KR20110113553A - Characteristic measuring method of organic electro-luminescence device - Google Patents

Abstract

The present invention relates to an organic electroluminescent device, and more particularly, to a method for measuring the characteristics of an organic electroluminescent device providing a new means for evaluating the characteristics of the organic electroluminescent device.
It is a feature of the present invention to measure the capacitance of the organic electroluminescent diode before or after encapsulating the OLED.
The capacitance not only shows a very sensitive change in the thickness of the thin film, a change in the doping amount, and a change in the position of the light emitting layer, but also very sensitive to the change in the lifetime characteristics.
Therefore, it can be very useful for characterization of OLED devices as well as current-voltage characteristics measurement and lifetime measurement, and it is possible to reduce the process efficiency and cost of devices by properly using them during the manufacturing process.

Description

Characteristic measuring method of organic electroluminescence device

The present invention relates to an organic electroluminescent device, and more particularly, to a method for measuring the characteristics of an organic electroluminescent device providing a new means for evaluating the characteristics of the organic electroluminescent device.

Until recently, cathode ray tubes (CRT) have been mainly used as display devices. However, in recent years, flat panel such as plasma display panel (PDP), liquid crystal display device (LCD), organic electro-luminescence device (OLED), which can replace CRT Display devices are widely researched and used.

Among the flat panel display devices as described above, the organic light emitting display device (hereinafter referred to as OLED) is a self-light emitting device, and since the backlight used in the liquid crystal display device which is a non-light emitting device is not necessary, a light weight can be achieved.

In addition, the viewing angle and contrast ratio are superior to the liquid crystal display device, and it is advantageous in terms of power consumption. It is also possible to drive DC low voltage, has a fast response speed, and the internal components are solid, so it is strong against external shock and has a wide temperature range. It has advantages

In particular, since the manufacturing process is simple, there is an advantage that can reduce the production cost more than the conventional liquid crystal display device.

The OLED is a self-light emitting device that emits light through an organic light emitting diode, and the organic light emitting diode emits light through an organic light emitting phenomenon.

1 is a band diagram of an organic light emitting diode having a light emission principle due to a general organic light emitting phenomenon.

As shown, the organic light emitting diode 10 includes the anode and cathode electrodes 21 and 25 and a hole transport layer HTL 33 and an electron transport layer positioned therebetween. ETL) 35 and an emission material layer (EML) 40 interposed between the hole transport film 33 and the electron transport film 35.

In addition, a hole injection layer (HIL) 37 is interposed between the anode electrode 21 and the hole transport film 33 to improve the light emission efficiency, and the cathode electrode 25 and the electron transport film 35 are interposed therebetween. An electron injection layer (EIL) 39 is interposed therebetween.

In the organic light emitting diode 10, when positive and negative voltages are applied to the anode electrode 21 and the cathode electrode 25, the holes and cathodes of the anode electrode 21 are formed. The electrons are transported to the light emitting material film 40 to form excitons, and when such excitons transition from the excited state to the ground state, light is generated and emitted in the form of visible light by the light emitting material film 40.

On the other hand, the luminous efficiency and lifespan of the OLED are determined by the thickness and doping concentration of each organic light emitting layer 33, 35, 37, 39, 40, and is also affected by impregnation of impurities.

Impregnation of impurities may be mainly due to the organic material itself of the organic light emitting layers 33, 35, 37, 39, and 40, and in the process of forming the organic light emitting layers 33, 35, 37, 39, and 40, Will be affected.

In particular, the thickness of each of the organic light emitting layers 33, 35, 37, 39, 40 is very thin (1000 ~ 2000 GPa), if impurities are included in the deposition process can greatly affect the life of the actual OLED.

In addition, even in the process of depositing each organic light emitting layer (33, 35, 37, 39, 40), the thickness of each organic light emitting layer (33, 35, 37, 39, 40) can be slightly changed, using a plasma The surface treatment of the anode electrode 21 to be formed also changes little by little.

Even if the thicknesses of the organic light emitting layers 33, 35, 37, 39, and 40 are different, the efficiency and lifespan of the OLED are affected.

In particular, when there is foreign matter on the surface of the anode electrode 21, or when the surface roughness is large, it causes the leakage current (leakage current), thereby reducing the efficiency and life of the OLED. This becomes a bad factor of OLED.

Therefore, by measuring the accurate characteristics of the organic light emitting diode, it is necessary to provide an OLED with improved efficiency and lifespan and no defects. However, the measurement of the characteristics of the organic light emitting diode 10 is characterized by the luminance or chromaticity under certain driving conditions. It is only at the observation level of the phenomenon that measures change.

That is, the material change amount of the organic light emitting diode 10 may not be accurately measured, and thus, it may not be possible to diagnose what kind of defect has progressed.

Although the lifetime of the OLED can be measured accurately, it can be measured by driving the OLED for a long time. That is, the lifetime of the OLED is measured after encapsulation of the substrate on which the driving device (not shown) and the organic light emitting diode 10 are formed.

Therefore, it takes too much time to measure the lifetime of the OLED, even after the defective organic electroluminescent diode 10 is formed in the process of forming the organic light emitting diode 10, after the completion of the OLED encapsulation process Only when the defect is confirmed, it causes a problem of reducing the efficiency of the process and at the same time improving the process cost.

The present invention is to solve the above problems, it is a first object to immediately detect the failure of the organic light emitting diode in the process of forming the organic light emitting diode.

Through this, the second object is to provide an OLED that can accurately measure the characteristics of the OLED, thereby improving the reliability and quality of the screen.

In addition, the third object is to improve the efficiency of the process while reducing the process cost.

In order to achieve the above object, the present invention provides a method for measuring the characteristics of an organic light emitting diode comprising an array substrate, an organic light emitting diode comprising a first electrode, an organic light emitting layer, and a second electrode. Forming; The present invention provides a method for measuring characteristics of an organic light emitting diode, including measuring capacitance of the organic light emitting diode and comparing the capacitance with a reference value.

