p-Doped silicon layers
View Patent ↗The invention relates to a process for producing p-doped silicon layers, especially those silicon layers which are produced from liquid silane-containing formulations. The invention further relates to a substrate coated with a p-doped silicon layer. The invention additionally relates to the use of particular dopants based on boron compounds for p-doping of a silicon layer.
1. A process for producing a p-doped silicon layer arranged on a substrate, the process comprising:
(a) applying a formulation to a substrate to obtain a coated substrate, wherein the formulation comprises:
a silicon compound, and
a BH 3 complex comprising BH 3 and a complexing agent selected from the group consisting of THF; NR 3 wherein R═H, alkyl, or aryl; and SR′ 2 wherein R′═H, alkyl, or aryl,
wherein the silicon compound and the BH 3 complex are separate components in the formulation,
and
(b) irradiating, thermally treating, or both irradiating and thermally treating the coated substrate to form a p-doped silicon layer.
2. The process according to claim 1 , wherein the silicon compound is
a silicon-hydrogen compound;
a silicon halide;
a silicon organyl;
an oligomeric silicon compound Si n R 2n+2 or Si n R 2n , wherein n=8 to 100 and each R is independently selected from the group consisting of H, a halogen, and an organyl; or
any mixture thereof.
3. The process according to claim 2 , wherein
the silicon compound is a partly or wholly oligomerized silicon compound, and
a molar mass of the oligomerized silicon compound is from 330 g/mol to 10 000 g/mol.
4. The process according to claim 1 , wherein the formulation further comprises a solvent.
5. The process according to claim 1 , wherein the substrate is coated by flexographic/gravure printing, inkjet printing, offset printing, digital offset printing, screen printing, a spraying process, a rotary coating process, a dipping process, or a process selected from the group consisting of a meniscus coating, a slit coating, a slot-die coating and a curtain coating.
6. The process according to claim 1 , wherein the thermally treating is performed at a temperature of from 200 to 1000° C.
7. The process according to claim 1 , wherein the applying and the irradiating, thermally treating or both are performed more than once.
8. The process according to claim 1 , wherein the substrate is electrically conductive or comprises an electrically conductive surface.
9. The coated substrate produced by the process according to claim 1 .
10. A photovoltaic unit produced by the process according to claim 1 .
11. A p-doped silicon layer produced by the process according to claim 1 .
12. The process according to claim 1 , wherein the silicon compound is a silicon-hydrogen compound of a general formula of Si n H 2n+2 or Si n H 2n , wherein n=3 to 20.
13. The process according to claim 3 , wherein the molar mass of the oligomerized silicon compound is from 400 g/mol to 3000 g/mol.
14. The process according to claim 3 , wherein the molar mass of the oligomerized silicon compound is from 500 g/mol to 1000 g/mol.
15. The process according to claim 1 , wherein the thermally treating is performed at a temperature of from 250 to 700° C.
16. The process according to claim 1 , wherein the thermally treating is performed at a temperature of from 300 to 650° C.
17. The process according to claim 1 , wherein:
the silicon compound is cyclopentasilane,
the BH 3 complex comprises BH 3 and THF, and
the process comprises thermally treating the coated substrate to form a p-doped silicon layer.
18. The process according to claim 17 , wherein a specific dark resistivity of the p-doped silicon layer is at most 2×10 5 ohm-cm.