DE10359881A1 - Organic light emitting diode (OLED) component e.g. for surface display, has current flow through OLED-component measured - Google Patents

Abstract

A method for controlling an OLED-component consisting of a first electrode (20 a light-emitting layer (3) and a second electrode (4)., in which the light emitting layer has both electro-luminescence properties and photoluminescence extinction/suppression properties. In a sensor mode for detection of a signal input at the OLED element, a voltage in the forward direction, which is smaller than the inception/threshold voltage (Ue) of the light-emitting layer (5), or a voltage in the backward direction is applied and the current flow through the OLED-component is measured and inferred from the time change of the current flow to a signal input. Independent claims are included for (1) (A) An OLED-component (2) (B) An active matrix-OLED display.

Description

The The invention relates to an OLED device and active matrix display based on OLED devices and a method of controlling the same with those in the preambles the claims 1, 8, 14 and 16 mentioned features.

flat panel displays based on organic light emitting diodes (OLEDs) are characterized high brilliance and wide viewing angle. As a self-adhesive Need technology OLED displays do not provide backlighting and can therefore operate in conditions with low to medium ambient light component energetically advantageous be used.

Under Conditions with a high level of ambient light, e.g. in direct Sunlight, but must be disproportionate a lot of power is spent to achieve the required brightness. moreover are the needed ones streams for the Control of the emissive components correspondingly high. Therefore are reflective and reemissive technologies at a high ambient light level, such as liquid crystal displays, superior. Their disadvantage, however, is that they are for the operation under conditions with low ambient light, need a backlight (backlight) through which are the structural dimensions and the energy consumption at low ambient light proportion disproportionately increase.

OLED devices that can be operated on the basis of organic light emitting diodes in both the emissive and in the reemissive mode, are out DE 100 42 974 A1 known. Such a photoluminescence display element (PQD, Photoluminescence Quenching Device) has the structure similar to an organic light emitting diode and can be operated in the self-emitting mode, ie without ambient light, but also in the reemissive mode. In the reemissive mode, the intensity of the photoluminescence light is increased by applying a voltage in the reverse direction; In emissive mode, the intensity of the electroluminescent light is controlled by applying a voltage in the forward direction. In this case, the application of a voltage in the forward direction means that both electrons (from the cathode) and holes (from the anode) are injected into the organic material via the two electrodes. In contrast, the PQD is polarized in the reemissive mode so that charges can not be injected but can be extracted. With an appropriate choice of contact and emitter materials can be with the components described above, the operation in both the emissive and in the reemissive (Photolumineszenzlöschungs-) mode, the so-called dual operation, realize. Advantageously, no backlight is required for this purpose. Prerequisite for the reemissive operation is that sufficient ambient light can be absorbed. In addition, it is necessary to provide both negative and positive control voltages for the display element.

In a device having electroluminescence and photoluminescence quenching behavior due to the internal photo effect, a photocurrent is generated. Incoming light (photons) create electron-hole pairs and lead to a photocurrent.

This Principle can be used to an OLED device or an OLED display as Photosensor e.g. to use in a scanner.

Of the current flowing through the OLED device (Photocurrent) hangs due to the internal photo effect of the intensity of the light starting with which the OLED component is illuminated. A higher lighting results in a higher one Photocurrent.

From a voltage which is less than the threshold voltage corresponds the component current almost the photocurrent.

The change of the photocurrent can be used as a signal, for example, for optical information (intensity of the ambient light of the Convert OLED device into electrical signals.

There are known touch screens in which the screen surface acts as an interface between the electrical device and the user. The touchscreen regularly includes a translucent substrate. This substrate may be rigid, for example, made of glass, but also of flexible material, such as plastic. Different layers arranged on the screen act as touch-sensitive elements of the touch screen. The touch-sensitive elements include, for example, transducers and electronic circuits necessary to detect contact by an object so that the exact position of the touch on the (touch) screen can be determined. Corresponding lines are connected to electronic circuits so that signals can be routed towards the touch screen or away from the touch screen. The cables are regularly connected to an external control unit. The external control unit routes the various signals to the touch screen and performs calculations based on the responses of the touch-sensitive elements upon touching, in order to (X, Y) coordinates of the touch to determine.