In this case, the reference value is ideal data of the measured capacitance, and is made through collection of data of a stable organic light emitting diode, and the reference value is defined as a graph showing the capacitance as a function of voltage.

In addition, the capacitance is determined whether the organic light emitting device is defective compared to the reference value, and through the capacitance, the position and thickness of each organic light emitting layer of the organic light emitting diode, or the doping amount of the dopant And it can be measured whether the failure according to the life of the organic light emitting device.

The measuring of the capacitance may be performed after the organic light emitting diode is formed on the array substrate or after the organic light emitting diode is completed. After measuring the capacitance, a failure turn is formed. Encapsulate.

The capacitance is measured by applying an AC signal having an amplitude of 1 mV to 5 V and a frequency of 100 Hz to 10 MHz to a voltage or a current within a range of -50 V to 50 V to the first electrode and the second electrode. The array substrate includes a transparent substrate defined by a plurality of pixel regions; Gate and data lines formed to cross one side and the other side of the pixel region; And a switching element and a driving element, each of the gate electrode, the semiconductor layer, the source and the drain electrode, and the first electrode being in contact with the drain electrode.

In addition, before the capacitance of the organic light emitting diode is measured, the organic light emitting diode is aged, and the aging is 0.1 mA / cm at the first electrode and the second electrode. Apply current of ² ~ 10A / cm ² and proceed for 10 seconds to 5 hours.

As described above, before or after encapsulating the OLED according to the present invention, by measuring the capacitance of the organic light emitting diode, there is an effect that can confirm the accurate light emission characteristics of the organic light emitting diode. Through this, there is an effect of determining whether the organic light emitting diode is defective or not.

In particular, even when impurities are included in the deposition process of each organic light emitting layer that is formed very thin, or even if the thickness of each organic light emitting layer is minutely changed, it is possible to measure even such a material change amount.

In addition, before the OLED is completed, it is possible to determine whether the organic light emitting diode is defective. Therefore, the efficiency of the process can be improved compared to the conventional method of determining the defect by measuring the characteristics of the OLED after encapsulating the OLED. There is an effect to reduce the.

1 is a band diagram of an organic light emitting diode having a light emitting principle due to a general organic light emitting phenomenon.
2 is a cross-sectional view schematically showing an OLED according to the present invention.
3 is a process flow diagram illustrating a manufacturing process of the OLED of FIG.
4A to 4C are cross-sectional views of organic light emitting diodes having different thicknesses of the organic light emitting layer.
FIG. 5A is a graph measuring current-voltage characteristics of the organic light emitting diodes of FIGS. 4A to 4C.
Figure 5b is a graph measuring the capacitance of the organic light emitting diode of Figures 4a to 4c.
6A through 6C are cross-sectional views of organic light emitting diodes having different positions of the light emitting material film.
FIG. 7A is a graph measuring current-voltage characteristics of the organic light emitting diodes of FIGS. 6A to 6C.
7B is a graph measuring capacitance of the organic light emitting diode of FIGS. 6A to 6C.
8A and 8B are graphs measuring current-voltage characteristics and capacitances according to the doping amount of a dopant in an organic light emitting diode.
9A and 9B are graphs measuring current-voltage characteristics and capacitances according to lifespans of organic light emitting diodes.
10 is a process flow diagram showing the manufacturing process of the OLED according to Example 5 step by step.
11A to 11B show the results of measuring luminance-lifetime and capacitance-voltage characteristics of an organic light emitting diode after an aging process.

Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings.

2 is a cross-sectional view schematically showing an OLED according to an embodiment of the present invention.

Prior to the description, the OLED 100 is divided into a top emission type and a bottom emission type according to the transmission direction of the emitted light. The bottom emission type has high stability and freedom of processing. Research on the bottom emission method is being actively conducted. Hereinafter, the OLED 100 of the present invention will be described as an example of a bottom emission method.

As illustrated, the OLED 100 according to the present invention includes a first substrate 101 having a driving and switching thin film transistor DTr (not shown) and an organic light emitting diode E, and a first substrate 101. Facing and consisting of a second substrate 102 for encapsulation, the first and second substrates 101, 102 are spaced apart from each other, the edge portion thereof is sealed through a seal pattern (120) and bonded together do.

In more detail, a switching thin film transistor (not shown) and a driving thin film transistor DTr are formed in each pixel region P on the first substrate 101. An organic light emitting layer 113 positioned on the first electrode 111 and the first electrode 111 connected to the thin film transistor DTr and emitting the light of a specific color, and an upper portion of the organic light emitting layer 113. An organic light emitting diode E consisting of the two electrodes 115 is formed.

The driving thin film transistor DTr includes a gate electrode 107, a semiconductor layer 103, and source and drain electrodes 110a and 110b. In this case, the driving thin film transistor DTr may be a top gate type including a polysilicon semiconductor layer, or may be formed as a bottom gate type made of pure silicon and impurities amorphous silicon.

Here, referring to the top gate type driving thin film transistor DTr as an example, the semiconductor layer 103 is made of polysilicon, and a central portion thereof has high concentrations on both sides of the active region 103a and the active region 103a. Source and drain regions 103b and 103c doped with impurities are formed, and a gate insulating film 105 is formed on the semiconductor layer 103.

The gate electrode 107 is formed on the gate insulating film 105 to correspond to the active region 103b of the semiconductor layer 103.

A first interlayer insulating film 109a is formed on the entire upper surface of the gate electrode 107, wherein the first interlayer insulating film 109a and the lower gate insulating film 105 are located on both sides of the active region 103a. And a semiconductor layer contact hole 116 exposing the drain regions 103b and 103c, respectively.

Next, the first interlayer insulating layer 109a including the semiconductor layer contact hole 116 is spaced apart from each other and contacts the source and drain regions 103b and 103c exposed through the semiconductor layer contact hole 116, respectively. Source and drain electrodes 110a and 110b are formed.

The second interlayer insulating film 109b is formed on the first interlayer insulating film 109a exposed between the source and drain electrodes 110a and 110b and the two electrodes 110a and 110b. And a drain contact hole 117 exposing the drain electrode 110b.

