CN100508243C - OLED devices that emit red light - Google Patents

Abstract

The invention discloses a red light-emitting OLED device, which comprises a substrate, an anode, a hole injection layer placed on the anode, a hole transport layer placed on the hole injection layer, and a light emitting layer placed on the hole transport layer. Red light layer, electron transport layer placed on the red light emitting layer, electron injection layer placed on the electron transport layer, cathode layer placed on the electron injection layer, between the hole transport layer and the light emitting layer or/ An embedding layer for improving luminous efficiency is arranged between the luminescent layer and the electron transport layer. This structure embeds a layer on top of the original structure, so it doesn't conflict with other structures or practices. After embedding, the spectrum of the device does not change, and the efficiency has been significantly improved.

Description

OLED devices that emit red light

technical field

The invention relates to an organic electroluminescence display device OLED, in particular to a red light-emitting OLED device.

Background technique

The structure of organic electroluminescent devices (that is, organic light emitting diode referred to as OLED) includes a substrate, an anode, and a cathode. Between the anode and the cathode are various functional organic/inorganic layers, including but not limited to hole injection layers (HIL), hole transport layer (HTL), light emitting layer (EML), electron transport layer (ETL), electron injection layer (EIL). In order to improve the efficiency, the structure of the light-emitting layer is often a host/guest doping system, that is, the organic light-emitting dye is doped into the organic light-emitting host by using the principle of energy transfer, so that the organic light-emitting dye is excited to emit light.

At present, the common method of emitting red light-emitting OLED devices is to adopt the method of double main body single doping, and the specific structure is: ITO/2TNATA: F4TCNQ (3%, 100nm)/NPB (20nm)/Alq3+rubrene: red dopant ( 2%, 50nm)/BPhen(20nm)/LiF(1nm)/Al(150nm). However, due to the limitation of materials, the luminous efficiency of red devices has not been greatly improved. At present, the efficiency of red devices can reach about 6CD/A.

purpose of invention

The object of the present invention is to provide a red OLED device capable of improving luminous efficiency.

The above object can be achieved through the following technical measures: a red light-emitting OLED device, comprising a substrate, an anode, a hole injection layer placed on the anode, a hole transport layer placed on the hole injection layer, The red light-emitting layer on the hole transport layer, the electron transport layer placed on the red light-emitting layer, the electron injection layer placed on the electron transport layer, and the cathode layer placed on the electron injection layer are characterized in that: An embedding layer for improving luminous efficiency is provided between the hole transport layer and the light emitting layer or/and between the light emitting layer and the electron transport layer.

The thickness of the embedding layer described in the present invention is between 0.01nm and 1nm.

The material used for the embedding layer in the present invention is rubrene or its derivatives.

The luminescent material of the luminescent layer in the present invention is a fluorescent material or a phosphorescent material.

This invention adds a very thin red fluorescent seven intercalation layer between the light emitting layer (EML) and the electron transport layer (ETL) or between the hole transport layer (HTL) and the light emitting layer (EML). This structure embeds a layer on top of the original structure, so it doesn't conflict with other structures or practices. In the case of other layer structures and thicknesses being exactly the same, compare the device effects of inserting or not inserting a thin layer of red fluorescent seven. Compared with the uninserted device, the efficiency of the inserted device has no change in the spectrum, and the efficiency has been significantly improved.

Comparing structures A (traditional device structure) and B (with thin red fluorescent seven embedded in the traditional structure), the efficiencies of A and B are 5.84CD/A and 7.33CD/, respectively. The efficiency of the B structure is increased by 1.49CD/A compared with the A structure, but the color of the device has not changed (A and B color coordinates are both 0.65, 0.34) (see Figure 2).

After such a change, from the current-voltage (Figure 3) and brightness-voltage (Figure 4) curves, the voltage of the structure B device is slightly increased, and the steepness is also slightly increased. However, its spectrum has not changed, but its brightness has increased significantly.

There are two reasons for this increase in efficiency:

1) The thin red fluorescent seven intercalation layer forms a hole trap center. During recombination, some excitons that should have escaped from the light-emitting layer are confined to the edge of the light-emitting layer, effectively blocking some excitons so that they Lighting at the edge causes it to be excited again at the edge to emit light;

能量传输，把能量转移到红色发光材料，使其发光。而且由于空穴捕捉中心的作用，对整个器件的平衡起到了有利作用，同时器件的寿命也得到了提高。2) The thin red fluorescent seven embedding layer itself emits light, through

Energy transfer, transferring energy to red luminescent material, making it glow. Moreover, due to the function of the hole capturing center, the balance of the whole device is played a favorable role, and the lifetime of the device is also improved at the same time.