It are different touch screen technologies known.

systems, which the resistance change through the contact more transparent conductive Exploiting layers are called "resistive" systems such systems which register the capacitive changes by touching the screen surface, referred to as "capacitive" systems. In the aforementioned cases will be electrical or optical signals used to provide the user information (the pressing on the screen surface) to transform into electrical information. Here is the touch screen function (Detection of a signal input) from the screen function (illustration of information by converting electrical signal voltages into Light). For example, it works in the case of an LC display (LCD) with integrated touch screen function the LCD only in its screen function, e.g. the ad that information that appears after touching a button should be. The sensor element (touch screen function) becomes on the screen surface arranged as a separate device or separate function. One Field more transparent, more conductive Lines are used regularly for a corresponding touch to be able to detect.

EP 1282032 A2 (Seiko Epson) describes the combination of a screen and a touch screen (for mobile applications, PDO monitor applications), both of which are electrically interconnected using wireless communication via infrared or radio.

EP1248228, US20020171610 and US20020186208 (Eastman Kodak) describe a similar one Principle. An OLED display includes a transparent substrate with two sides. Light emitting elements of an electroluminescent display are arranged on one side of the substrate. Touch-sensitive elements a touchscreen are arranged on the other side of the substrate, according to the invention OLED and touch screen are arranged on one and the same substrate. A disadvantage of this is that display elements and touch-sensitive elements on different sides (of the substrate) are arranged, which is different Production technologies and steps required and accordingly leads to a considerable cost disadvantage.

The Combination of an OLED and a light sensor is in GB 2315594 (CDT). Here are light sensor and light emitter in the the same layer (layer) arranged adjacent. An OLED based on PPV materials is used as a light-emitting element. The material, which for The sensor element used is a semiconducting polymer. The invention further includes that the material for the light-emitting and the photosensitive element may be of the same type. Of the Disadvantage of this invention is that lichtaussendendes Element and photosensitive element need space on the display surface, because there are physically separate components. This will change the display resolution and thus the picture quality reduced. Furthermore, the resolution of the sensor is the same Causes also low.

The The object of the invention is an OLED device and a Display based on organic light emitting diodes (OLED) indicate which both a display function for displaying information as well a touch (Screen) function for detecting a signal input on the surface of the Have displays / OLED device and cheaper than the known devices can be produced according to the prior art.

Farther a method for controlling an OLED device and a OLED displays are indicated by which both a screen function for displaying information as well as a touch (screen) function can be realized for detecting a signal input.

These The object is achieved by the features in the characterizing part of claims 1 and 8 (method claim) as well as the claims 14 and 16 (claim) in conjunction with the features in Generic term.

Advantageous embodiments The invention are contained in the subclaims.

A particular advantage of the invention is that a touch screen function can be implemented particularly cost-effectively for OLED components and OLED displays. For this purpose, an OLED device having a light-emitting layer having both electroluminescent and photoluminescent-quenching properties is switched not only to an emissive mode for emitting light by a forward voltage greater than the threshold voltage of the light-emitting layer, but to detection a signal input, the OLED device according to the invention is switched to a sensory mode, wherein the OLED device, a voltage in the forward direction, which smaller than the threshold voltage of the light emit light the layer is applied or a voltage in the reverse direction and the current flow through the OLED device is measured and closed from the temporal change of the current flow to a signal input. According to the invention, the fact is exploited that the OLED components whose organic layer has both electroluminescent properties and photoluminescence properties in dual operation, that is to say, can be switched in emissive and in reemissive operation. If the OLED component is operated in the forward direction in emissive operation and the applied voltage is greater than the threshold voltage of the OLED component, then light is emitted due to electroluminescence. However, when a positive voltage (forward direction) lower than the threshold voltage is applied to the OLED device, a negative current flows in the presence of suitable (sufficient) ambient light due to the generation of a photocurrent. In this case, the component current changes as a function of the intensity of the external ambient light, as long as the spectrum of the ambient light at least partially covers the absorption spectrum of the organic material of the OLED component. The characteristic of the component runs here in the fourth quadrant. Furthermore, the OLED device can be operated when applying a negative voltage (in the reverse direction) in the so-called photoluminescent quenching mode (reemissive mode). At a constant (applied in the backward direction) supply voltage of the OLED device, the height of the component current also depends on the intensity of the ambient light. According to the invention, the dependence between the component current and the intensity of the ambient light (with sufficient ambient light component) in the reemissive mode (application of a voltage in the reverse direction) or in the mode in which a voltage is applied in the forward direction, which is smaller than the threshold voltage of the OLED device, is hereinafter referred to as mode b - be used to realize a touchscreen function or a touch device function such that the OLED device is at least partially operated either in the reemissive mode or in mode b and the current flowing through the OLED device (component current) is measured and from the change in the component current is closed to a signal input. In this case, the fact is exploited that touching the OLED component, for example by the finger of a user, leads to a change in the ambient light intensity. Accordingly, it can be concluded from such a change in the ambient light intensity to a signal input, that is, in this case to a touch of the OLED device. For this purpose, an inventive OLED device has means for measuring the current flowing through the OLED device. Such an OLED component can be, for example, a luminous light switch, which generates a signal for switching on or off of light when touched. However, the OLED component according to the invention can also be, for example, a pixel of an OLED display.