Although not shown in the drawing, the switching thin film transistor (not shown) has the same structure as the driving thin film transistor DTr and is connected to the driving thin film transistor DTr.

In addition, the first electrode 111 constituting the organic light emitting diode E, the organic light emitting layer 113, and the second electrode 115 are sequentially disposed in an area that substantially displays an image on the second interlayer insulating film 109b. It is formed.

The first and second electrodes 111 and 115 and the organic light emitting layer 113 formed therebetween form an organic light emitting diode (E).

Here, the first electrode 111 is formed for each pixel P, and a bank 119 is positioned in a non-pixel region (not shown) between the first electrodes 111 formed for each pixel P. .

That is, the bank 119 is formed in a matrix type having a lattice structure as a whole, and the first electrode 111 is separated by pixel region P with the bank 119 as a boundary portion for each pixel region P. FIG. It is formed into a structure.

The first electrode 111 is connected to the drain electrode 110b of the driving thin film transistor DTr through the drain contact hole 117 of the second interlayer insulating layer 109b.

In this case, the first electrode 111 serves as an anode electrode, and the second electrode 115 serves as a cathode electrode.

Accordingly, since the first electrode 111 is formed of a transparent electrode, and the second electrode 115 is formed of an opaque electrode, light emitted from the organic light emitting layer 113 is emitted toward the first electrode 111. Driven in a manner.

When a predetermined voltage is applied to the first electrode 111 and the second electrode 115 according to the selected color signal, the OLED 100 is injected into the hole and the second electrode 115 provided from the first electrode 111. The electrons are transported to the organic light emitting layer 113 to form an exciton, and when the exciton transitions from the excited state to the ground state, light is generated and emitted in the form of visible light.

At this time, since the emitted light passes through the transparent first electrode 111 to the outside, the OLED 100 implements an arbitrary image.

On the other hand, the organic light emitting diode E exhibits different light emission characteristics such as light emission luminance and chromaticity depending on the characteristics of the material constituting the device and the structure of the device.

That is, the organic light emitting diode E may have different device characteristics according to the surface state of each electrode 111 and 115, exposure by foreign matter, each thickness and position of the organic light emitting layer 113, or the doping amount of the dopant. Will have

The light emitting characteristics of the organic light emitting diode E also affect the efficiency and lifespan of the OLED 100, which becomes a defect factor of the OLED 100.

Accordingly, the OLED 100 of the present invention measures the capacitance of the organic light emitting diode E, thereby exhibiting light emission characteristics of the organic light emitting diode E due to a slight thickness change, a change in the doping amount, and impregnation with foreign matter. It can be measured accurately.

Through this, it may be determined whether the OLED 100 is defective.

In particular, since the organic light emitting diode (E) is formed and whether the organic light emitting diode (E) is defective can also be determined, the efficiency of the process can be improved and the process cost can be reduced.

This will be described in more detail with reference to FIG. 3.

FIG. 3 is a process flowchart illustrating a manufacturing process of the OLED of FIG. 2 step by step.

First, in a first step st1, a switching and driving thin film transistor (DTr of FIG. 2) is formed on a first substrate (101 in FIG. 2), that is, on the first substrate (101 in FIG. 2). A switching and driving thin film transistor (not shown) consisting of a gate electrode (107 in FIG. 2), a gate insulating film (105 in FIG. 2), a semiconductor layer (103 in FIG. 2), and source and drain electrodes (110a and 110b in FIG. , DTr) in FIG. 2.

In more detail, the amorphous silicon layer (not shown) is formed by depositing amorphous silicon in each pixel region (P of FIG. 2) of the first substrate (101 in FIG. 2), and irradiating a laser beam thereto or The heat treatment is performed to crystallize the amorphous silicon layer into a polysilicon layer (not shown).

Subsequently, a polysilicon layer (not shown) is patterned by performing a mask process to form a semiconductor layer (103 in FIG. 2) in a pure polysilicon state. In this case, before forming the amorphous silicon layer (not shown), an inorganic insulating material such as silicon oxide (SiO 2) or silicon nitride (SiN x) is deposited on the insulating substrate (101 in FIG. 2) to form a buffer layer (not shown). It may be.

Next, silicon oxide (SiO 2) is deposited on the pure polysilicon layer (103 in FIG. 2) to form a gate insulating film (105 in FIG. 2).

Subsequently, one of low-resistance metal materials such as aluminum (Al), aluminum alloy (AlNd), copper (Cu), and copper alloy is deposited on the gate insulating layer 105 of FIG. 2 to form a first metal layer (not shown). Subsequently, a mask process is performed to form a gate electrode 107 of FIG. 2 corresponding to the center portion of the semiconductor layer 103 of FIG. 2.

Next, using the gate electrode 107 of FIG. 2 as a blocking mask, a dopant, i.e., a trivalent element or a pentavalent element, is doped on the entire surface of the first substrate (101 in FIG. The source and drain regions (103b and 103c of FIG. 2) doped with impurities are formed in a portion outside the electrode (107 of FIG. 2), and the portion corresponding to the gate electrode (107 of FIG. 2) that is doped is pure. An active region (103a of FIG. 2) of polysilicon is formed.

Next, an inorganic insulating material such as silicon nitride (SiNx) or silicon oxide (SiO 2) is deposited on the entire surface of the first substrate (101 of FIG. 2) to form a first interlayer insulating film (109a of FIG. 2) on the entire surface, and a mask process The source and drain regions (103b and 103c of FIG. 2) of the semiconductor layer (103 of FIG. 2) are formed by simultaneously or collectively patterning the first interlayer insulating film (109a of FIG. 2) and the gate insulating film (105 of FIG. 2) below. The semiconductor layer contact holes 116 of FIG.

Subsequently, one of metal materials such as aluminum (Al), aluminum alloy (AlNd), copper (Cu), copper alloy, chromium (Cr), and molybdenum (Mo) is deposited on the first interlayer insulating film 109a of FIG. 2. To form a second metal layer (not shown), and patterning by performing a mask process to contact the source and drain regions 103b and 103c of FIG. 2 through the semiconductor layer contact hole 116 of FIG. (110a, 110b in Fig. 2) is formed.

