CN102222774A - Organic or inorganic electroluminescent device, anode of device and manufacturing method of anode - Google Patents

Abstract

The invention provides an organic or inorganic electroluminescent device, an anode of the device and a preparation method, belonging to the field of organic or inorganic electroluminescent devices. The present invention utilizes the metal and its silicide layer in parallel with the polysilicon layer to enhance the current conductivity, and proposes to use nano-thickness polysilicon and metal silicide composite film as the anode of the light-emitting device, thereby overcoming the strong absorption of visible light by the current common single crystal silicon anode, Nano-thickness polysilicon thin film is used as the anode when the square resistance is too large and other problems. The nano-thickness polysilicon and metal silicide composite anode of the present invention has the characteristics of good light transmission, good electrical conductivity, adjustable work function and hole injection, simple process, low cost and good stability. The anode material can not only be applied in the field of thin-film light-emitting devices such as organic light-emitting diode displays, but also may be applied in light detection and photovoltaic devices.

Description

Organic or inorganic electroluminescence device, device anode and preparation method

technical field

The invention relates to the field of organic or inorganic electroluminescence, in particular to an organic or inorganic thin-film optoelectronic device with nano-thick polysilicon and metal silicide composite thin film as a light-transmitting anode and a preparation method thereof.

Background technique

The current development of optoelectronic devices is very rapid, and organic electroluminescent devices have begun to enter commercial production. Electrode performance is very important for the role of optoelectronic devices. The electrodes on the light-emitting surface are required to have excellent light transmission and conductivity. The anode of organic electroluminescent devices also needs to adjust the resistivity of the electrodes to control the hole current to meet the balance of carrier injection. requirements to obtain high luminous efficiency. Currently commonly used ITO electrodes have good light transmittance and stability, but cannot control the hole injection current, the process is relatively complicated, and the finished product is also high. P-type single crystal silicon has many advantages as the anode of organic electroluminescence. The hole injection current can be controlled in a wide range by adjusting the resistivity of silicon. However, the anode substrate has a strong absorption of visible light, resulting in a decrease in luminous efficiency. Nanometer-thick polysilicon films can greatly reduce the strong absorption of visible light, but the sheet resistance is too large, generally much greater than 10 ⁴ Ω/□, resulting in increased series resistance and loss.

Contents of the invention

The object of the present invention is to provide an ultra-thin anode material for thin-film optoelectronic devices such as organic light-emitting diode displays, and a preparation method for the thin-film anode. The film anode of the invention has the characteristics of good electrical conductivity, low absorption in the visible light band, adjustable sheet resistance, stable chemical properties, simple process, low crystallization temperature, and low material and process costs.

Technical scheme of the present invention is as follows:

An anode of an organic or inorganic electroluminescent device, characterized in that: the anode is a composite material of polysilicon and metal silicide, and the thickness of the composite material is 5nm-100nm.

The composite material may contain trace amounts of metal elements.

An organic or inorganic electroluminescent device, comprising an anode, a light-emitting layer and a cathode, is characterized in that: the anode is a composite material of polysilicon and metal silicide, and the thickness of the composite material is 5nm-100nm.

The light-emitting layer of the device is a kind of polymer compound, metal complex, small molecule organic fluorescent compound or phosphorescent compound; the cathode uses aluminum, calcium, magnesium or other low work function metals, or these low work function metals and silver, other precious metals alloy.

Between the anode and the light emitting layer, add a hole transport layer; or between the cathode and the light emitting layer, add an electron transport layer; or between the anode and the light emitting layer, add a hole transport layer, between the cathode and the light emitting layer , to join the electron transport layer.

A method for preparing a composite anode material, the steps are as follows:

1) Deposit one or more layers of metal and P-type amorphous silicon sequentially on a transparent substrate; or deposit metal and P-type amorphous silicon as a layer, and the crystallization of P-type amorphous silicon by the metal have an inductive effect;

2) Under the condition of nitrogen protection at 400° C.-800° C., perform annealing-induced crystallization treatment for 5-300 minutes to form a composite material of P-type polysilicon and metal silicide.

