Photolithographic patterning of organic electronic devices
A method of making an OLED device includes providing a first undercut lift-off structure over the device substrate having a first array of bottom electrodes. Next, one or more first organic EL medium layers including at least a first light-emitting layer are deposited over the first undercut lift-off structure and over the first array of bottom electrodes. The first undercut lift-off structure and overlying first organic EL medium layer(s) are removed by treatment with a first lift-off agent comprising a fluorinated solvent to form a first intermediate structure. The process is repeated using a second undercut lift-off structure to deposit one or more second organic EL medium layers over a second array of bottom electrodes. After removal of the second undercut lift-off structure, a common top electrode is provided in electrical contact with the first and second organic EL medium layers.
1. A method of making an OLED device, the method comprising:
a) providing a device substrate having a first array of bottom electrodes and a second array of bottom electrodes;
b) providing over the device substrate a first undercut lift-off structure having a first pattern of openings corresponding to the first array of bottom electrodes;
c) depositing one or more first organic EL medium layers, including at least a first light-emitting layer, and a first top electrode layer over the first undercut lift-off structure and over the first array of bottom electrodes;
d) removing the first undercut lift-off structure, the one or more first organic EL medium layers overlaying the first undercut lift-off structure and first top electrode overlaying the first undercut lift-off structure to form a first intermediate structure;
e) providing over the first intermediate structure a second undercut lift-off structure having a second pattern of openings corresponding to the second array of bottom electrodes;
f) depositing one or more second organic EL medium layers, including at least a second light-emitting layer, and a second top electrode over the second undercut lift-off structure and over the second array of bottom electrodes;
g) removing the second undercut lift-off structure, the one or more second organic EL medium layers overlaying the second undercut lift-off structure and second top electrode overlaying the second undercut lift-off structure to form a second intermediate structure; and
h) providing a common top electrode to electrically connect the first and second top electrode layers.
2. The method of claim 1 , wherein at least one lift-off structure includes at least two patterned layers including a fluorinated material base layer and an overlying photoresist layer, wherein the fluorinated material base layer is undercut relative to the photoresist layer.
3. The method of claim 1 , wherein at least one lift-off structure includes a patterned fluorinated photoresist developed using a fluorinated solvent and having an undercut profile.
4. The method of claim 1 , further including a dry-etch cleaning step between steps (b) and (c) or between steps (e) and (f) or both.
5. The method of claim 1 , wherein at least one lift-off structure comprises a negative tone photosensitive film that absorbs or blocks at least 80% of imaging radiation used in the formation of the lift-off structure.
6. The method of claim 1 , wherein the first or second top electrodes or both absorb or block at least 80% of imaging radiation.
7. The method of claim 1 , wherein at least one lift-off structure is removed using a lift-off agent and wherein the lift-off agent comprises a fluorinated solvent.
8. The method of claim 1 , wherein the device substrate further has a third array of bottom electrodes, the method further comprising, prior to step (h),
providing over the second intermediate structure a third undercut lift-off structure having a third pattern of openings corresponding to a third array of bottom electrodes;
depositing one or more third organic EL medium layers, including at least a third light-emitting layer, and a third top electrode over the third undercut lift-off structure and over the third array of bottom electrodes;
removing the third undercut lift-off structure, the one or more third organic EL medium layers overlaying the third undercut lift-off structure and third top electrode over the third undercut lift-off structure to form a third intermediate structure.
9. The method of claim 1 , further comprising, prior to step (h), cleaning the surface of the top electrodes of residual fluorinated material.
10. The method of claim 9 , wherein the cleaning comprises contact with a cleaning agent comprising a fluorinated solvent and a protic solvent.
11. The method of claim 9 , wherein the cleaning comprises dry etching.
12. The method of claim 11 , wherein the dry etching includes an argon plasma or a substantially non-oxidizing plasma.
13. The method of claim 1 , further comprising, prior to step (h) treating the top electrodes with a low work-function metal, the low work-function metal comprising an alkali metal or an alkaline earth metal.
14. The method of claim 1 , further comprising, prior to step (h) treating the top electrodes with a reducing gas environment comprising hydrogen.
15. The method of claim 1 , wherein the material used for the common top electrode is different than the material used for the first or second top electrodes.
16. The method of claim 1 , wherein at least one lift-off structure includes at least two patterned layers including a fluorinated material base layer and an overlying photoresist layer, the overlying photoresist layer provided from a photoresist composition comprising a fluorinated coating solvent.
17. The method of claim 16 , wherein the fluorinated coating solvent comprises a hydrofluoroether.
18. The method of claim 17 , wherein the photoresist layer comprises a fluorinated photoresist.
19. The method of claim 16 , wherein the fluorinated material base layer includes a cyclic perfluorinated polymer.