SiOx n-LAYER FOR MICROCRYSTALLINE PIN JUNCTION
The present invention concerns a light conversion device comprising at least direction of impinging light one photovoltaic light conversion layer stack (43, 51) comprising a p-i-n junction and situated between a front (42) and back (47) electrode, wherein the n-layer (49) of the layer stack (43) situated closest to the back electrode (47) consists of a n-doped silicon- and oxygen-containing (SiOx) microcrystalline layer, and is in direct contact with the back electrode (47). The invention equally concerns a corresponding method for manufacturing such a light conversion device. The requirement for intermediate adhesion/interface layers between SiOx layer and back electrode can thus be obviated, resulting in simplified manufacture.
1 . Light conversion device comprising a front electrode and a back electrode, and at least one photovoltaic light conversion layer stack situated between said front and back electrodes, said layer stack comprising a p-doped silicon layer, an essentially intrinsic silicon layer, and an n-doped layer, said layers together forming a p-i-n junction, characterised in that the n-doped layer nearest to the back electrode is situated in direct and intimate contact with said back electrode and essentially consists of a silicon- and oxygen-containing doped microcrystalline material.
2 . Light conversion device according to claim 1 , wherein the said n-doped layer is further situated in direct and intimate contact with the essentially intrinsic silicon layer.
3 . Light conversion device according to claim 2 , wherein the n-doped layer is arranged so as to cause back side passivation of the adjacent intrinsic silicon layer.
4 . Light conversion device according to claim 1 , wherein the oxygen content of the n-doped layer is chosen such that the refractive index n of the n-doped layer at a wavelength of light of 500 nm is greater than or equal to 2.0.
5 . Light conversion device according to claim 1 , wherein the thickness of the n-doped layer is between 10-150 nm, preferably 20-50 nm.
6 . Solar cell or solar panel comprising a light conversion device according to claim 1 .
7 . Method for manufacturing a light conversion device comprising the steps of:
a) providing a transparent substrate;
b) providing a front electrode directly or indirectly on said substrate;
c) providing directly or indirectly on said front electrode at least one p-i-n junction of at least one photovoltaic light conversion layer stack, each conversion layer stack comprising a p-doped silicon layer, an essentially intrinsic silicon layer provided directly or indirectly on said p-doped silicon layer, and an n-doped layer provided directly or indirectly on said essentially intrinsic silicon layer,
d) providing a back electrode on the said n-doped layer situated furthest from the substrate,
characterised in that the back electrode is provided directly on the n-doped layer situated furthest from the substrate, and in that this n-doped layer consists essentially of a silicon- and oxygen-containing doped microcrystalline material.
8 . Method according to claim 7 , wherein the said n-doped layer is provided directly on the adjacent essentially intrinsic silicon layer.
9 . Method according to claim 7 , wherein the oxygen content of the said n-doped layer is chosen such that the refractive index n of the said n-doped layer at a wavelength of light of 500 nm is greater than or equal to 2.0.
10 . Method according to claim 7 , wherein the method is carried out by means of Plasma Enhanced Chemical Vapor Deposition PECVD in a corresponding PECVD plasma reactor.
11 . Method according claim 10 , wherein the said n-doped layer is applied on the intrinsic layer by applying a controlled backside passivation by plasma treatment.
12 . Method according to claim 10 , wherein the said n-doped layer is created by establishing in said PECVD plasma reactor a first plasma deposition regime with an overall process gas flow of substantially 0.3-1 sccm/cm 2 of substrate size to be treated, said process gas comprising silane, hydrogen and an n-dopant gas, said n-dopant gas preferably being 0.5% phosphine in hydrogen, the ratio of silane to n-dopant gas being between 1:1 and 1:5, and the ratio of silane to hydrogen being between 1:50 and 1:200, preferably 1:100.
13 . Method according to claim 12 , wherein the process pressure is chosen between 1.5 and 8 mbar, preferably 2.5-5 mbar, and an RF power of 150-200 mW/cm 2 , preferably 170-180 mW/cm 2 at a frequency of 13.56-60 MHz, preferably 40 MHz, is established in the PECVD reactor.
14 . Method according to claim 12 , wherein said first plasma regime is maintained for a time of 10-20 s, after which a flow of oxygen-comprising gas, preferably carbon dioxide, is additionally introduced, all other process parameters remaining the same, and whereby the flow ratio between silane and oxygen-containing gas is between 2:1 and 1:3, preferably between 1:1 and 1:2.