Optoelectronic component and method for operating an optoelectronic component

Abstract

The invention relates to an optoelectronic component, the optoelectronic component comprises a light-emitting layer stack, and an electrothermal protection element, which is connected to the layer stack in the component and has a temperature-dependent resistor.

Claims

1. An optoelectronic component comprising: a light-emitting layer stack including organic layers; and an electrothermal protection element connected to the layer stack, wherein the electrothermal protection element has a temperature-dependent resistance, wherein the electrothermal protection element includes a PTC thermistor switch and a NTC thermistor switch, wherein the PTC thermistor switch is connected in series with the layer stack, wherein the NTC thermistor switch is connected in parallel with the layer stack, and wherein the electrothermal protection element is configured to decrease or interrupt an emission of light at the light-emitting layer stack when a temperature of the light-emitting layer stack exceeds a threshold temperature T.sub.crit.

2. The optoelectronic component according to claim 1, wherein the electrothermal protection element and the light-emitting layer stack are commonly arranged on a substrate and covered by a common encapsulation.

3. The optoelectronic component according to claim 1, further comprising a heat-conducting element commonly arranged on a substrate between the layer stack and the electrothermal protection element.

4. The optoelectronic component according to claim 3, wherein the heat-conducting element is arranged on the substrate and in lateral direction between the electrothermal protection element and the light-emitting layer stack, and/or wherein the heat-conducting element is in direct mechanical contact with the light-emitting layer stack and the electrothermal protection element, and/or wherein the heat-conducting element comprises a metal.

5. The optoelectronic component according to claim 1, wherein the PTC thermistor switch is configured to decrease or interrupt a current flowing through the light-emitting layer stack during operation of the light-emitting layer stack when the threshold temperature T.sub.crit at the PTC thermistor switch is exceeded.

6. The optoelectronic component according to claim 1, wherein the NTC thermistor switch is configured to deflect a current flowing through the light-emitting layer stack during operation of the light-emitting layer stack via the NTC thermistor switch and to decrease the current at the layer stack when the threshold temperature T.sub.crit at the NTC thermistor switch is exceeded.

7. A method for operating an optoelectronic component according to claim 1, the method comprising: decreasing or interrupting, by the electrothermal protection element, the emission of light at the light-emitting layer stack when the temperature of the light-emitting layer stack exceeds the threshold temperature T.sub.crit.

8. The optoelectronic component according to claim 3, wherein the heat-conducting element is arranged on the substrate and in lateral direction between the electrothermal protection element and the light-emitting layer stack, wherein the heat-conducting element is in direct mechanical contact with the light-emitting layer stack and the electrothermal protection element, and wherein the heat-conducting element comprises a metal.

9. The optoelectronic component according to claim 3, wherein the heat-conducting element is arranged on the substrate and in lateral direction between the electrothermal protection element and the light-emitting layer stack, and wherein the heat-conducting element is in direct mechanical contact with the light-emitting layer stack and the electrothermal protection element.

10. The optoelectronic component according to claim 3, wherein the heat-conducting element is in direct mechanical contact with the light-emitting layer stack and the electrothermal protection element, and wherein the heat-conducting element comprises a metal.

11. The optoelectronic component according to claim 3, wherein the heat-conducting element is arranged on the substrate and in lateral direction between the electrothermal protection element and the light-emitting layer stack, and wherein the heat-conducting element comprises a metal.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further advantages, advantageous embodiments and developments result from the exemplary embodiment described in the following in conjunction with the figures.

(2) FIGS. 1A and 2A show a schematic top view of an optoelectronic component with an electrothermal protection element.

(3) FIGS. 1B and 2B show a typical curve of an electric resistance of the electrothermal protection element depending on the temperature.

(4) FIG. 3A shows a schematic side view of a layer stack having a switch layer.

(5) FIG. 3B shows an exemplary charge carrier transport of a thermo-material depending on the temperature.

(6) FIG. 3C shows a curve of a minimum voltage for operating a layer stack having a switch layer depending on the temperature.

(7) FIG. 4 shows an optoelectronic component according to an embodiment.

(8) In the exemplary embodiments and figures, similar or similarly acting constituent parts are provided with the same reference symbols. The elements illustrated in the figures and their size relationships among one another should not be regarded as true to scale, unless otherwise indicated. Rather, individual elements may be represented with an exaggerated size for the sake of better representability and/or for the sake of better understanding.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

(9) FIG. 1A schematically shows a top view of an optoelectronic component 10. A light-emitting layer stack 1 and an electrothermal protection element 3 are commonly arranged on a substrate 5 and internally connected on the substrate 5 by means of electrical conductor paths. The electrothermal protection element 3 of FIG. 1A advantageously is a PTC thermistor switch connected in series with the layer stack 1. The PTC thermistor switch can be applied on to the substrate 5 in a manner to be spaced laterally from the layer stack 1, for example.

(10) The substrate 5 furthermore has an anode contact 5a and a cathode contact 5b arranged thereon for external contacting, by means of which the PTC thermistor switch and the layer stack 1 are advantageously connected in series.