In a preferred embodiment is the OLED device alternately in the emissive mode to emit light as well in the sensory mode, that is in the reemissive mode or in the mode b for detecting a signal input connected.

Around switching between emissive mode (light emission) and sensory mode (detection of a signal input) so inconspicuous that it is imperceptible to an observer, will switch between emissive mode and sensory mode preferably made with a frequency greater than 30 Hz.

Analogous to the inventive method for Controlling an OLED component is the method according to the invention for controlling an OLED display consisting of a plurality of separately controllable OLED devices whose light-emitting layers have both electroluminescent properties as well as photoluminescent quenching properties, wherein the OLED devices in an emissive mode for the transmission of Light are switchable, characterized in that in a sensory Mode for detecting a signal input to at least one OLED component of the OLED display a voltage in the forward direction, which is smaller than the threshold voltage of the light-emitting layer of the OLED device, or a voltage in the reverse direction applied and then measured the current flow through the OLED device and from the temporal change of the current flow is closed to a signal input.

In a preferred embodiment It is envisaged that between emissive mode and sensory Mode with a frequency greater than 30 Hz is switched back and forth to the optically for one User does not deteriorate perceptible properties of the display.

In an alternative embodiment, it is provided not to switch all the pixels of the OLED display between emissive mode and sensory mode, but at the same time a part of the OLED components (pixels of the OLED display) in the emissive mode and another part of Pixels in the sensory mode, preferably in each Mo switched pixels are evenly distributed across the display.

to Realization of the method according to the invention has an inventive OLED display at least one inventive OLED device with at least one means for measuring the through the OLED device flowing Electricity on. According to the invention can Part of the pixels of the display for a screen function (light emission in emissive mode) and at the same time another part of the pixels for detecting a signal input (in sensory mode). This is so far advantageous in that the selection of those pixels, which in the Emissive mode to be switched, it is done so that all OLED devices a have almost the same operating time in emissive mode. To It is envisaged the operating time of each pixel in the emissive Mode to measure and save. This makes it possible according to the invention that all pixels of the screen over time the same Wear characteristics are subject as pixels in the emissive Mode of rapid aging phenomena as pixels in the sensory Mode have.

The The invention will be explained in more detail with reference to embodiments.

It demonstrate:

1 : a schematic, sectional view of an active matrix OLED display according to the invention with integrated touch screen function;

2 : the current-voltage characteristic of an OLED device with and without ambient light;

3 a schematic OLED display according to the invention, in a sectional view, wherein a part of the pixels in the emissive mode and another part of the pixels in the sensory mode is switched;

4 : a schematic representation of the operation of an OLED display according to the invention at high ambient light content;

5 : the schematic representation of the operation of an OLED display according to the invention at low ambient light content and

6 : An OLED component of an OLED display according to the invention in a schematic representation.

To fulfill the functions for an OLED active matrix display according to the invention are applied to a substrate 1 ( 1 ) an indium tin oxide layer structure 2 and an organic, light-emitting layer structure 3 applied, wherein the organic layer structure 3 has both electroluminescent and photoluminescent quenching properties. Most light-emitting polymers such as PPV (polyphenylene vinylene) or PFO (polyfluorene) exhibit these properties. On the organic layer structure 3 becomes a metal layer structure 4 arranged. In this case, the indium-tin oxide layer structure forms 2 In the emissive operation of the OLED display, the anode layer and the metal layer structure 4 in emissive operation, the cathode layer off. The metal layer structure 4 may for example be formed of a layer structure consisting of calcium and aluminum. Between the indium tin oxide layer structure 2 and the organic layer structure 3 is a (not shown here) hole transport layer consisting of PEDT-PSS (Polyethylendioxythiophen-polystyrene sulfonic acid) arranged. Furthermore, the display according to the invention for each of the pixels 9 and 10 an ammeter 11 on, by means of which by the respective pixel 9 respectively. 10 flowing electricity can be measured. However, the measurement of the current flowing through the pixels does not necessarily have to be by an ammeter 11 ; but can also be done by alternative devices and / or methods.