In this case, the semiconductor layer (103 in FIG. 2), the gate insulating film (105 in FIG. 2), the gate electrode (107 in FIG. 2) and the first interlayer insulating film (109a in FIG. 2) are spaced apart from each other. 110a and 110b form a driving thin film transistor DTr.

Next, an organic insulating material such as photo acryl or benzocyclobutene (BCB) is coated on a first substrate (101 in FIG. 2) on which source and drain electrodes (110a and 110b in FIG. 2) are formed and a mask process is performed. By patterning through, a second interlayer insulating film (109b in FIG. 2) is formed.

In this case, the second interlayer insulating film 109b of FIG. 2 has a drain electrode contact hole 117 of FIG. 2 that exposes the drain electrode 110b of FIG. 2.

Next, in a second step st2, an organic light emitting diode (E in FIG. 2) is formed on a first substrate (101 in FIG. 2) on which a switching and driving thin film transistor (DTr in FIG. 2) is formed. The organic light emitting diode (E of FIG. 2) is formed by sequentially depositing a first electrode (111 of FIG. 2), an organic light emitting layer (113 of FIG. 2), and a second electrode (115 of FIG. 2).

In this case, the first electrode 111 of FIG. 2 contacts the drain electrode 110b of FIG. 2 through the drain contact hole 117 of FIG. 2 above the second interlayer insulating layer 109b of FIG. The upper part of 111 of FIG. 2 is coated with a photosensitive organic insulating material, for example, black resin, graphite powder, gravure ink, black spray, black enamel, and patterned to form a first electrode (111 of FIG. 2). ) To form a bank (119 in FIG. 2).

Next, an organic light emitting material is coated or deposited on the bank 119 of FIG. 2 to form an organic light emitting layer (113 of FIG. 2).

At this time, although not shown in the figure, the organic light emitting layer (113 of FIG. 2) may be composed of a single layer made of a light emitting material, in order to increase the luminous efficiency (hole injection layer), a hole transport layer (hole transport layer), It may be composed of multiple layers of a light emitting material layer, an electron transport layer, and an electron injection layer.

Next, an organic electroluminescent diode is formed by forming a second electrode (115 of FIG. 2) having a thick transparent conductive material deposited on the metal film on which the metal material having a low work function is deposited on the organic light emitting layer (113 of FIG. 2). (E of FIG. 2) is completed.

Thereby, the 1st board | substrate (101 of FIG. 2) of OLED (100 of FIG. 2) is completed.

Next, in a third step st3, after the failure turn (120 in FIG. 2) is formed at the edge of the first substrate (101 in FIG. 2) in which the organic light emitting diode (E in FIG. 2) is formed, By pressing the first substrate 101 (FIG. 2) and the second substrate 102 (FIG. 2) in close contact with each other, the first substrate 101 (FIG. 2) and the second substrate 102 (FIG. 2) are pressed. Make sure that they are fully mated to form the panel.

Through this, the OLED of the present invention (100 in FIG. 2) is encapsulated.

Next, in the fifth step (st5), the OLED panels forming the bonded panel state are cut for each unit pattern, which is a plurality of large mother substrates in order to increase productivity in manufacturing the OLED (100 in FIG. 2). After the unit cell is formed, each cell is separated into a single cell, which is a cutting process.

Through this, an organic field consisting of a switching and driving thin film transistor (DTr of FIG. 2), a first electrode (111 of FIG. 2), an organic light emitting layer (113 of FIG. 2), and a second electrode (115 of FIG. 2) The OLED (100 in FIG. 2) with the light emitting diode (E in FIG. 2) is completed.

At this time, the OLED of the present invention (100 in FIG. 2) is before or after the third step (st3), that is, before or after the formation of a failure turn (120 in FIG. 2) on the first substrate (101 in FIG. 2). The method further includes measuring the capacitance (st6) of the organic light emitting diode (E of FIG. 2).

Here, since the light emission luminance of the organic light emitting diode (E of FIG. 2) is directly controlled by the driving voltage or the current, the relationship between the driving voltage, the current, and the light emission luminance of the device is the basis for defining the characteristics of the device, Using this relationship, the device is driven by applying a specific voltage or current to achieve a desired light emission luminance.

The organic light emitting diode (E of FIG. 2) is made of a laminated structure of materials having different electronic characteristics, and the driving characteristics are changed according to a constant voltage or a constant current and frequency.

That is, even if the same organic electroluminescent diode (E in FIG. 2) is driven at the same voltage, the shape of the current signal applied by the difference in capacitance is greatly different.

Therefore, by measuring the capacitance of the organic light emitting diode (E of FIG. 2), it is possible to confirm the accurate light emission characteristics of the organic light emitting diode (E of FIG. 2). Through this, it is possible to determine whether the OLED (100 in FIG. 2) is defective according to the organic light emitting diode (E in FIG. 2).

In particular, the capacitance is very sensitive to the characteristic change, even when the organic material contains very fine impurities, foreign matter on the surface of each electrode (111, 113 of FIG. 2), or the surface roughness is large.

Therefore, even when impurities are included in the deposition process of each organic light emitting layer (113 of FIG. 2) which is formed very thin, or the thickness of each organic light emitting layer (113 of FIG. 2) is slightly changed, the capacitance is measured up to this material change amount. You can check through.

In particular, the capacitance is formed by the first and second electrodes (111 and 115 of FIG. 2) and the organic light emitting layer (113 of FIG. 2) of the organic light emitting diode (E of FIG. 2). Measurement can be performed at any time as long as conditions permit the charge to be applied to 111 and 115 of FIG. 2.

That is, the capacitance can be measured even inside the vacuum chamber in which the second electrode 115 is deposited, or at any time before or after the failure turn 120 is formed.

