tetrabutyl titanate, acetylacetone, and deionized water are mixed evenly in a volume ratio of 20:7:3:

1. A little nitric acid is added to adjust the pH to approximately 2. According to Ti:Er = (100 - x)mol%:xmol%, where x = 1, Er(NO 3 ) 3 ·5H 2 O is accurately weighed and fully dissolved in the precursor solution. Then, the mixed solution is placed in a 60°C water bath environment and continuously stirred for 4 hours. After cooling and standing for 1 week, a uniform TiO 2 :Er 3+ gel is formed for standby; (2) Cleaning the cut silicon wafer squares cleanly using the RCA standard cleaning process; (3) Measure 30 μl of the TiO prepared in step (1). 2 :Er 3+ gel, and drop-coat it onto a cleaned n + -Si wafer. Set the rotation speed of the spin coater to 5000 revolutions per minute and spin coat for 60 s to form a uniform TiO 2 :Er 3+ gel film. After drying the film in an environment of 100 °C for 1 hour, anneal the film. (4) Use a thermal evaporation equipment to evaporate an Al electrode on the back of the n + -Si substrate, and perform an alloying treatment under the condition of 400 °C in an N2 atmosphere; (5) Using magnetron sputtering, a ZnO thin film layer with a thickness of 50 - 70 nm is sputtered on the surface of the TiO 2 :Er 3+ thin film; (6) By using magnetron sputtering, a circular ITO electrode with a thickness of 250 - 270 nm and a diameter of 1.5 mm is sputtered on the surface of the TiO 2 :Er 3+ thin film to form an electroluminescent device with an n + -Si / TiO 2 :Er 3+ / ITO structure. A circular ITO electrode with a thickness of 250 - 270 nm and a diameter of 1.5 mm is sputtered on the surface of the ZnO layer covered with a mask plate to form an electroluminescent device with an n + -Si / TiO 2 :Er 3+ / ZnO / ITO structure.

5. The method for preparing an electroluminescent device according to claim 4, It is characterized in that In the step (1), Er 3+ ion-doped TiO 2 The concentration of Er 3+ ions in the gel is 1 mol%; the annealing conditions in the step (3) are an annealing temperature of 800 °C, an annealing atmosphere of air atmosphere, and an annealing time of 1 hour.

6. The method for preparing an electroluminescent device according to claim 5, It is characterized in that In step (5), magnetron sputtering is carried out by DC sputtering method with a sputtering power of 80 W, and in step (6), magnetron sputtering is carried out by DC sputtering method with a sputtering power of 70 W.

7. A light emitting method of an electroluminescent device based on a TiO 2 :Er 3+ light emitting layer, It is characterized in that The ITO electrode is connected to the positive pole of the power supply, the Al electrode is connected to the negative pole of the power supply (forward bias), and a voltage of 5 - 7 V is applied.

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