The total thickness of the metal layer deposited in step 1) is 1nm-10nm, and the total thickness of the P-type amorphous silicon layer is 5nm-50nm.

The volume ratio of metal to P-type amorphous silicon in step 1) is from 1:100 to 75:100.

The metal includes but not limited to any one of Fe, Au, Ni, Al, Ti, Pt.

The deposition described in step 1) adopts physical vapor deposition including but not limited to any one in electron beam evaporation, magnetron sputtering, laser beam evaporation; or adopts chemical vapor deposition including but not limited to chemical vapor deposition, plasma enhanced chemical vapor deposition any of the deposits.

The above-mentioned polysilicon/metal silicide composite anode film layer used for thin-film optoelectronic devices in the visible light frequency band, considering the light transmittance and electrical conductivity, the total thickness is usually controlled at about 20nm.

The principle of the present invention is that the metal deposited on the transparent substrate combines with amorphous silicon under certain high temperature conditions to form a metal silicide, and as the dissolved silicon content in the metal increases to saturation, the silicon in the metal silicide will precipitate Crystallization forms polysilicon, and at the same time, amorphous silicon will continue to dissolve into the metal and then precipitate, so that the deposited amorphous silicon film is gradually transformed into a polysilicon film, and the polysilicon formed by crystallization undertakes the function of providing holes, injecting hole. At the same time, the metal silicide thin layer formed in the annealing crystallization can assist the current conduction of the electrode, and the current conduction enhancement effect is very obvious when the thickness of the thin film electrode is very thin, greatly reducing the voltage drop and loss of the electrode. The sheet resistance of a 20nm polysilicon electrode usually exceeds 10 ⁴ Ω/□, and the composite anode material can be much smaller than the resistivity of the polysilicon anode. Usually, the sheet resistance can be controlled below 1000Ω/□.

In the preparation of composite anode materials, most of the metals are transformed into metal silicides, and a small part of metal elements remain in the composite material. The content of metal elements in the composite anode does not exceed 10% of the overall composite anode material.

As shown in Figure 1, the preparation method of polysilicon and silicide composite anode is to sequentially deposit one or more layers of metal and P-type amorphous silicon on a transparent substrate; or deposit metal and P-type amorphous silicon as a layer , by selecting the induced metal, changing the composition ratio and thickness between metal and silicon, and adjusting the conditions of annealing and crystallization, the sheet resistance can be adjusted from 30Ω/□ to 10 ⁴ Ω/□.

For example, for a polysilicon/nickel silicide composite anode with a thickness of about 20nm, first deposit a 2nm nickel layer and a 20nm amorphous silicon layer. After annealing and crystallization, the thickness ratio of the P-type polysilicon layer to the nickel silicide layer in the anode is about It is 1:3, that is, the polysilicon layer is 5nm, the nickel-silicon compound is 15nm thick, and the sheet resistance is about 450Ω/□. Corresponding to the organic thin film light-emitting device shown in Figure 2, a specific example is used to illustrate that the specific structure (from bottom to top) is: Al/glass (substrate)/p-Si:Ni/NPB/CBP:(acac) ₂ Ir(ppy)/Bphen/Bphen:Cs ₂ CO ₃ /Sm/Au, the electroluminescence of its device can obtain the luminous efficiency up to 60lm/W. Fig. 3 shows the curve of brightness changing with voltage reflecting the luminous characteristics of its organic thin film light emitting device.

The polysilicon and silicide composite film anode has good light transmittance, especially in the infrared range, the light absorption of the anode is very small, which is beneficial to the light-emitting device to improve the light output efficiency, the visible light transmittance is close to 60%, and the infrared range light transmittance reaches 80%. The stable chemical and electrical properties of the composite anode can effectively protect the organic light-emitting device and prevent the degradation of organic materials due to oxidation, and it is also easy to deposit a reflective film on the transparent substrate on the electroluminescent device to improve the luminous efficiency of the above-mentioned light-emitting device. Or further processed to form a microcavity structure device. Therefore, polysilicon and silicide composite anode is a new type of electrode material with excellent performance, which has the main advantages of low light absorption, excellent stability, and low cost, as well as good electrical conductivity. Anode materials can not only be used in the field of thin-film light-emitting devices such as organic light-emitting diode displays, but also in light detection and photovoltaic devices.