Therefore, it is possible to determine whether the organic light emitting diode (E in FIG. 2) is defective before the OLED (100 in FIG. 2) is completed. Therefore, the OLED (100 in FIG. 2) after encapsulating the OLED (100 in FIG. 2). The efficiency of the process can be improved and the process cost can be reduced compared to the conventional method of determining defects by measuring the characteristics of

Here, the process of determining whether the OLED (100 in FIG. 2) is defective by measuring capacitance is described in detail. First and second electrodes (111, in FIG. 2) of the organic light emitting diode (E) of FIG. The capacitance can be measured by applying an AC signal having a predetermined amplitude and frequency to a predetermined voltage (bias voltage) for driving the organic light emitting diode (E) of FIG. 2. Can be shown as a function of applied voltage.

In this case, the measured capacitance provides an average value with respect to time at each voltage of total charges accumulated in each layer of the organic light emitting layer (113 of FIG. 2).

Therefore, the capacitance is very sensitive to the thickness, doping amount, and the presence of impurities of each organic light emitting layer (113 in FIG. 2), thereby ensuring an ideal capacitance value of the OLED (100 in FIG. 2). Can be.

At this time, the ideal capacitance value is a value obtained by collecting data of the stable OLED (100 in FIG. 2) in the process of forming the organic light emitting diode (E of FIG. 2), and the respective values of the organic light emitting diode (E in FIG. 2). Change in capacitance according to the thickness change of the layers, change in capacitance according to the doping amount of the dopant of each light emitting material film of the organic light emitting diode (E of FIG. 2), and change in capacitance according to the planarization of the center and the edge of the substrate Along with information about the value, the lifetime and efficiency of the OLED (100 in Figure 2) is the ideal value, etc.

Therefore, it is possible to determine whether or not a defect according to the change of the characteristics of the OLED (100 in FIG. 2) by using the degree of deviation from the secured ideal capacitance value.

That is, during the fabrication process of the OLED (100 in FIG. 2), after the organic light emitting diode (E in FIG. 2) is formed, the first and second electrodes (111, in FIG. 2) of the organic light emitting diode (E in FIG. An alternating voltage or current signal having a predetermined frequency and amplitude is superimposed on the circuit 115, and the capacitance of the organic light emitting diode (E in FIG. 2) is obtained by measuring the voltage and current response signals. .

In this case, the capacitance of the present invention sets an arbitrary section within -50V to 50V between the first and second electrodes (111 and 115 in FIG. 2), using a frequency of 100 Hz to 10 MHz, and alternating current of 1 mV to 5 V. It is preferable to measure using a component.

The measured capacitance is plotted as a function of the applied voltage and compared to the graph curve of the ideal capacitance value, resulting in a failure of the organic light emitting diode (E in FIG. 2) through the deviation from the ideal capacitance curve. Determined by

In this case, since the capacitance of the switching or driving thin film transistor (DTr of FIG. 2) may be included in the measured capacitance value, the capacitance of the switching or driving thin film transistor (DTr of FIG. 2) is measured. It is also possible to later remove the capacitance value or measure the capacitance with a separate test organic electroluminescent diode (E in FIG. 2).

Example 1

Example 1 includes the first to third organic light emitting diodes having different thicknesses of the organic light emitting layer, as shown in FIGS. 4A to 4C, and measured their respective capacitances.

That is, as shown in FIG. 4A, the first organic light emitting diode has a thickness of the hole transport layer 113a between the first electrode 111 serving as the anode and the second electrode 115 serving as the cathode. 800 Å, the thickness of the light emitting material film 113c was 100 Å, and the thickness of the electron transport film 113b was 300 Å. As shown in FIG. 4B, the second organic light emitting diode may have a thickness of the hole transport film 113a. 750 Å, the thickness of the light emitting material film 113c was 200 Å, and the thickness of the electron transport film 113b was 250 3. As shown in FIG. 4C, the third organic light emitting diode may have a thickness of the hole transport film 113a. 700 Å, the thickness of the light emitting material film 113c was 300 Å, and the thickness of the electron transport film 113 b was 200 Å.

In this case, the first to third organic light emitting diodes first measured current-voltage characteristics as shown in FIG. 5A. As can be seen from the graph of FIG. 5A, the first to third organic electroluminescent diodes were measured. The current-density characteristics of the light emitting diodes have similar characteristics even when the thicknesses of the organic light emitting layers 113 are different.

Therefore, when the thickness of the organic light emitting layer 113 is formed differently, it can be seen that such a material change can not be confirmed through the measurement result of the current-density characteristics.

In other words, this means that there is a characteristic that is not confirmed by the change in current-density.

On the contrary, as a result of applying a voltage of a DC component of 0 to 5 V to the first and second electrodes 111 and 115, and measuring the capacitance by overlapping the frequency of 1 KHz and the amplitude of the AC component of 50 mV, FIG. As illustrated, when the capacitance-voltage characteristics of the first to third organic light emitting diodes having the respective organic light emitting layers 113 having different thicknesses are measured, the first to third organic light emitting diodes are measured. It can be seen that the capacitance of is measured differently.

As such, when the organic light emitting diode has a different thickness of each organic light emitting layer 113, the light emitting characteristics such as light emission luminance and chromaticity are different from each other, thereby affecting the efficiency and lifetime of the OLED (100 in FIG. 2). This is a failure factor of the OLED (100 in FIG. 2).

Thus, the present invention can be confirmed by measuring the capacitance that each of the thickness of the organic light emitting layer 113 of the organic light emitting diode is formed differently.

Therefore, if the amount of change in the thickness of each organic light emitting layer 113 is not intended or intended, but if the thickness of each organic light emitting layer 113 is changed, the organic light emitting diode based on the ideal capacitance curve through the capacitance measurement Can be determined to be defective.

[Example 2]

Example 2 includes the first to third organic electroluminescent diodes in which the light emitting material film in the organic light emitting diode in the organic electroluminescent diode is different from the first electrode as shown in FIGS. 6A to 6C, and the respective capacitances are measured. It was.

