Organic field-effect transistor and circuit

• US 8,071,976 B2
• Filed: 08/03/2009
• Issued: 12/06/2011
• Est. Priority Date: 08/04/2008
• Status: Active Grant

• Current Assignee: Novaled AG
• Original Assignee: Novaled AG
• Inventors: Huang, Qiang, Canzler, Tobias, Denker, Ulrich, Werner, Ansgar, Leo, Karl, Harada, Kentaro
• Primary Examiner(s): Mandala, Victor A
• Application Number:
  US12/534,402
• Publication Number:
  US 20100065833A1
• Time in Patent Office: 855 Days
• Field of Search: 257/40, 257/288, 257/E51.005, 257/E51.006
• US Class Current: 257/40
• CPC Class Codes: H10K 10/486 the channel region comprising two or more active layers, e.g. forming pn heterojunctions
• CPC Class Codes: H10K 19/10 comprising field-effect transistors
• CPC Class Codes: H10K 71/30 Doping active layers, e.g. electron transporting layers

Abstract

The invention relates to an organic field-effect transistor, in particular an organic thin film field-effect transistor comprising a gate electrode, a drain electrode and a source electrode, a dielectric layer which is formed in contact with the gate electrode, an active layer made from an organic material which is in contact with the drain electrode and the source electrode and which is configured electrically undoped, a dopant material layer which contains a dopant material that is an electrical dopant for the organic material of the active layer, and a border surface region in which a planar contact is formed between the active layer and the dopant material layer, wherein mobility of similar electrical charge carriers, namely electrons or holes, in the dopant material layer is no more than half as great as in the active layer.

Claims

1. An organic field-effect transistor comprising:

a gate electrode, a drain electrode and a source electrode,

a dielectric layer, wherein the dielectric layer is in contact with the gate electrode,

an active layer comprising an organic material, wherein the active layer is in contact with the drain electrode and the source electrode, wherein the active layer is electrically undoped, and wherein the active layer comprises a conduction channel between the drain electrode and the source electrode during operation,

a dopant material layer, wherein the dopant material layer comprises a dopant material that is an electrical dopant for the organic material of the active layer, and

a border surface region wherein a planar contact exists between the conduction channel of the active layer and the dopant material layer, and wherein a mobility of electrical charge carriers in the dopant material layer is no more than half a mobility of electrical charge carriers in the active layer.

2. The field-effect transistor according to claim 1, wherein the dopant material layer consists of the dopant material.

3. The field-effect transistor according to claim 1, wherein the dopant material layer is embedded in a matrix material for which the dopant material is not an electrical dopant.

4. The field-effect transistor according to claim 3, wherein an energy difference for charge transfer between the dopant material and the matrix material is greater than about 0.5 eV.

5. The field-effect transistor according to claim 1, wherein the dopant material layer comprises multiple layers, wherein one partial layer consists of the dopant material and another partial layer, which is arranged between the partial layer and the active layer and is in contact with the partial layer and the active layer consists of a matrix material which transports the charge carrier.

6. The field-effect transistor according to claim 4, wherein the matrix material transporting charge carriers comprises a material which transports electrons.

7. The field-effect transistor according to claim 4, wherein the matrix material transporting charge carriers comprises a material which transports holes.

8. The field-effect transistor according to claim 1, wherein the dopant material layer is in direct contact with the drain electrode and the source electrode.

9. The field-effect transistor according to claim 1, wherein, in a switched-on state in which the conduction channel is in the active layer, an electrical conductivity in the active layer is greater than in the dopant material layer by at least a factor of two.

10. The field-effect transistor according to claim 1, wherein the dopant material is a molecular dopant material which comprises at least two different atoms.

11. The field-effect transistor according to claim 10, wherein the molecular dopant material has a molar mass of between about 100 g/mol and about 2000 g/mol.

12. The field-effect transistor according to claim 1, wherein an energetic difference between the highest occupied orbital of the molecules (HOMO) of the organic material of the active layer and the lowest unoccupied orbital of the molecules (LUMO) of the dopant material is greater than about −

0.5 eV if the dopant material for the organic material of the active layer is an acceptor.

13. The field-effect transistor according to claim 1, wherein an energetic difference between the lowest unoccupied orbital of the molecules (LUMO) of the organic material of the active layer and the highest occupied orbital of the molecules (HOMO) of the dopant material is less than about 0.5 eV if the dopant material for the organic material of the active layer is a donor.

14. The field-effect transistor according to claim 1, wherein the dopant material layer comprises an encapsulation layer.

15. The field-effect transistor according to claim 14, wherein the encapsulation layer is free from direct contact with the drain electrode and the source electrode.

16. The field-effect transistor according to claim 1, wherein the dopant material layer comprises a charge carrier injection layer in direct contact with the drain electrode and the source electrode.