Metallic layer comprising alkali metal and second metal
The present invention relates to a metallic layer adjacent to a semiconducting layer comprising a substantially covalent matrix material, the metallic layer comprising at least one first metal and at least one second metal, wherein a) the first metal is selected from the group consisting of Li, Na, K, Rb, Cs; and b) the second metal is selected from the group consisting of Zn, Hg, Cd, Te, electronic devices comprising such materials and process for preparing the same.
1. A metallic layer adjacent to a semiconducting layer comprising a substantially covalent matrix material, the metallic layer comprising at least one first metal and at least one second metal, wherein
a) the first metal is selected from the group consisting of Li, Na, K, Rb, and Cs; and
b) the second metal is selected from the group consisting of Zn, Hg, Cd, and Te,
wherein the metallic layer is substantially isotropic, and
wherein the at least one first metal and the at least one second metal are present in the metallic layer at a total amount of at least 90 wt %, based on the weight of the metallic layer.
2. The metallic layer according to claim 1 , wherein the metallic layer has thickness in the range 1-100 nm.
3. The metallic layer according to claim 1 , wherein the first metal is selected as Na or Li and/or the second metal is selected as Zn and/or Te.
4. An electronic device comprising at least two distinct layers sandwiched between a first electrode and a second electrode, wherein the distinct layers comprise the metallic layer adjacent to the semiconducting layer according to claim 1 .
5. The electronic device according to claim 4 which is an organic light emitting diode or an organic photovoltaic device.
6. The electronic device according to claim 4 , wherein the metallic layer is adjacent to one of the electrodes.
7. The electronic device according to claim 4 , wherein the metallic layer is an electron injection layer or a part of a charge generation layer.
8. A process for preparation of the metallic layer according to claim 1 , the process comprising the steps
(i) providing the semiconducting layer,
(ii) co-vaporizing, at a pressure less than 10 −2 Pa, a composition provided in a vaporization source which is heated to a temperature between 100° C. and 600° C., wherein the composition comprises
a) at least one first metal selected from the group consisting of Li, Na, K, Rb, and Cs; and
b) at least one second metal selected from the group consisting of Zn, Hg, Cd, and Te, and
(iii) at least one subsequent step of co-deposition, wherein the first metal and the second metal are deposited on a surface, wherein the surface is the surface of the semiconducting layer provided in the step (i) and the surface has a temperature which is below the temperature of the vaporization source.
9. The process according to claim 8 , wherein the composition is substantially metallic.
10. The process according to claim 9 , wherein the substantially metallic composition is a metal alloy and the temperature of the vaporization source is lower than the melting point of the metal alloy.
11. The process according to claim 9 , wherein the composition is a metal alloy, and the metal alloy comprises a homogeneous phase comprising the first metal and the second metal.
12. The process according to claim 9 , wherein the substantially metallic composition is a metal alloy, and the metal alloy has a higher melting point than the first metal and/or the second metal.
13. The process according to claim 8 , wherein the first metal is sodium and/or the second metal is zinc.
14. A process for preparation of an electronic device comprising at least two distinct layers sandwiched between a first electrode and a second electrode, wherein the distinct layers comprise a metallic layer adjacent to a semiconducting layer comprising a substantially covalent matrix material, the metallic layer comprising at least one first metal and at least one second metal, wherein
a) the first metal is selected from the group consisting of Li, Na, K, Rb, and Cs; and
b) the second metal is selected from the group consisting of Zn, Hg, Cd, and Te,
the process comprising the steps
(i) providing the first electrode,
(ii) providing the semiconducting layer and the metallic layer by a process for preparation of the metallic layer according to claim 1 , the process comprising the steps
(A) providing the semiconducting layer,
(B) co-vaporizing, at a pressure less than 10 −2 Pa, a composition provided in a vaporization source which is heated to a temperature between 100° C. and 600° C., wherein the composition comprises
a) at least one first metal selected from the group consisting of Li, Na, K, Rb, and Cs; and
b) at least one second metal selected from the group consisting of Zn, Hg, Cd, and Te, and
(C) at least one subsequent step of co-deposition, wherein the first metal and the second metal are deposited on a surface, wherein the surface is the surface of the semiconducting layer provided in the step (i) and the surface has a temperature which is below the temperature of the vaporization source, and
(iii) providing the second electrode.
15. A use of a metal alloy, the alloy comprising at least one homogeneous phase comprising at least one first metal selected from Li, Na, K, Rb and Cs and at least one second metal selected from Zn, Cd, Hg and Te, for
(i) preparing of the metallic layer according to claim 1 , and/or
(ii) preparing of an electronic device comprising the metallic layer according to claim 1 .
16. The metallic layer according to claim 3 , wherein the first metal is selected as Na and the second metal is selected as Zn.
17. The electronic device according to claim 7 , wherein the metallic layer is an electron injecting part of the charge generation layer.
18. The electronic device according to claim 4 , wherein the electronic device comprises other parts of the device arranged outside the space between the electrodes.
19. The process according to claim 14 , wherein step (i) of the process further comprises providing further layers arranged between the first electrode and the semiconducting layer.
20. The process according to the claim 14 , wherein step (iii) of the process further comprises providing any other parts of the device arranged outside the space between the electrodes after providing the second electrode.
21. The process according to claim 14 wherein step (iii) further comprises providing remaining layers between the metallic layer and the second electrode before providing the second electrode.