DOUBLE LAYER ANTIREFLECTION COATING FOR SILICON BASED SOLAR CELL MODULES
A silicon wafer-based solar cell with a two-layer antireflective coating (ARC) combines a 10-30 nm thick hydrogen containing passivation layer (e.g. Si X N Y :H) with a top layer of Nb 2 O 5 (or Nb X O Y in general) for optimal matching the refractive index of the ARC to cover materials having a refractive index of about 1.5 (e.g. glass or EVA, Ethylene Vinyl Acetate). The two-layer ARC can be deposited either by PECVD or by reactive sputtering (PVD) of a Si target with N 2 and/or NH 3 , and the Nb 2 O 5 layer is deposited by reactive sputtering of either a pure Nb target or a conductive Nb 2 Ox (x<5) target with O 2 .
1 ) A silicon wafer-based solar cell with a two-layer antireflective coating comprising:
On a surface of a wafer-based silicon solar cell, said surface to be oriented to light during operation of said cell:
A hydrogen containing silicon passivation layer followed by
A niobium oxide Nb X O Y layer
A cover having a refractive index of about 1.5
2 ) A solar cell according to claim 1 , wherein the hydrogen containing silicon passivation layer is a hydrogenated silicon nitride Si X N Y :H layer.
3 ) A solar cell according to claim 1 , wherein the hydrogen containing silicon passivation layer has a thickness of 10-30 nm.
4 ) A solar cell according to claim 1 , wherein the niobium oxide essentially comprises Nb 2 O 5 .
5 ) A solar cell according to claim 1 , wherein the cover comprises glass or Ethylene Vinyl Acetate.
6 ) Method for manufacturing a silicon wafer-based solar cell with a two-layer antireflective coating, said method comprising:
Depositing a hydrogen containing silicon passivation layer on a surface of a wafer-based silicon solar cell, said surface to be oriented to light during operation of said cell;
followed by depositing a niobium oxide Nb X O Y layer;
and attaching a cover having a refractive index of about 1.5 onto said niobium oxide layer.
7 ) The method according to claim 6 , wherein the hydrogen containing silicon passivation layer is a hydrogenated silicon nitride Si X N Y :H layer.
8 ) The method according to claim 6 , wherein the niobium oxide essentially comprises Nb 2 O 5 .
9 ) The method according to claim 7 , wherein the Si x N y :H layer is deposited either by PECVD or by reactive sputtering (PVD) from a Si target with N 2 and/or NH 3 .
10 ) The method according to claim 8 , wherein the Nb 2 O 5 layer is deposited by reactive sputtering of either a pure Nb target or a conductive Nb 2 O x (x<5) target with O 2 .
11 ) The method according to claim 6 , wherein both layers of the two-layer antireflective coating are deposited subsequently in one single wafer multi chamber sputtering tool.
12 ) The method according to claim 8 , wherein the Nb 2 O 5 layer is deposited in a hydrogen containing gas atmosphere.