Organic EL display panel and organic EL display apparatus

• US 8,884,276 B2
• Filed: 10/25/2012
• Issued: 11/11/2014
• Est. Priority Date: 05/11/2011
• Status: Active Grant

• Current Assignee: JDI Design and Development GK
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Komatsu, Takahiro, Ohuchi, Satoru, Yamada, Ryuuta, Fujita, Hirofumi, Fujimura, Shinya, Nishiyama, Seiji, Nendai, Kenichi, Sugano, Kou, Yada, Shuhei
• Primary Examiner(s): Ho, Anthony
• Application Number:
  US13/660,291
• Publication Number:
  US 20130056719A1
• Time in Patent Office: 747 Days
• Field of Search: 257/40, 257/E51.001
• US Class Current: 257/40
• CPC Class Codes: H05B 33/26 characterised by the composition or arrangement of the conductive material used as an electrode
• CPC Class Codes: H10K 50/17 Carrier injection layers
• CPC Class Codes: H10K 59/122 Pixel-defining structures or layers, e.g. banks
• CPC Class Codes: H10K 59/131 Interconnections, e.g. wiring lines or terminals

Abstract

Provided is organic EL display panel and an organic EL display apparatus that can be driven at a low voltage and that exhibit excellent light-emitting efficiency. Included are a substrate, a first electrode, an auxiliary wiring, a hole injection layer, a functional layer, and a second electrode. The hole injection layer and the second electrode are formed to be continuous above the first electrode and above the auxiliary wiring. The second electrode and the auxiliary wiring are electrically connected by the hole injection layer in an organic EL display panel. The hole injection layer is a metal oxide film, and metal atoms constituting the metal oxide include both metal atoms at a maximum valence thereof and metal atoms at a valence less than the maximum valence. The metal oxide film includes a metal oxide crystal with a particle diameter on the order of nanometers.

Claims

1. An organic EL display panel comprising:

a substrate;

at least one first electrode on or in the substrate;

auxiliary wiring on or in the substrate at a distance from the first electrode;

a functional layer, including at least a light-emitting layer, above the first electrode;

a hole injection layer for injecting holes to the functional layer, the hole injection layer being between the first electrode and the functional layer; and

a second electrode above the functional layer, wherein

the hole injection layer and the second electrode are both formed to be continuous above the first electrode and above the auxiliary wiring,

the second electrode and the auxiliary wiring are electrically connected by the hole injection layer,

the hole injection layer includes a metal oxide film,

metal atoms constituting the metal oxide include both metal atoms at a maximum valence thereof and metal atoms at a valence less than the maximum valence, and

the metal oxide film includes a crystal of the metal oxide, a particle diameter of the crystal being on an order of nanometers.

2. The organic EL display panel of claim 1, wherein

the second electrode is a transparent electrode.

3. The organic EL display panel of claim 2, wherein

the transparent electrode is one of ITO and IZO.

4. The organic EL display panel of claim 1, wherein

the second electrode has one of Al and Ag as a primary component.

5. The organic EL display panel of claim 1, further comprising:

a metal layer formed to be continuous above the first electrode and above the auxiliary wiring, wherein

above the first electrode, the metal layer is between the second electrode and the light-emitting layer, and

above the auxiliary wiring, the metal layer is between the second electrode and the hole injection layer.

6. The organic EL display panel of claim 5, wherein

the metal layer is an electron injection layer that, above the first electrode, injects electrons from the second electrode to the light-emitting layer.

7. The organic EL display panel of claim 6, wherein

the metal layer includes barium.

8. The organic EL display panel of claim 6, wherein

at an interface between the hole injection layer and the electron injection layer, an occupied energy level of the hole injection layer causes a binding energy of the occupied energy level to be approximately equal to a Fermi level of the electron injection layer.

9. The organic EL display panel of claim 8, wherein

at the interface between the hole injection layer and the electron injection layer, a gap between the occupied energy level and the Fermi level of the electron injection layer is at most 0.3 electron volts in terms of binding energy.

10. The organic EL display panel of claim 1, wherein

the auxiliary wiring is one of ITO and IZO.

