Organic electronic/optoelectronic devices

1. A p-type semiconductor device comprising:

a semiconductor layer,

wherein the semiconductor layer comprises at least a semiconductive organic material, and at least one additive in an amount of at least 0.1% by weight relative to the semiconductive organic material, which additive occupies at least some voids within the semiconductive organic material occupiable by water molecules, and has a smaller charge carrier trapping effect on the semiconductive organic material than water, and

wherein the additive comprises a material having an electron affinity less than the ionization potential of the semiconductive organic material by at least 0.3 eV.

2. The device according to claim 1 , wherein said device is an electronic switching device and the at least one additive reduces the threshold voltage change of the electron switching device to less than 1V in a stress test involving operating the electronic switching device in a saturation regime at a drain current of about 2.5 μA for a period of 25 hours.

3. The device according to claim 1 , wherein the device is an electronic switching device, and the additive comprises a material having an electron affinity less than the ionization potential of the semiconductive organic material by at least 0.5 eV.

4. The device according to claim 1 , wherein the additive comprises a molecular material having a molecular weight of less than 5% of the number average molecular weight of the semiconductive organic material.

5. The device according to claim 1 , wherein the additive has a higher solubility at room temperature in the organic semiconductive material than water has in the organic semiconductive material.

6. The device according to claim 1 , wherein the additive has a solubility of at least 0.1% in water.

7. The device according to claim 1 , wherein the semiconductor layer comprises residual water molecules in an amount of at least 0.1% by weight.

8. The device according to claim 1 , wherein the semiconductor layer is encapsulated together with one or more other layers of the device against the ingress of oxygen.

9. The device according to claim 1 , wherein said additive is solid at room temperature and has a solid solubility higher than 1% by weight in the semiconductive organic material.

10. The device according to claim 1 , wherein the amount of said additive is at least 1% by weight relative to the semiconductive organic material.

11. The device according to claim 2 , wherein the at least one additive reduces the threshold voltage change of the electron switching device to less than 0.7V in said stress test.

12. A p-type semiconductor device comprising:

a semiconductor layer, wherein the semiconductor layer comprises at least a semiconductive organic material, water species, and at least one additive in an amount of at least 0.1% by weight relative to the semiconductive organic material, which additive at least partly negates a charge carrier trapping effect caused by the water species on the semiconductive organic material,

wherein the additive comprises a material having an electron affinity less than the ionization potential of the semiconductive organic material by at least 0.3 eV, and

wherein the device is an electronic switching device, and the additive comprises a material having an ionization potential greater than the ionization potential of the semiconductive organic material by at least 0.3 eV.

13. The device according to claim 12 , wherein the additive comprises a material having an ionization potential greater than the ionization potential of the semiconductive organic material by at least 0.5 eV.

14. The device according to claim 12 , wherein the additive comprises a material having an ionization potential greater than the ionization potential of the semiconductive organic material by at least 1 eV.

15. A p-type semiconductor device comprising:

a semiconductor layer, wherein the semiconductor layer comprises at least a semiconductive organic material, water species, and at least one molecular additive in an amount of at least 0.1% by weight relative to the semiconductive organic material, which molecular additive at least partly negates a charge carrier trapping effect caused by the water species on the semiconductive organic material,

wherein the molecular additive comprises a material having an electron affinity less than the ionization potential of the semiconductive organic material by at least 0.3 eV,

wherein said molecular additive is liquid at room temperature and is a solvent for the semiconductive organic material, and

wherein the solubility of the semiconductive organic material in the liquid molecular additive is at least 0.1% by weight.

16. The device according to claim 15 , wherein the boiling point of said additive is higher than 150° C.

17. A p-type semiconductor device comprising:

a semiconductor layer, wherein the semiconductor layer comprises at least a semiconductive organic material, water species, and at least one molecular additive in an amount of at least 0.1% by weight relative to the semiconductive organic material, which molecular additive at least partly negates a charge carrier trapping effect caused by the water species on the semiconductive organic material,

wherein the molecular additive comprises a material having an electron affinity less than the ionization potential of the semiconductive organic material by at least 0.3 eV,

wherein said device is an electronic switching device and the incorporation of the molecular additive reduces the threshold voltage shift of the electronic switching device in a stress test by 50% compared to that of a reference device, in which no molecular additive is incorporated in said semiconductive organic material, and

wherein said stress test involves operating the device in the saturation regime at a drain current of about (0.25 μA×W/L) for a period of 25 hours, where W and L are the channel width and channel length of the electronic switching device.