Processes for making light extraction substrates for an organic light emitting diode using photo-thermal treatment
A process includes providing a base substrate and disposing a precursor on the base substrate. The precursor includes powdered particles of a first material and an organic binder. The process includes photo-thermally treating the precursor to form a light extraction layer. The photo-thermal treatment includes exposing the precursor to a flash lamp that is energized in pulses. The process further includes disposing an organic light emitting diode adjacent to the light extraction layer.
1. A process for forming an article for improved light extraction, the process comprising:
providing a base substrate;
disposing a precursor on the base substrate, the precursor comprising:
particles of a first material comprising an inorganic oxide and having:
an average diameter of from 10 nm to 1 μm; and
an organic binder; and
photo-thermally treating the precursor to form a porous photo-thermally treated light extraction layer having an average pore diameter from 10 nm to 1000 nm,
wherein the photo-thermally treating comprises exposing the precursor to a radiation source emitting radiation in at least the range from 300 to 400 nm and the porous photo-thermally treated light extraction layer improves the light output of the article by a factor of 1.7× or greater.
2. The process of claim 1 , wherein the process further comprises coating the photo-thermally treated light extraction layer with a second layer comprising an inorganic polymer and disposing an organic light emitting diode adjacent to the inorganic polymer.
3. The process of claim 2 , further comprising disposing an organic light emitting diode layer adjacent to the light extraction layer.
4. The process of claim 1 , wherein the radiation source comprises a pulsed radiation source having a pulse width of from 1 μs to 100 ms measured at ⅓ peak value.
5. The process of claim 4 , wherein pulses from the pulsed radiation source have an energy per pulse of from 1 to 5000 J.
6. The process of claim 4 , wherein pulses from the pulsed radiation source have an energy per pulse delivered to the material of from 0.01 to 1 J/cm 2 /pulse.
7. The process of claim 4 , wherein the total energy delivered to the material is from 0.1 to 100 J/cm 2 .
8. The process of claim 4 , wherein pulses from the pulsed radiation source comprise at least two different stages, a first stage comprising an initial part of the pulse and a second stage, comprising a subsequent part of the pulse, wherein each stage comprises a pulse energy and pulse duration.
9. The process of claim 8 , wherein the first stage has an energy/pulse of 100-5000 J/pulse and a duration from 0.1 ms to 10 ms and the second stage has an energy/pulse of 100-5000 J/pulse and a duration from 0.1 ms to 10 ms.
10. The process of claim 8 , wherein the first stage has a duration of from 100 μs to 300 μs and the second stage has a duration of from 1000 μs to 3000 μs.
11. The process of claim 8 , wherein the first stage has a total energy delivered to the material from 0.1 to 100 J/cm 2 .
12. The process of claim 11 , wherein the first stage has a peak energy that is 1.5 to 10× higher than the peak energy of the second stage.
13. The process of claim 8 , wherein the ratio of total energy delivered to the material in the first stage/second stage is from 1-4.
14. The process of claim 8 , wherein the process further comprises a starter pulse that has an energy/pulse of 2-10× the energy/pulse value of the first stage pulse.
15. The process of claim 1 , wherein the overall duration of the photo-thermally treating is from 20 seconds to 10 minutes.
16. The process of claim 1 , wherein a maximum temperature during the photo-thermally treating is 150° C. or less.
17. The process of claim 1 , wherein the particles of the first material comprise TiO 2 .
18. The process of claim 1 , wherein the base substrate comprises a continuous, flexible sheet, and the process comprises a roll-to-roll process.
19. The process of claim 18 , wherein the continuous, flexible sheet comprises a glass sheet with a thickness of 100 μm or less.
20. A process for forming an article for improved light extraction, the process comprising:
providing a base substrate;
disposing a two-layer precursor on the base substrate, the two-layer precursor comprising:
a first layer adjacent to the base substrate, the first layer comprising:
an inorganic oxide having an average diameter from 10 nm to 1 μm, and
an organic binder; and
a second layer adjacent to the first layer, the second layer comprising:
an inorganic polymer smoothing layer;
wherein the first layer and second layer are substantially unmixed; and
acting on the two-layer precursor to form a light extraction layer having an average pore diameter from 10 nm to 1000 nm; wherein acting comprises photo-thermally treating at least one layer of the two-layer precursor; and
wherein:
the photo-thermally treating comprises exposing the precursor to a radiation source emitting radiation in at least the range from 300 to 400 nm, and
the porous photo-thermally treated light extraction layer improves the light output of the article by a factor of 1.7× or greater.
21. The process of claim 20 , further comprising disposing a light generation layer adjacent to the second layer, wherein disposing the light generation layer adjacent to the photo-thermally treated light extraction layer comprises fabricating the organic light emitting diode on the planarization layer.
22. The process of claim 20 , wherein the radiation source comprises a pulsed radiation source having a pulse width of from 1 μs to 100 ms measured at ⅓ peak value.
23. The process of claim 22 , wherein pulses from the pulsed radiation source have an energy per pulse of from 1 to 5000 J.
24. The process of claim 23 , wherein pulses from the pulsed radiation source have an energy per pulse delivered to the material of from 0.01 to 1 J/cm 2 /pulse.
25. The process of claim 22 , wherein the total energy delivered to the material is from 0.1 to 100 J/cm 2 .
26. The process of claim 22 , wherein pulses from the pulsed radiation source comprise at least two different stages, a first stage comprising an initial part of the pulse and a second stage, comprising a subsequent part of the pulse, wherein each stage comprises a pulse energy and pulse duration.
27. The process of claim 26 , wherein the first stage has an energy/pulse of 100-5000 J/pulse and a duration from 0.1 ms to 10 ms and the second stage has an energy/pulse of 100-5000 J/pulse and a duration from 0.1 ms to 10 ms.
28. The process of claim 26 , wherein the first stage has a duration of from 100 μs to 300 μs and the second stage has a duration of from 1000 μs to 3000 μs.
29. The process of claim 26 , wherein the first stage has a total energy delivered to the material from 0.1 to 100 J/cm 2 .
30. The process of claim 29 , wherein the first stage has a peak energy that is 1.5 to 10× higher than the peak energy of the second stage.
31. The process of claim 26 , wherein the ratio of total energy delivered to the material in the first stage/second stage is from 1-4.
32. The process of claim 26 , wherein the process further comprises a starter pulse that has an energy/pulse of 2-10× the energy/pulse value of the first stage pulse.
33. The process of claim 20 , wherein the overall duration of the photo-thermally treating is from 20 seconds to 10 minutes.
34. The process of claim 20 , wherein a maximum temperature during the photo-thermally treating is 150° C. or less.
35. The process of claim 20 , wherein the particles of the inorganic oxide comprise TiO 2 .