2 shows the current-voltage curve of an OLED pixel. In this case, the solid line represents the current-voltage curve without ambient light, the dashed line the current-voltage curve of an OLED pixel with a high ambient light component. In the first quadrant (I.), the OLED device (pixel) becomes forward operated. The indium tin oxide layer structure 2 In this case, as an anode, the metal layer structure 4 used as a cathode. If the applied voltage is greater than the threshold voltage U _{E of} the pixel (subarea a), the pixel is in the electroluminescent mode and emits light. This means U _a > U _E. In this case, the threshold voltage U _{E is} understood as the voltage at which an OLED begins to emit light. This means that minority carriers are injected into the OLED. Only then is recombination and thus light emission possible.

In the fourth quadrant (IV., Subarea b), the pixel operates at sufficient ambient light component according to the solar cell principle (dashed line). When a positive voltage, which is lower than the threshold voltage U _{E of} the OLED device, is applied (portion b), a negative current (in the reverse direction) in the case of the presence of a sufficient ambient light angle les generated (dashed line). This current varies as a function of the intensity of the ambient light, provided that the spectrum of the ambient light the absorption spectrum of the organic material 3 at least partially covering. This means 0 <U _b <U _E.

The application of a negative voltage leads to the reemissive operation of the pixel. This is in 2 schematically represented by the third quadrant (III., Subrange c) (voltages less than zero, U _c <0, that is, applying the voltage in the reverse direction). With a constant supply voltage at the pixel, the height of the component current again depends on the intensity of the ambient light. It follows from the above that, given sufficient ambient light intensity, the current flowing through the pixel in the sensory mode (voltages lower than the threshold voltage U _E ) depends on the intensity of the ambient light. Therefore, according to the invention, the ambient light conditions directly at the pixel can be deduced from the current flowing through the pixel on the intensity of the ambient light and from the temporal change of the current.

To deal with the in 1 The display shown to be able to realize both the representation of information and a screen touch function, the pixel element 8th in emissive mode, ie by means of an OLED supply source 14 with a voltage in the forward direction which is greater than the threshold voltage U _{E of} the pixel 8th is (corresponds to subarea a in 2 ), the pixel 9 in the mode b, that is, with a voltage in the forward direction, which is smaller than the threshold voltage U _{E of} the pixel 9 is (corresponds to section b in 2 ) and the pixel element 10 in the reemissive mode, that is to say with a voltage in the reverse direction (corresponds to subarea c in FIG 2 ) operated. This causes the pixel 8th Light ends, with the pixels 9 and 10 do not emit light. By measuring the through the pixels 9 and 10 flowing current by means of the ammeter 11 can, due to the above-described relationship (between the current flowing through a pixel and the ambient light component) on the ambient light component in the vicinity of the pixels 9 and 10 getting closed. In order to be able to realize a simultaneous screen function (display of information by emitting light) and a screen touch function (detection of a signal input), it is provided according to the invention that within a predetermined time interval some pixels (pixels 8th ) in emissive mode and other pixels (pixels 9 and 10 ) are switched in sensory mode. It can be provided both that in the emissive mode and in the sensory mode operated pixels are arranged side by side at the same time as well as all pixels are sequentially switched in both the emissive and in the sensory mode.

In the embodiment according to 1 For example, the thickness of the ITO layer 2 was 180 nm (20 ohms / square), and the thickness of the organic layer 3 was 70 nm (Covion Super Yellow). The metal layer 4 had a thickness of 450 nm (50 nm calcium, 400 nm aluminum). Between the indium tin oxide layer structure 2 and the organic layer structure 3 is a (not shown here) hole transport layer with a thickness of thickness 35 nm (Baytron P ^® ) arranged. The threshold voltage U _E was 2.0 V.