11. The organic EL display panel of claim 1, wherein

the hole injection layer above the auxiliary wiring has properties identical to the hole injection layer above the first electrode.

12. The organic EL display panel of claim 1, wherein

at least above the auxiliary wiring, the hole injection layer is at least 4 nm thick.

13. The organic EL display panel of claim 1, further comprising:

a bank on the hole injection layer defining at least one aperture exposing the first electrode and including a region exposing the auxiliary wiring, wherein

the light-emitting layer is formed above the first electrode in the aperture defined by the bank.

14. The organic EL display panel of claim 13, wherein

the at least one first electrode comprises a plurality of first electrodes, one per pixel, and

the at least one aperture in the bank comprises a plurality of apertures formed in one-to-one correspondence with the first electrodes.

15. The organic EL display panel of claim 13, wherein

the at least one first electrode comprises a plurality of first electrodes, one per pixel, arranged in lines, and

the at least one aperture in the bank comprises a plurality of apertures, one for each of the lines of the first electrodes.

16. The organic EL display panel of claim 1, wherein

the hole injection layer is at least 2 nm thick.

17. The organic EL display panel of claim 1, wherein

a UPS spectrum of the hole injection layer exhibits an upward protrusion in a range between 1.8 electron volts and 3.6 electron volts lower than a lowest energy level of a valence band in terms of binding energy.

18. The organic EL display panel of claim 1, wherein

an XPS spectrum of the hole injection layer exhibits an upward protrusion in a range between 1.8 electron volts and 3.6 electron volts lower than a lowest energy level of a valence band in terms of binding energy.

19. The organic EL display panel of claim 1, wherein

a differential spectrum obtained by differentiating a UPS spectrum of the hole injection layer exhibits a shape expressed by a non-exponential function throughout a range between 2.0 electron volts and 3.2 electron volts lower than a lowest energy level of a valence band in terms of binding energy.

20. The organic EL display panel of claim 1, wherein

an occupied energy level of the hole injection layer is in a range between 2.0 electron volts and 3.2 electron volts lower than a lowest energy level of a valence band in terms of binding energy.

21. The organic EL display panel of claim 1, wherein

at an interface between the hole injection layer and the functional layer, an occupied energy level of the hole injection layer causes a highest occupied molecular orbital of the functional layer, to be approximately equal to the occupied energy level in terms of binding energy.

22. The organic EL display panel of claim 21, wherein

at the interface between the hole injection layer and the functional layer, a gap between the occupied energy level and the highest occupied molecular orbital of the functional layer is at most 0.3 electron volts in terms of binding energy.

23. The organic EL display panel of claim 1, wherein

at an interface between the first electrode and the hole injection layer, an occupied energy level of the hole injection layer causes a binding energy of the occupied energy level to be approximately equal to a Fermi level of the first electrode.

24. The organic EL display panel of claim 23, wherein

at the interface between the first electrode and the hole injection layer, a gap between the occupied energy level and the Fermi level of the first electrode is at most 0.3 electron volts in terms of binding energy.

25. The organic EL display panel of claim 1, wherein

at an interface between the auxiliary wiring and the hole injection layer, an occupied energy level of the hole injection layer causes a binding energy of the occupied energy level to be approximately equal to a Fermi level of the auxiliary wiring.

26. The organic EL display panel of claim 25, wherein

at the interface between the auxiliary wiring and the hole injection layer, a gap between the occupied energy level and the Fermi level of the auxiliary wiring is at most 0.3 electron volts in terms of binding energy.

27. The organic EL display panel of claim 1, wherein

at an interface between the hole injection layer and the second electrode, an occupied energy level of the hole injection layer causes a binding energy of the occupied energy level to be approximately equal to a Fermi level of the second electrode.

28. The organic EL display panel of claim 27, wherein

at the interface between the hole injection layer and the second electrode, a gap between the occupied energy level and the Fermi level of the second electrode is at most 0.3 electron volts in terms of binding energy.

29. The organic EL display panel of claim 1, wherein

the metal oxide is tungsten oxide, and

the metal atoms at the maximum valence are tungsten atoms with a valence of six.