As shown in FIG. 6A, the first organic light emitting diode has a thickness of 600 Å between the first electrode 111 serving as the anode electrode and the second electrode 115 serving as the cathode electrode. The electron transport film 113b was formed to have a thickness of 300 mm, so that the light emitting material film 113c having a thickness of 300 mm was 600 mm away from the first electrode 111 and 300 mm away from the second electrode 115. It was formed to.

As shown in FIG. 6B, the second organic light emitting diode is formed to have the same thickness as that of the first organic light emitting diode, but the light emitting material film 113c is positioned 700 m away from the first electrode 111. The third organic electroluminescent diode is positioned so that the light emitting material film 113c is positioned 800 占 퐉 away from the first electrode 111, as shown in 6c. It was formed so as to be located 100 Å away from the second electrode (115).

7A and 7B show the results of measuring current-voltage characteristics and capacitance-current characteristics of the first to third organic light emitting diodes.

At this time, a voltage of a DC component of 0 to 5 V is applied to each of the first and second electrodes 111 and 115 of the first to third organic light emitting diodes, and the frequency of 1 KHz and the amplitude of the AC component of 50 mV are overlapped. The capacitance was measured.

Referring to the graph of FIG. 7A, it can be seen that the driving voltage of the first organic light emitting diode is large. However, the graph of FIG. 7B shows that the second organic electroluminescent diode has the largest capacitance.

This indicates that the thickness of the hole transport film 113a increases, so that the light emitting material film 113c is located farther from the first electrode 111, a higher voltage must be applied even when the same current is injected.

On the other hand, it can be seen that the capacitance of the first to third organic light emitting diodes is different depending on the amount of charge accumulated.

Therefore, when the amount of change in accordance with the distance between the light emitting material layer 113c is required from the first electrode 111, the organic light emitting diode can be determined to be defective based on the ideal capacitance curve through capacitance measurement.

Example 3

Example 3 shows the results of measuring the respective current-voltage characteristics and capacitance-voltage characteristics by varying the doping amount of the dopant of the light emitting material film in the organic light emitting diode. 8a and FIG. 8b.

Each of the organic light emitting diodes 1-A, 1-B, 1-C, and 1-D of FIGS. 8A and 8B has a first electrode serving as an anode electrode (111 of FIG. 6A) and a second serving as a cathode electrode. The thickness of the hole transport film (113a in FIG. 6A) and the electron transport film (113b in FIG. 6A) were formed to be 200 Å between the electrodes (115 in FIG. 6A), and the light emitting material film (113c in FIG. 6A) was formed. The thickness of was formed to 300 kPa.

In this case, 1-A is a state in which the dopant is not doped at all in the light emitting material film (113c of FIG. 6A), 1-B is a state in which 2% of the dopant is doped in the light emitting material film (113c in FIG. 6A), and 1 -C is doped with 4% dopant in the light emitting material film (113c of Figure 6a), 1-D is doped with 8% dopant in the light emitting material film (113c in Figure 6a).

Here, referring to FIG. 8A, it can be seen that current-voltage characteristics are measured such that all of the organic light emitting diodes 1-A, 1-B, 1-C, and 1-D have similar characteristics.

This indicates that the current-voltage characteristic is not easy to grasp the tendency even when the doping amount of the dopant of the organic light emitting diode is respectively doped differently.

In contrast, in the graph of FIG. 8B, as the doping amount of the dopant of the organic light emitting diode is increased, it can be seen that the capacitance value is larger and appears at a lower voltage.

As such, the capacitance has different light emission characteristics such as light emission luminance and chromaticity according to the doping amount of the dopant of each organic light emitting diode, thus affecting the efficiency and lifetime of the OLED (100 in FIG. 2). It becomes a failure factor of 100) of FIG.

Accordingly, the present invention can determine whether the organic light emitting diode is defective by measuring the capacitance of the organic light emitting diode according to the doping amount of the dopant.

Therefore, the capacitance measured according to the dopant amount of the dopant is compared based on the ideal capacitance curve, whereby the organic light emitting diode can be determined to be defective.

Example 4

Example 4 shows the results of measuring the current-voltage characteristics and the capacitance-current characteristics of the organic light emitting diodes according to the lifespan of FIGS. 9A and 9B.

The organic electroluminescent diodes of 2-A, 2-B, 2-C, and 2-D shown in FIGS. 9A and 9B each serve as a first electrode (111 in FIG. 6A) and a cathode as the anode electrode. The thickness of the hole transport film (113a in FIG. 6A) is 700 kPa and the thickness of the electron transport film (113b in FIG. 6A) is 200 kPa between the second electrode (115 in FIG. 6A). A thickness of 113c) was formed at 300 mm 3. The light emitting material film (113c of FIG. 6A) was formed by doping with 4% dopant.

Each of the 2-A, 2-B, 2-C, and 2-D organic light emitting diodes was sequentially deposited in a high vacuum environment, and as a result, the 2-A organic light emitting diode was 20% at the initial luminance. It took 3.4 hours to reduce the brightness, and 11.9 hours for the 2-B organic light emitting diode.

In addition, the 2-C organic light emitting diode took 17.8 hours, and the 2-D organic light emitting diode took 74.6 hours until the luminance decrease of 20% occurred at the initial luminance.

In this case, as can be seen from the graph of FIG. 9A, the current-voltage characteristics of each organic light emitting diode do not have much difference, but from the graph of FIG. 9B, the better the life of the organic light emitting diode is 3V. As the ratio of the capacitance values in the and 3.2V regions, that is, C (3V) / C (3 / 2V) is close to 1, the capacitance value is large around 2.5V.

As a result of measuring the capacitance of the organic light emitting diode, when the capacitance value is large around 2.5V as in the 2-D organic light emitting diode of FIG. 9B, the lifetime of the organic light emitting diode is separately measured. Even if it is not, it can be seen that the life of the organic light emitting diode is good.

Example 5

In Example 5, the aging process is performed before the capacitance measurement of the present invention.

Through this, the change in capacitance can be confirmed more clearly.