An example of a spatial separation of pixels operating in emissive and sensory modes is in FIG 3 shown schematically. The thousand-thousand pixels 6 (emissive operation) are used to display information by emitting light. The photosensitive areas 7 (Pixels in sensory mode) are used to detect a possible touch of a user on the display surface. The photosensitive pixels 7 can be operated either in the reemissive mode (subarea c) or in mode b (subarea b). In both cases, a change in the intensity of the ambient light leads to a change of the extinction current or photocurrent, ie to a change in the component current. This current is constantly measured and monitored at the external display ports.

6 shows the schematic representation of a suitable circuit for an active driver matrix with self-blocking p-channel thin-film polysilicon field effect transistors T1 and T2 and a storage capacitor 16 for the OLED device 15 , The current is supplied to the external supply connections by means of an ammeter 11 measured. During a sampling cycle, all display lines are activated one after the other to obtain information about the current display illumination. The measured current corresponds to the ambient light intensity in the vicinity of the individual pixels. To minimize interference, only rapid changes in current or light intensity can be registered to determine the position of a light blocker, such as a finger or a light source, such as a light pen. Through the interconnection of several circuits of the 6 with N rows and M columns results in a display matrix with N · M display elements. All supply voltage connections of a column are interconnected and with a current measurement option (ammeter 11 ) fitted. Through a continuous, repetitive fast scanning of all lines video information can be displayed on the screen as well as in the Sensor mode, the ambient light intensity near the individual pixels are detected.

4 shows an inventive display with integrated touch screen in the case of a high ambient light component. The pixel 8th is switched to electroluminescent mode and is used to display information. The pixels 9 and 10 are switched to sensory mode (mode b or reemissive mode). The photocurrent or the extinction current through the pixels 9 respectively. 10 decreases as the pixel area passes through an opaque element 5 how to cover a finger, for example. The light source is the ambient light 12 such as sunlight used. As a result, this mode is preferably used outdoors.

5 describes the same function with the difference that no ambient light 12 is available. The pixels 8th are switched in electroluminescent mode and are used to display information. Furthermore, these pixels function 8th as a light source. The pixels 9 and 10 are switched in the light-sensitive (sensory) mode. The extinction current or photocurrent increases as the pixel area passes through an opaque element 5 how to cover a finger, for example. The emitted light of the pixels 8th is at least partially reflected by the finger and on the photosensitive elements 9 and 10 directed.

Finally will a logic circuit or a combination of a logic circuit and a software used to change the measured current in the desired Function like the touch screen function transferred to. Preferably the measured current values are digitized and by means of a Data preparation unit evaluated. Preferably, the current flow within a time interval measured by 1 ms.

It is possible, too, that the display works in two modes. One mode is the display mode, in that all pixels display display information, e.g. Text or Images. In the second mode, the display operates in touch screen mode, in which all pixels work as photosensitive elements. Between both modes will be very fast (for example, with a frequency of 50 Hz) so that disturbing influence of the touch screen mode for the User is not visible. The maximum frequency for back and forth Switching is limited by the lifetime of the individual states, which lies in the nanosecond range. To a noticeable flicker of the images is inventively a frequency of greater than 30 Hz provided.

In a full color display, the blue pixel is preferably as light-emitting pixel, and the green or red pixel as photosensitive Pixel operated. For this it is necessary that the spectral sensitivity sensitivity of the sensory mode pixel is a large overlap having the spectrum of the emitting pixel.

Either the areas of the display that work as display elements as also the areas that work in the reemissive or mode b, can be set be or random determined or selected according to a scheme. The latter is preferable to counteract the effect of different ages of the pixels.

advantage of this invention is that touch screen function and screen function in a display using the same Pixel elements can be integrated. The different functions are only by selecting the Voltage at the pixel activated. As a result, the manufacturing processes comparable to those of conventional OLEDs, though an additional functionality added becomes. This means low manufacturing costs for a display with touch screen. This makes it possible new cost-effective To create applications, e.g. mobile devices without keypad.

Of Furthermore, it is known that the reverse operating voltage (during the Extinction mode) suppress the effect of different aging of the individual pixels or can reduce. Pixel, the stronger operate in emissive mode, aging faster, resulting in makes noticeable by display areas with lower brightness. Thereby, that in the present Invention light emitting and photosensitive (erasing pixels) pixels selected by software can, can the extinction mode priority for Pixel selected become stronger operated in emissive mode. As a result, the effect can be of different ages are reduced, resulting in better picture quality results.