30. The organic EL display panel of claim 29, wherein

the metal atoms at the valence less than the maximum valence are tungsten atoms with a valence of five.

31. The organic EL display panel of claim 30, wherein

a ratio W⁵⁺/W⁶⁺ of the number of the tungsten atoms with a valence of five to the number of the tungsten atoms with a valence of six is at least 3.2%.

32. The organic EL display panel of claim 31, wherein

the ratio W⁵⁺/W⁶⁺ is at least 3.2% and at most 7.4%.

33. The organic EL display panel of claim 29, wherein

a hard X-ray photoelectron spectroscopy spectrum of the hole injection layer formed from tungsten oxide includes a first component and a second component, the first component corresponding to a 4f_7/2 energy level of the tungsten atoms with a valence of six, and the second component being in a region lower than the first component in tel ins of binding energy.

34. The organic EL display panel of claim 33, wherein

the second component is in a region between 0.3 electron volts and 1.8 electron volts lower, in terms of binding energy, than a peak top of the first component.

35. The organic EL display panel of claim 33, wherein

an area intensity of the second component is between 3.2% and 7.4% of an area intensity of the first component.

36. The organic EL display panel of claim 29, wherein

tungsten atoms at a valence less than the maximum valence cause an electronic state of the hole injection layer formed from tungsten oxide to have an occupied energy level in a range between 1.8 electron volts and 3.6 electron volts lower than a lowest energy level of a valence band in terms of binding energy.

37. The organic EL display panel of claim 29, wherein

the hole injection layer formed from tungsten oxide includes a plurality of crystals of the tungsten oxide, each of the crystals having a particle diameter of between 5 nm and 10 nm.

38. The organic EL display panel of claim 29, wherein

regular linear structures at intervals of between 1.85 angstroms and 5.55 angstroms appear in a lattice image by transmission electron microscopy observation of the hole injection layer formed from tungsten oxide.

39. The organic EL display panel of claim 38, wherein

in a 2D Fourier transform image of the lattice image, a bright region formed by concentric circles centering on a center point of the 2D Fourier transform image appears.

40. The organic EL display panel of claim 39, wherein

in a plot of distance from the center point versus normalized luminance, the normalized luminance being a normalized value of the luminance of the 2D Fourier transform image at the corresponding distance, at least one peak of the normalized luminance appears other than the center point.

41. The organic EL display panel of claim 40, wherein

with a peak width being a difference between the distance corresponding to a position of a peak top of the normalized luminance appearing closest to the center point in the plot and the distance corresponding to a position at which a peak of the normalized luminance begins to rise, the peak width is less than 22 when the distance corresponding to the peak top is 100.

42. An organic EL display panel comprising:

a substrate;

a first electrode on or in the substrate;

wiring on or in the substrate at a distance from the first electrode;

an organic layer, including organic material, above the first electrode;

a metal oxide film, including a metal oxide, between the organic layer and the first electrode; and

a second electrode above the organic layer, wherein

the metal oxide film and the second electrode are both formed to be continuous above the first electrode and above the wiring,

the second electrode and the wiring are electrically connected by the metal oxide film,

metal atoms constituting the metal oxide include both metal atoms at a maximum valence thereof and metal atoms at a valence less than the maximum valence, and

the metal oxide film includes a crystal of the metal oxide, a particle diameter of the crystal being on an order of nanometers.

43. A method of manufacturing an organic EL display panel, comprising the steps of:

forming a first electrode on or in a substrate;

forming auxiliary wiring on or in the substrate at a distance from the first electrode;

forming a hole injection layer to be continuous above the first electrode and above the auxiliary wiring;

forming a functional layer above the first electrode including at least a light-emitting layer; and

forming a second electrode to be continuous above the functional layer and above the hole injection layer formed above the auxiliary wiring, wherein

the second electrode and the auxiliary wiring are electrically connected by the hole injection layer,

the hole injection layer is formed to include a metal oxide film, and

the metal oxide film is formed so that metal atoms constituting the metal oxide include both metal atoms at a maximum valence thereof and metal atoms at a valence less than the maximum valence, and so as to include a crystal of the metal oxide, a particle diameter of the crystal being on an order of nanometers.