Description of drawings

FIG. 1 is a schematic diagram of the overall structure of a red OLED device with a red fluorescent seven embedded thin layer.

Figure 2 is a comparison of the EL spectra of two device structures with and without a red fluorescent seven embedded thin layer.

Fig. 3 is a comparison of the voltage-current density curves of two device structures with red fluorescent seven embedded thin layer and without red fluorescent seven embedded thin layer.

Figure 4 is a comparison of the current-brightness curves of two device structures with red fluorescent seven embedded thin layer and without red fluorescent seven embedded thin layer.

Detailed ways

The production principle of small molecule organic light-emitting diodes is to deposit multi-layer functional layers and light-emitting layer films on a glass substrate by evaporation in a high vacuum chamber on a pre-evaporated ITO substrate. Here ITO is used as transparent anode. The fabrication steps of this light-emitting device are as follows:

(a) The cleaned ITO substrate 10 .

(b) The anode ITO 11 substrate was treated with O ₂ plasma.

(c) The sequence of coating organic film layers is: hole injection layer 12, hole transport layer 13, red fluorescent seven embedded thin layer 14, red light emitting layer 15, red fluorescent seven embedded thin layer 16, electron transport layer 17, Electron injection layer 18 . The above-mentioned embedding thin layers 14 and 16 may also be only one of them.

(d) The manufacturing method of the hole injection layer is to use two materials in the form of host and doping to form a P-type structure, so as to reduce the voltage of the device. The concentration of doping is controlled at 0.5%-10%. Evaporation rate and temperature are independently controlled for each evaporation source. The light emitting material of the red light emitting layer 15 is a fluorescent material or a phosphorescent material.

(e) When evaporating the embedded layer, use low rate control or temperature control, and the evaporation rate should be as small as possible, so that the uniformity of the film is better. The general rate is controlled at 0.001~0.5 , because the energy transfer efficiency of the red fluorescent seven intercalation is 100%, so the red fluorescent seven intercalation layer does not need to be too thick, and the thickness is set between 0.01nm and 1nm. The evaporation time is not long and will not affect the production beat. The material used for the embedding layer is red fluorescent seven or its derivatives. The other layers above are processed as usual.

(f) Cathode aluminum 19 is evaporated.

(g) Paste a desiccant on the back cover, and then dispense glue for packaging. The whole process is carried out in a pure N ₂ environment.

Embodiment 1 of the present invention made by the above steps: ITO/2TNATA: F4TCNQ (3%, 100nm)/NPB (20nm)/rubrene (0.01～1nm)/Alq3+rubrene: red dopant (2%, 50nm)/BPhen (20nm)/LiF(1nm)/Al(150nm)

Embodiment 2 of the present invention made by the above steps: ITO/2TNATA: F4TCNQ (3%, 100nm)/NPB (20nm)/Alq3+rubrene: red dopant (2%, 50nm)/rubrene (0.01～1nm)/BPhen (20nm)/LiF(1nm)/Al(150nm)

Embodiment 3 of the present invention obtained by the above steps: ITO/2TNATA: F4TCNQ (3%, 100nm)/NPB (20nm)/rubrene (0.01～1nm)/Alq3+rubrene: reddopant (2%, 50nm)/rubrene ( 0.01～1nm)/BPhen(20nm)/LiF(1nm)/Al(150nm).

The efficiency and voltage of the traditional structure are 5.84CD/A and 5.92V@50mA/cm2 respectively, while the efficiency and voltage of the first and second embodiments of the present invention can reach 7.33CD/A and ^{6.28V@50mA/cm2} respectively. The efficiency and voltage of Example 3 can reach 7.28CD/A and 6.97V respectively.

Claims (4)

1, a kind of OLED device that glows, comprise substrate, anode, place the hole injection layer on the anode, place the hole transmission layer on the hole injection layer, place the rubescent photosphere on the hole transmission layer, place the electron transfer layer on the rubescent photosphere, place the electron injecting layer on the electron transfer layer, place the cathode layer on the electron injecting layer, it is characterized in that: between described hole transmission layer and luminescent layer, be provided with the embeding layer that is used to improve luminous efficiency, perhaps be provided with the embeding layer that is used to improve luminous efficiency between luminescent layer and the electron transfer layer, perhaps simultaneously at luminescent layer and electron transfer layer, be provided with the embeding layer that is used to improve luminous efficiency between the hole transmission layer.

2, according to the described OLED device that glows of claim 1, it is characterized in that: described embeding layer thickness is between 0.01nm～1nm.

3, according to the described OLED device that glows of claim 1, it is characterized in that: the material that described embeding layer adopts is red glimmering seven.

4, according to the described OLED device that glows of claim 1, it is characterized in that: the luminescent material of described luminescent layer is fluorescent material or phosphor material.

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