1

active Matrix substrate

2

Indium tin oxide layer structure

3

organic layer

4

metal layer

5

light impermeable element

6

Lichtausendende Areas of a Invention

according to the display element (Pixel)

7

Photosensitive Areas of a Invention

according to the display element (Pixel)

8th

OLED Pixel element in electroluminescent mode (light emitting)

9

OLED Pixel element in mode b / sensor mode

10

OLED Pixel element in the extinction / sensor

mode

11

ammeter

12

Ambient light light

13

electroluminescent

14

OLED source

15

OLED display element

16

storage capacitor

T1

switching transistor

T2

switching transistor

V _DD

Supply voltage terminal

V _CATHODE

Cathode voltage connection

V _CELECT

Activation voltage connection

V _DATA

Data voltage connection

U _E

threshold voltage

a

applied voltage> U _E

b

U _E > applied voltage> 0

c

scale Voltage <0

Claims (16)

Method for controlling an OLED component consisting of a first electrode ( 2 ), a light-emitting layer ( 3 ) and a second electrode ( 4 ), wherein the light-emitting layer ( 3 ) has both electroluminescent and photoluminescent quenching properties, and in an emissive mode for emitting light to the OLED device, a forward voltage greater than the threshold voltage (U _E ) of the light-emitting layer (FIG. 3 ), characterized in that in a sensory mode for detecting a signal input to the OLED device, a voltage in the forward direction, which is smaller than the threshold voltage (U _E ) of the light-emitting layer ( 3 ), or a voltage is applied in the reverse direction and the current flow through the OLED device is measured and is concluded from the change over time of the current flow to a signal input. Method according to claim 1, characterized in that that the OLED device alternately in the emissive mode for the emission of light as well as in the sensory mode for the detection of a Signal input is switched. Method according to claim 1 or 2, characterized that switching between emissive mode and sensory Mode with a frequency greater than 30 Hz. Method according to one of the preceding claims, characterized characterized in that the measurement of the current flow through the OLED device within a predetermined time interval occurs. Method according to claim 4, characterized in that that the measurement of the current flow through the OLED device within a time interval of 1 ms takes place. Method according to one of the preceding claims, characterized characterized in that the current measured values are digitized. Method according to Claim 6, characterized that an assessment, whether due to the temporal change one digit of the digitized current readings Signal input to the OLED device is present, by means of a data processing device. Method for controlling an active-matrix OLED display comprising a multiplicity of separately controllable OLED components whose light-emitting layers ( 3 ) have both electroluminescent properties and photoluminescent quenching properties, wherein in an emissive mode for emitting light to individual OLED devices, a voltage in the forward direction, which is greater than the threshold voltage (U _E ) of the light-emitting layer, is applied, characterized in that in one Sensory mode for detecting a signal input to at least one OLED device of the active matrix OLED display a voltage in the forward direction, which is smaller than the threshold voltage (U _E ) of the light-emitting layer of the OLED device, or a voltage in the reverse direction is applied and the current flow through the OLED device is measured and is closed from the time change of the current flow to a signal input. Method according to claim 8, characterized in that that for detecting a signal input all OLED components of the active matrix OLED display alternately in the emissive mode as well as in the sensory mode be switched. Method according to claim 9, characterized in that that switching between emissive mode and sensory Mode with a frequency greater than 30 Hz. Method according to claim 8, characterized in that that at the same time a part of the OLED components of the active matrix OLED display in emissive mode and part of the OLED components of the active matrix OLED display be switched in the sensory mode, where in the respective Mode switched OLED devices are evenly distributed across the display. Method according to one of claims 8 or 11, characterized in that the operating time the individual OLED devices are measured and stored in emissive mode. Method according to claim 12, characterized in that that with a simultaneous operation of a part of the OLED components in the emissiven Mode and another part of the OLED devices in the sensory Mode, a selection of OLED devices such that all OLED devices have an almost equal operating time in emissive mode. OLED device consisting of a first electrode ( 2 ), a light-emitting layer ( 3 ) and a second electrode ( 4 ), wherein the light-emitting layer ( 3 ) has both electroluminescent and photoluminescent quenching characteristics, characterized by means for measuring the current flowing through the OLED device. An OLED device according to claim 14, characterized in that the means for measuring the current flowing through the OLED device comprises an ammeter ( 11 ). Active matrix OLED display consisting of a variety of OLED components according to one of Claims 14 and 15.