ORGANIC ELECTROLUMINESCENT DISPLAY DEVICE AND METHOD OF PRODUCING THE SAME

• US 20090230392A1
• Filed: 03/16/2009
• Published: 09/17/2009
• Est. Priority Date: 03/17/2008
• Status: Abandoned Application

• Current Assignee: UDC Ireland Limited
• Original Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Inventors: TAKAHARA, Kazuhiro
• Application Number:
  US12/404,610
• Publication Number:
  US 20090230392A1
• Time in Patent Office: Days
• US Class Current: 257/43
• CPC Class Codes: H01L 27/1225 with semiconductor materials not belonging to the group IV of the periodic table, e.g. InGaZnO
• CPC Class Codes: H01L 27/1233 with different thicknesses of the active layer in different devices
• CPC Class Codes: H01L 27/1237 with a different composition, shape, layout or thickness of the gate insulator in different devices
• CPC Class Codes: H01L 29/7869 having a semiconductor body comprising an oxide semiconductor material, e.g. zinc oxide, copper aluminium oxide, cadmium stannate
• CPC Class Codes: H10K 59/1213 the pixel elements being TFTs

Abstract

An organic electroluminescent display device in which a plurality of light-emitting cells each having an organic electroluminescent portion are arranged on a substrate, wherein, for each of the light-emitting cells, a first transistor which controls energization on the organic electroluminescent portion, and a second transistor which switches a signal to be given to an input of the first transistor are disposed, active layers of the first and second transistors are formed by an amorphous oxide semiconductor, and, the first and second transistors are formed so that, when the first and second transistors are driven under same conditions, an amount of an output current of the first transistor is smaller than an amount of an output current of the second transistor.

Claims

1. An organic electroluminescent display device in which a plurality of light-emitting cells each having an organic electroluminescent portion are arranged on a substrate, wherein,

for each of said light-emitting cells, a first transistor which controls energization on said organic electroluminescent portion, and a second transistor which switches a signal to be given to an input of said first transistor are disposed,

active layers of said first and second transistors are formed by an amorphous oxide semiconductor, and,

said first and second transistors are formed so that, when said first and second transistors are driven under same conditions, an amount of an output current of said first transistor is smaller than an amount of an output current of said second transistor.

2. The organic electroluminescent display device according to claim 1, wherein a mobility of said first transistor is smaller than a mobility of said second transistor.

3. The organic electroluminescent display device according to claim 2, wherein an electron carrier concentration of said active layer of said first transistor is smaller than an electron carrier concentration of said active layer of said second transistor.

4. The organic electroluminescent display device according to claim 2, wherein a thickness of a gate insulating film of said first transistor is larger than a thickness of a gate insulating film of said second transistor.

5. The organic electroluminescent display device according to claim 3, wherein a thickness of a gate insulating film of said first transistor is larger than a thickness of a gate insulating film of said second transistor.

6. The organic electroluminescent display device according to claim 2, wherein a dielectric constant of a gate insulating film of said first transistor is smaller than a dielectric constant of a gate insulating film of said second transistor.

7. The organic electroluminescent display device according to claim 3, wherein a dielectric constant of a gate insulating film of said first transistor is smaller than a dielectric constant of a gate insulating film of said second transistor.

8. The organic electroluminescent display device according to claim 4, wherein a dielectric constant of a gate insulating film of said first transistor is smaller than a dielectric constant of a gate insulating film of said second transistor.

9. The organic electroluminescent display device according to claim 5, wherein a dielectric constant of a gate insulating film of said first transistor is smaller than a dielectric constant of a gate insulating film of said second transistor.

10. The organic electroluminescent display device according to claim 1, wherein the amorphous oxide semiconductor is an In—

Ga—

Zn—

O or In—

Zn—

O oxide semiconductor.

11. The organic electroluminescent display device according to claim 2, wherein the amorphous oxide semiconductor is an In—

Ga—

Zn—

O or In—

Zn—

O oxide semiconductor.

12. The organic electroluminescent display device according to claim 3, wherein the amorphous oxide semiconductor is an In—

Ga—

Zn—

O or In—

Zn—

O oxide semiconductor.

13. The organic electroluminescent display device according to claim 4, wherein the amorphous oxide semiconductor is an In—

Ga—

Zn—

O or In—

Zn—

O oxide semiconductor.

14. The organic electroluminescent display device according to claim 5, wherein the amorphous oxide semiconductor is an In—

Ga—

Zn—

O or In—

Zn—

O oxide semiconductor.

15. The organic electroluminescent display device according to claim 6, wherein the amorphous oxide semiconductor is an In—

Ga—

Zn—

O or In—

Zn—

O oxide semiconductor.

16. The organic electroluminescent display device according to claim 7, wherein the amorphous oxide semiconductor is an In—

Ga—

Zn—

O or In—

Zn—

O oxide semiconductor.

17. The organic electroluminescent display device according to claim 8, wherein the amorphous oxide semiconductor is an In—

Ga—

Zn—

O or In—

Zn—

O oxide semiconductor.

18. The organic electroluminescent display device according to claim 9, wherein the amorphous oxide semiconductor is an In—

Ga—

Zn—

O or In—

Zn—

O oxide semiconductor.

19. A method for producing an organic electroluminescent display device in which a plurality of light-emitting cells each having an organic electroluminescent portion are arranged on a substrate, and, for each of said light-emitting cells, a first transistor which controls energization on said organic electroluminescent portion, and a second transistor which switches a signal to be given to an input of said first transistor are disposed, wherein said method comprises:

a first step of forming an active layer of said first transistor and an active layer of said second transistor by an amorphous oxide semiconductor, on said substrate; and

a second step of, after only said active layer of said first transistor is covered by a light-blocking mask, irradiating said active layer of said second transistor with ultraviolet ray or plasma to make an electron carrier concentration of said active layer of said second transistor higher than an electron carrier concentration of said active layer of said first transistor.

20. A method for producing an organic electroluminescent display device in which a plurality of light-emitting cells each having an organic electroluminescent portion are arranged on a substrate, and, for each of said light-emitting cells, a first transistor which controls energization on said organic electroluminescent portion, and a second transistor which switches a signal to be given to an input of said first transistor are disposed, wherein said method comprises:

a first step of forming an active layer of said first transistor and an active layer of said second transistor by an amorphous oxide semiconductor, on said substrate;

a second step of, after only said active layer of said first transistor is covered by a light-blocking mask, irradiating said active layer of said second transistor with ultraviolet ray or plasma; and

a third step of, after only said active layer of said second transistor is covered by a light-blocking mask, irradiating said active layer of said first transistor with ultraviolet ray or plasma, and

an irradiation amount of the ultraviolet ray or plasma on said active layer of said first transistor is smaller than an irradiation amount of the ultraviolet ray or plasma on said active layer of said second transistor, so that an electron carrier concentration of said active layer of said second transistor is made higher than an electron carrier concentration of said active layer of said first transistor.