Organic electroluminescent devices
View Patent ↗The invention relates to an organic electroluminescent device ( 1 ) comprising a substrate ( 2 ), at least one electroluminescent layer stack on top of the substrate ( 2 ) with at least a substrate electrode ( 3 ), a counter electrode ( 5 ) and at least one organic electroluminescent layer ( 4 ) arranged between substrate electrode ( 2 ) and counter electrode ( 5 ), and a short prevention layer ( 6 ) covering the counter electrode ( 5 ) establishing a double layer (DL) with a tensile stress (TS) induced by the short prevention layer ( 5 ), and an electrically isolating layer ( 8 ) at least partly covering the short prevention layer ( 6 ), wherein the electrically isolating layer ( 8 ) is suitable to partially dissolve the organic layer ( 4 ) in the vicinity of a defect ( 7 ) within the electroluminescent layer stack and the tensile stress (TS) induced by the short prevention layer ( 6 ) is suitable to roll up ( 10 ) the double layer (DL) adjacent to the defect ( 7 ) after deposition of the electrically isolating layer ( 8 ). The invention further relates to a method to manufacture such OLED devices ( 1 ) and the use of a short prevention layer ( 6 ) to prevent shorts in such OLED devices ( 1 ).
1. An organic electroluminescent device comprising a substrate, at least one electroluminescent layer stack on top of the substrate with at least a substrate electrode, a counter electrode and at least one organic electroluminescent layer arranged between the substrate electrode and the counter electrode, and a short prevention layer covering the counter electrode establishing a double layer (DL), wherein the short prevention layer has a thickness that provides a tensile stress (TS) in the double layer, and an electrically isolating layer at least partly covering the short prevention layer, wherein the electrically isolating layer is suitable to partially dissolve the organic layer in the vicinity of a defect within the electroluminescent layer stack and the tensile stress (TS) provided by the short prevention layer is suitable to roll up the double layer (DL) adjacent to the defect after deposition of the electrically isolating layer.
2. The organic electroluminescent device according to claim 1 , wherein the short prevention layer comprises at least one material selected from the group consisting of manganese, copper, magnesium fluoride, silver, and combinations thereof.
3. The organic electroluminescent device according to claim 1 , wherein the thickness of the short prevention layer is adapted to provide the tensile stress (TS) such that the tensile stress (TS) is suitable to roll up the counter electrode adjacent to the defect after deposition of the isolating layer.
4. The organic electroluminescent device according to claim 1 , wherein the thickness of the counter electrode is below 140 nm.
5. The organic electroluminescent device according to claim 1 , wherein the electrically isolating layer has a layer thickness of at least 1 micrometer.
6. The organic electroluminescent device according to claim 1 , wherein the electrically isolating layer is a polymer layer comprising solvents or reactive components.
7. A method for manufacturing an organic electroluminescent device, comprising:
depositing a short prevention layer on top of a counter electrode, said short prevention layer having a tensile stress (TS) suitable to roll up a double layer (DL) of the counter electrode and the short prevention layer adjacent to a defect within an electroluminescent layer stack of the device,
depositing an electrically isolating layer on top of the short prevention layer that at least partly covers the short prevention layer,
dissolving at least one organic electroluminescent layer of the stack arranged between a substrate electrode and the counter electrode in a vicinity of the defect by the previously deposited electrically isolating layer,
rolling-up the double layer (DL) of the counter electrode and the short prevention layer adjacent to the defect, wherein said rolling-up is induced by the tensile stress present within the double layer (DL), and
hardening or curing the electrically isolating layer.
8. The method according to claim 7 , wherein the short prevention layer is deposited by vacuum evaporation.
9. The method according to claim 7 , wherein the electrically isolating layer is fully covering the counter electrode and the short prevention layer.
10. The method according to claim 7 , wherein the electrically isolating layer is deposited by spray coating or by screen printing or tampon printing.
11. The method according to claim 10 , further comprising the step of curing the electrically isolating layer after deposition via exposure of the deposited electrically isolating layer to at least one of ultra violet light or enhanced temperature.
12. The organic electroluminescent device according to claim 1 , wherein the thickness of the short prevention layer is more than 20 nm.
13. The organic electroluminescent device according to claim 1 , wherein the counter electrode has a layer thickness that is between 10 and 100 nm.
14. The organic electroluminescent device according to claim 1 , wherein the electrically isolating layer has a layer thickness of more than 5 micrometers.