FIG. 10 is a flowchart illustrating a manufacturing process of an OLED according to Example 5 step by step, and the same reference numerals are given to the same parts that play the same role as the above-described description of FIG. 3 to avoid overlapping descriptions. In the fifth embodiment, only the characteristic contents described above will be described.

First, a switching and driving thin film transistor (DTr, not shown in FIG. 2) is formed on a first substrate (101 in FIG. 2) in a first step (st1), and in a second step (st2), a switching and driving thin film is formed. An organic light emitting diode (E of FIG. 2) is formed on a first substrate (101 of FIG. 2) on which a transistor (not shown, DTr of FIG. 2) is formed. An electrode (111 in FIG. 2), an organic light emitting layer (113 in FIG. 2), and a second electrode (115 in FIG. 2) are sequentially formed.

Next, in a third step st3, after the failure turn (120 in FIG. 2) is formed at the edge of the first substrate (101 in FIG. 2) in which the organic light emitting diode (E in FIG. 2) is formed, By pressing the first substrate 101 (FIG. 2) and the second substrate 102 (FIG. 2) in close contact with each other, the first substrate 101 (FIG. 2) and the second substrate 102 (FIG. 2) are pressed. Make sure that they are fully mated to form the panel.

Through this, the OLED of the present invention (100 in FIG. 2) is encapsulated.

Next, in the fifth step (st5), the OLED panels forming the bonded panel state are cut for each unit pattern, which is a plurality of large mother substrates in order to increase productivity in manufacturing the OLED (100 in FIG. 2). After the unit cell is formed, each cell is separated into a single cell, which is a cutting process.

Through this, an organic field consisting of a switching and driving thin film transistor (DTr of FIG. 2), a first electrode (111 of FIG. 2), an organic light emitting layer (113 of FIG. 2), and a second electrode (115 of FIG. 2) The OLED (100 in FIG. 2) with the light emitting diode (E in FIG. 2) is completed.

At this time, the OLED of the present invention (100 in FIG. 2) is before or after the third step (st3), that is, before or after the formation of a failure turn (120 in FIG. 2) on the first substrate (101 in FIG. 2). After the aging step (st6) of applying a constant alternating current or direct current to the organic light emitting diode (E of FIG. 2), a capacitance measurement step (st7) of the organic light emitting diode (E) of FIG. It further comprises a).

Here, the organic light emitting diode (E of FIG. 2) is made of a laminated structure of materials having different electronic characteristics, and the driving characteristics are changed according to a constant voltage or a constant current and frequency.

That is, even if the same organic electroluminescent diode (E in FIG. 2) is driven at the same voltage, the shape of the current signal applied by the difference in capacitance is greatly different.

Therefore, by measuring the capacitance of the organic light emitting diode (E of FIG. 2), it is possible to confirm the accurate light emission characteristics of the organic light emitting diode (E of FIG. 2). Through this, it is possible to determine whether the OLED (100 in FIG. 2) is defective according to the organic light emitting diode (E in FIG. 2).

At this time, the fifth embodiment of the present invention further performs an aging step st6 of applying a constant current to the organic light emitting diode (E of FIG. 2) for a predetermined time before measuring the capacitance, thereby preventing the blackout at the time of measuring the capacitance. The difference in dose can be seen more clearly.

Here, the process of determining whether the OLED (100 in FIG. 2) is defective by measuring capacitance is described in detail. First and second electrodes (111, in FIG. 2) of the organic light emitting diode (E) of FIG. A predetermined current is applied to 115, and the aging step st6 is performed by leaving the organic light emitting diode (E in FIG. 2) for a predetermined time while operating.

At this time, in the aging process st6 of the present invention, it is preferable to apply a current of 0.1 mA / cm ² to 10 A / cm ² , and it is preferable to proceed for about 10 seconds to 5 hours.

 After the aging step st6 is completed, a constant voltage for driving the organic light emitting diode (E in FIG. 2) to the first and second electrodes (111 and 115 in FIG. 2) of the organic light emitting diode (E in FIG. 2). The capacitance is measured by superimposing and applying an AC signal having a predetermined amplitude and frequency to (bias voltage).

The capacitance thus measured can be shown as a function of the applied voltage.

In this case, the measured capacitance provides an average value with respect to time at each voltage of total charges accumulated in each layer of the organic light emitting layer (113 of FIG. 2).

Therefore, the capacitance is very sensitive to the thickness, doping amount, and the presence of impurities of each organic light emitting layer (113 in FIG. 2), thereby ensuring an ideal capacitance value of the OLED (100 in FIG. 2). Can be.

At this time, the ideal capacitance value is a value obtained by collecting data of the stable OLED (100 in FIG. 2) in the process of forming the organic light emitting diode (E of FIG. 2), and the respective values of the organic light emitting diode (E in FIG. 2). Change in capacitance according to the thickness change of the layers, change in capacitance according to the doping amount of the dopant of each light emitting material film of the organic light emitting diode (E of FIG. 2), and change in capacitance according to the planarization of the center and the edge of the substrate Along with information about the value, the lifetime and efficiency of the OLED (100 in Figure 2) is the ideal value, etc.

Therefore, it is possible to determine whether or not a defect according to the change of the characteristics of the OLED (100 in FIG. 2) by using the degree of deviation from the secured ideal capacitance value.

That is, during the fabrication process of the OLED (100 in FIG. 2), after the organic light emitting diode (E in FIG. 2) is formed, the first and second electrodes (111, in FIG. 2) of the organic light emitting diode (E in FIG. An alternating voltage or current signal having a predetermined frequency and amplitude is superimposed on the circuit 115, and the capacitance of the organic light emitting diode (E in FIG. 2) is obtained by measuring the voltage and current response signals. .

In this case, the capacitance of the present invention sets an arbitrary section within -50V to 50V between the first and second electrodes (111 and 115 in FIG. 2), using a frequency of 100 Hz to 10 MHz, and alternating current of 1 mV to 5 V. It is preferable to measure using a component.

