Solar cell
A solar cell includes a semiconductor layer, a collecting layer for collecting free charge carriers from the semiconductor layer and a buffer layer which is arranged between the semiconductor layer and the collecting layer. The buffer layer is designed as a tunnel contact between the semiconductor layer and the collecting layer. The buffer layer essentially includes a material with a surface charge density of at least 10 12 cm −2 , preferably of at least 5×10 12 cm −2 , and more preferably of at least 10 13 cm −2 .
1. A solar cell comprising:
a semiconductor layer in the form of a wafer or a layer vapor-deposited onto a substrate in a thin-film process, a collecting layer for collecting free charge carriers from the semiconductor layer and a buffer layer which is arranged between the semiconductor layer and the collecting layer, said buffer layer forming a tunnel contact between the semiconductor layer and the collecting layer, and the buffer layer essentially made of a material with a negative surface charge density of at least 10 12 cm −2 ;
the buffer layer comprising a thickness ranging between 1 and 3 nm;
wherein the semiconductor layer adjacent to the buffer layer comprises a doping layer and/or an inversion layer or accumulation layer induced by means of the buffer layer, whereby the doping layer and/or inversion layer or accumulation layer is adjacent to the buffer layer; and
wherein the semiconductor layer is p-doped or the collecting layer comprises a semiconductor.
2. The solar cell according to claim 1 , wherein the buffer layer consists essentially of aluminium oxide.
3. The solar cell according to claim 1 , wherein the buffer layer is formed without pinholes.
4. The solar cell according to claim 1 , wherein the buffer layer has been applied by means of atomic layer deposition.
5. The solar cell according to claim 1 , wherein the semiconductor layer is made of a crystalline semiconductor.
6. The solar cell according to claim 1 , wherein the semiconductor layer is n-doped or p-doped.
7. The solar cell according to claim 1 , wherein the buffer layer is designed as an anti-reflection layer.
8. The solar cell according to claim 1 , wherein the collecting layer comprises a metal, a metal alloy and/or a transparent conductive material.
9. The solar cell according to claim 1 , wherein the collecting layer comprises a semiconductor.
10. The solar cell according to claim 9 , wherein the collecting layer comprises an amorphous semiconductor.
11. The solar cell according to claim 10 , wherein the collecting layer is n-doped or p-doped.
12. The solar cell according to claim 11 , wherein the collecting layer comprises a contact layer of a conductive material.
13. The solar cell according to claim 1 , wherein on a face of the semiconductor layer, which face points away from the buffer layer, a further buffer layer is provided between the semiconductor layer and a further collecting layer.
14. The solar cell of claim 1 wherein the buffer layer is essentially made of a material with a surface charge density of at least 5×10 12 cm −2 .
15. The solar cell of claim 1 wherein the buffer layer is essentially made of a material with a surface charge density of at least 10 13 cm −2 .