(11) Furthermore, a heat-conducting element 9 is commonly arranged on the substrate 5 together with the electrothermal protection element 3 and the layer stack 1. The heat-conducting element 9 is located between the layer stack 1 and the electrothermal protection element 3 here, and is in direct contact to both of them, such that the heat of the layer stack 1 can be transmitted to the PTC thermistor switch advantageously in a good manner.

(12) An encapsulation 8 (striped representation) covers the layer stack 1, the electrothermal protection element 3 and the substrate 5 and encapsulates the individual components to form an optoelectronic component 10.

(13) FIG. 1B shows a dependency of the electric resistance R of a PTC thermistor switch from the temperature T on the PTC thermistor switch for three different PTC thermistor switches R1, R2 and R3. The electric resistance of PTC thermistor switch R1 increases sharply from a critical temperature T.sub.crit of 40 C. The PCT thermistor switches R2 and R3 have their resistance increasing sharply at 60 C. and 120 C., respectively. Prior to the increase, the resistance remains largely constant with the increase in temperature.

(14) If a PTC thermistor switch having such a characteristic according to FIG. 1A is connected in series with a layer stack, advantageously an OLED, and if the voltage at the OLED is maintained constant, e.g., by means of an external voltage source, the current by means of which the layer stack is operated decreases. An OLED is automatically dimmed or turned-off thereby if the temperature exceeds a critical temperature T.sub.crit, above which the electrical resistance increases sharply.

(15) FIG. 2A schematically shows an optoelectronic component 10 similar to FIG. 1A in a top view. A light-emitting layer stack 1 and an electrothermal protection element 3 are commonly arranged on a substrate 5 and internally connected in the component 10 on the substrate 5 by means of electrical conductor paths, wherein, advantageously, the electrothermal protection element 3 in FIG. 2A is a NTC thermistor switch connected in parallel with the layer stack 1.

(16) A heat-conducting element 9 is arranged on the substrate 5 together with the electrothermal protection element 3 and the layer stack 1. The heat-conducting element 9 is located between the layer stack 1 and the NCT thermistor switch and is in direct contact to both of them, such that the heat of the layer stack 1 can be transmitted to the NCT thermistor switch advantageously in a good manner. An encapsulation 8 (striped representation) covers the NTC thermistor switch 3, the substrate 5 and the layer stack 1, which is advantageously formed as an OLED.

(17) FIG. 2B shows a dependency of the electric resistance R of an NTC thermistor switch from the temperature T at the NTC thermistor switch for two different NTC thermistor switches H1 and H2 in comparison to a copper wire K. As the temperature increases, the electric resistances of the NTC thermistor switches H1 and H2 asymptomatically approach a minimum value. In parallel connection with the layer stack, this results in a parallel current path to open, and the current at the layer stack 2 of FIG. 2A can be decreased.

(18) FIG. 3A shows a layer stack 1 including a switch layer 4 in a schematic side view. The layer stack 1 further includes a first contact 1B, a second contact 1c and, e.g., an emission unit 1d. The emission unit 1d can advantageously be configured as an active zone. In FIG. 3A, the layer stack 1 further includes an electron transport layer ET and a hole transport layer HT, with the emission unit 1d being arranged between the electron transport layer ET and the hole transport layer HT. The switch layer 4 can be the electron transport layer and/or the hole transport layer.

(19) FIG. 3B shows a change in the proportion of thermo-material, which changes its structure and thus the extent of charge carrier transport as the temperature T increases. Along with an increase in temperature, part of the material in a layer of thermo-material changes from a first species M1 of high hole mobility to a second species M2 of low hole mobility, for example. As the temperature increases, the proportion of charge carrier transport of the entire layer is exponentially reduced for the first species and exponentially increased for the second species. Above a critical temperature T.sub.crit, e.g., 80 C., the proportion of the charge carrier transport by the second species is so large that a voltage initially applied to the layer is no longer sufficient for the layer to have an electrically-conductive effect sufficient for the operation of an OLED.

(20) FIG. 3C shows an increase of the minimum voltage U.sub.min with the temperature T. When the minimum voltage U.sub.min reaches a threshold value U1 at a critical temperature T.sub.crit, operation at the layer stack is automatically turned-off. The voltage curve of the minimum voltage U.sub.min increases exponentially as the temperature increases. In OLEDs, the critical temperature advantageously is 80 C.

(21) FIG. 4 shows an optoelectronic component. The optoelectronic component may include a light-emitting layer stack 1 including organic layers and an electrothermal protection element connected to the layer stack 1, wherein the electrothermal protection element has a temperature-dependent resistance, wherein the electrothermal protection element includes a PTC thermistor switch R.sub.1 and a NTC thermistor switch H.sub.1, wherein the PTC thermistor switch R.sub.1 is connected in series with the layer stack, wherein the NTC thermistor switch H.sub.1 is connected in parallel with the layer stack, and wherein the electrothermal protection element is configured to decrease or interrupt an emission of light at the light-emitting layer stack 1 when a temperature of the light-emitting layer stack 1 exceeds a threshold temperature T.sub.crit.

(22) The invention is not limited to the exemplary embodiments by the description by means of these exemplary embodiments. The invention rather comprises every new feature as well as every combination of features, which in particular includes any combination of features in the claims, even if this feature of this combination is per se not explicitly stated in the claims or the exemplary embodiments.