Description of drawings

Figure 1 is a schematic diagram of three composite anode film deposition structures: 1(a) is a two-layer deposition structure, 1(b) is a multi-layer alternate deposition structure, and 1(c) is a single-layer co-deposition structure;

Figure 2 is a schematic structural view of an organic thin film light-emitting device using a nanometer-thick polysilicon/metal silicide anode;

Fig. 3 is a graph showing the luminous brightness of an organic thin film light-emitting device using a nanometer-thick polysilicon/metal silicide anode as a function of voltage variation;

Fig. 4 is the relation diagram of the sheet resistance of the polysilicon/nickel silicide composite anode and the thickness of the nickel layer and the crystallization temperature in the example 1;

Fig. 5 is the relationship figure of polysilicon/nickel silicide composite anode mobility and nickel layer thickness and crystallization temperature in example 1;

FIG. 6 is a graph showing the variation of visible light transmittance with nickel content in Example 2.

In Fig. 1, 1-transparent substrate, 2-amorphous silicon layer, 3-metal layer, 4-amorphous silicon and metal mixed layer.

Detailed ways

The present invention will be further described below in conjunction with the examples, but the present invention is not limited to the following examples.

Example 1: On a quartz transparent substrate, magnetron sputtering technology is used to deposit two layers of films respectively. The first layer uses a P-type silicon target to deposit a 20nm thick silicon film, and the second layer uses a nickel target to deposit thicknesses of 0.5 and 1 respectively. , 2, 4, 8, 12nm metal thin films. The purity of the deposited material is above 99.99%, the carrier concentration of the silicon material is from 10 ^-3 Ω·cm, and the background vacuum of the deposition vacuum chamber is better than 5×10 ^-5 Pa. The sample after depositing the film will undergo annealing-induced crystallization under the condition of nitrogen protection with a purity of 99.999%. The treatment temperature can be 540°C, 600°C or 800°C for 5 minutes. The finished product after annealing is a polysilicon/nickel silicide thin film, and its sheet resistance ranges from 8600Ω/□ to 30Ω/□. Figure 4 corresponds to the specific change curves of the sheet resistance of the polysilicon/nickel silicide composite anode under the conditions of different nickel deposition thicknesses and induced crystallization temperatures in this example, and a larger deposition metal layer thickness and a higher annealing temperature can reduce the composite The sheet resistance of the anode. Fig. 5 shows the change curve of carrier mobility of polysilicon/nickel silicide composite anode with different nickel deposition thickness and induced crystallization temperature. Increasing the annealing temperature can increase the carrier transport ability of the composite anode. However, with the increase of metal nickel content, the carrier mobility does not increase monotonously, and fluctuates due to the influence of polysilicon crystallization state, metal silicide content and metal element content in the composite anode.

Example 2: On transparent substrates such as glass, fused silica, and crystals, three layers of films were deposited using magnetron sputtering technology. The first and third layers were deposited with a P-type silicon target and both were silicon films with a thickness of 8-10nm. The second layer uses a nickel target to deposit a 1.5-3nm thick nickel metal film. The purity of the deposited material is above 99.99%, the carrier concentration of the silicon material is from 10 ^-3 Ω·cm, and the background vacuum of the deposition vacuum chamber is better than 5×10 ^-5 Pa. The sample after depositing the thin film will undergo annealing-induced crystallization under the condition of nitrogen protection with a purity of 99.999%, and the processing temperature is 540° C. for 5 minutes. The sheet resistance of the finished product after annealing is 450Ω/□, and the visible light transmittance is nearly 50%. Figure 6 shows that the visible light transmittance of the polysilicon/nickel silicide composite anode will decrease when only the nickel deposition thickness is increased. A higher nickel content has a great effect on the crystallization of amorphous silicon and the reduction of sheet resistance, but it also affects the light transmittance of the composite anode.