The measured capacitance is plotted as a function of the applied voltage and compared to the graph curve of the ideal capacitance value, resulting in a failure of the organic light emitting diode (E in FIG. 2) through the deviation from the ideal capacitance curve. Determined by

In this case, since the capacitance of the switching or driving thin film transistor (DTr of FIG. 2) may be included in the measured capacitance value, the capacitance of the switching or driving thin film transistor (DTr of FIG. 2) is measured. It is also possible to later remove the capacitance value or measure the capacitance with a separate test organic electroluminescent diode (E in FIG. 2).

In particular, in Example 5, since the aging step st6 is performed before the capacitance measurement, the change in the measured capacitance is very large.

11A to 11B illustrate the results of measuring luminance-lifetime and capacitance-voltage characteristics of an organic light emitting diode after an aging process.

Each of the organic light emitting diodes 3-A, 3-B, 3-C, and 3-D shown in FIGS. 11A and 11B may serve as a cathode and a cathode as shown in FIG. 6A. Hole injection film (not shown), hole transport film (113a in FIG. 6A), light emitting material film (113c in FIG. 6A), electron transport film (113b in FIG. 6A) and electrons between the second electrode (115 in FIG. 6A) An injection film (not shown) was formed under the same process conditions.

Each of the 3-A, 3-B, 3-C, and 3-D organic light emitting diodes was measured under the same process conditions, but the luminance-lifetime characteristics were measured. Referring to FIG. As can be seen, each of the organic light emitting diodes can be confirmed that the lifetime is measured differently at the same brightness.

That is, the 3-D organic light emitting diode took 0.6 hours to achieve a 2% reduction in luminance at the initial luminance, and the 3-C organic light emitting diode took 0.55 hours.

The 3-B organic electroluminescent diode took 0.45 hours, and the 3-A organic electroluminescent diode took 0.38 hours until a 2% reduction in luminance occurred at the initial luminance.

At this time, looking at the graph of Figure 11b, it can be seen that there is no difference in the capacitance (capacitance)-current (voltage) characteristics of each organic light emitting diode.

However, after the aging process is performed by applying a current of 450 mA / cm ² to each of the organic light emitting diodes of 3-A, 3-B, 3-C, and 3-D for 1 hour, the capacitance-capacitance- As a result of measuring the voltage characteristic, as shown in FIG. 11B, the capacitance of each of the organic light emitting diodes of each of 3-A ', 3-B', 3-C ', and 3-D' It can be seen that the voltage-current characteristic is measured differently.

In other words, by performing an aging process before measuring the capacitance-voltage characteristics of each organic light emitting diode, it is possible to measure the capacitance of the organic light emitting diode more clearly.

In addition, life and efficiency may be improved by stabilizing the organic light emitting diode through an aging process.

That is, the organic light emitting diode has a disadvantage in that the deterioration occurs as the usage time increases. In order to prevent such deterioration, a predetermined current is applied to each electrode of the organic light emitting diode and left for a predetermined time while operating to stabilize the operation of the organic light emitting diode, thereby improving the lifetime and efficiency of the organic light emitting diode. It can be.

As can be seen from the above embodiment, the capacitance shows a very sensitive change in the thickness change, the doping amount, and the change in the position of the light emitting layer, and it is also very sensitive to the change in lifetime characteristics. Can be.

Therefore, it can be very useful for characterization of OLED devices as well as current-voltage characteristics measurement and lifetime measurement, and it is possible to reduce the process efficiency and cost of devices by properly using them during the manufacturing process.

In particular, by performing the aging process of the organic light emitting diode before measuring the capacitance, it is possible to more clearly measure the change in capacitance.

The present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention.

st1: driving and switching thin film transistor formation
st2: Formation of organic light emitting diode
st3: fail turn
st4: encapsulation
st5: cutting
st6: capacitance measurement

Claims (11)

In the method for measuring the characteristics of an organic light emitting device comprising an array substrate, an organic light emitting diode comprising a first electrode, an organic light emitting layer and a second electrode,
Forming the organic light emitting diode;
And measuring a capacitance of the organic light emitting diode and comparing the capacitance with a reference value.
The method of claim 1,
The reference value is an ideal data of the measured capacitance, characterized in that the characteristic of the organic light emitting device is made through the collection of data of the stable organic light emitting device.
The method of claim 2,
Wherein the reference value is defined by a graph showing the capacitance as a function of voltage.
The method of claim 3, wherein
The capacitance is a characteristic measuring method of the organic light emitting device to determine whether the organic light emitting device is defective compared to the reference value.
The method of claim 4, wherein
Measurement of the characteristics of the organic light emitting diode, which can measure the location and thickness of each organic light emitting layer of the organic light emitting diode, the amount of dopants doped, and whether or not the failure according to the lifetime of the organic light emitting diode through the capacitance. Way.
The method of claim 1,
The measuring of the capacitance may be performed after the organic light emitting diode is formed on the array substrate or after the organic light emitting diode is completed.
The method according to claim 6,
Measuring the capacitance, and then forming and encapsulating a failure turn.
The method of claim 1,
The capacitance is measured by applying an AC signal having an amplitude of 1 mV to 5 V and a frequency of 100 Hz to 10 MHz to the first electrode and the second electrode within a range of -50 V to 50 V. How to measure the characteristics of.
The method of claim 1,
The array substrate
A transparent substrate defined by a plurality of pixel regions;
Gate and data lines formed to cross one side and the other side of the pixel region;
A switching element and a driving element, each of which is formed at an intersection point of the gate and data wiring, and comprises a gate electrode, a semiconductor layer, a source and a drain electrode, wherein the first electrode is in contact with the drain electrode. How to measure.
The method of claim 1,
The method of measuring the characteristics of the organic light emitting device for aging the organic light emitting diode before measuring the capacitance (capacitance) of the organic light emitting diode.
The method of claim 10,
The aging is a method of measuring the characteristics of the organic light emitting device to apply a current of 0.1mA / cm ² ~ 10A / cm ² to the first electrode and the second electrode, 10 seconds ~ 5 hours.

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