Example 3: On transparent substrates such as glass, fused silica, and crystal, two layers of thin films are deposited by electron beam evaporation. The first layer uses nickel or aluminum source to evaporate a metal film with a thickness of 1.5-3nm, and the second layer uses P-type silicon. Source evaporation deposition is 20nm thick amorphous silicon film. The purity of the deposited material is above 99.99%, the carrier concentration of the silicon material is from 10 ^-3 Ω·cm, and the background vacuum of the deposition vacuum chamber is better than 5×10 ^-4 Pa. The sample after depositing the film will undergo annealing-induced crystallization under the condition of nitrogen protection with a purity of 99.999%, and the treatment temperature is 540°C for 5 minutes to form a polysilicon/nickel silicide film or a polysilicon/aluminum silicide film.

Example 4: On transparent substrates such as glass, fused silica, and crystal, first thermally evaporate a layer of Al with a thickness of 8 nm, and then use plasma-enhanced CVD to deposit a layer of amorphous silicon film with a thickness of 20 nm. The reaction gas is silane, and high-purity Ar is used. Diluted with gas, the sample after depositing the film will be annealed to induce crystallization under the protection condition of high-purity nitrogen gas, the treatment temperature is 550°C, and the time is 10 minutes to form a polysilicon/aluminum silicide film.

In the above-mentioned embodiments of the present invention, the selected induction metal and the thickness and structure of the metal and amorphous silicon can be changed according to the injection carrier concentration and light transmittance requirements of the anode. For example, besides Ni and Al, the metal can also be Fe, Au, Ti, Pt.

In addition, the volume ratio of metal to P-type amorphous silicon is from 1:100 to 75:100.

In addition, under the condition of nitrogen protection at 400° C.-800° C., the annealing-induced crystallization treatment time may be 5-300 minutes.

The embodiments described above are not intended to limit the present invention. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention depends on the scope of the claims. defined.

Claims (10)

1. the anode of an organic or inorganic electroluminescent device, it is characterized in that: described anode is the composite material of polysilicon and metal silicide, this thickness of composite material is 5nm-100nm.

2. anode as claimed in claim 1 is characterized in that: described composite material contains metallic element.

3. an organic or inorganic electroluminescent device comprises anode, luminescent layer and negative electrode, it is characterized in that: described anode is the composite material of polysilicon and metal silicide, and the thickness of described composite material is 5nm-100nm.

4. device as claimed in claim 3 is characterized in that: described composite material contains metallic element.

5. as claim 3 or 4 described devices, it is characterized in that: the luminescent layer of described device is a kind of of macromolecular compound, metal complex, micromolecule organic fluorescent compounds or phosphorescent compound; Negative electrode adopts aluminium, calcium, magnesium or other low workfunction metal, or these low workfunction metal and alloy silver-colored, other noble metal.

6. one kind prepares the method for anode material according to claim 1, and its step is as follows:

1) plated metal and P type amorphous silicon each one or more layers successively on transparent substrates; Or be metal and P type amorphous silicon mixed deposit one deck, the crystallization of described metal pair P type amorphous silicon has induction;

2) under 400 ℃ of-800 ℃ of nitrogen protection conditions, carry out the annealing induced crystallization and handled 5-300 minute, form P type polysilicon and metal silicide composite material.

7. method as claimed in claim 6 is characterized in that: the metal level gross thickness that deposits described in the step 1) is 1nm-10nm, and P type amorphous silicon layer gross thickness is 5nm-50nm.

8. as claim 6 or 7 described methods, it is characterized in that: the volume ratio of metal described in the step 1) and P type amorphous silicon was from 1: 100 to 75: 100.

9. method as claimed in claim 6 is characterized in that: described metal includes but not limited to any one among Fe, Au, Ni, Al, Ti, the Pt.

10. method as claimed in claim 6 is characterized in that: the employing of deposition described in step 1) physical vapour deposition (PVD) includes but not limited to any one in electron beam evaporation, magnetron sputtering, the laser beam evaporation; Or the employing chemical vapour deposition (CVD) includes but not limited in chemical vapour deposition (CVD), the plasma reinforced chemical vapour deposition any one.

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