METHOD OF FORMING A PROTECTIVE LAYER ON THIN-FILM PHOTOVOLTAIC ARTICLES AND ARTICLES MADE WITH SUCH A LAYER
Chalcogenide based photovoltaic devices cells with good resistance to environmental elements can be formed by direct low temperature deposition of inorganic barrier layers onto the film. A unique multilayer barrier can be formed in a single step when reactive sputtering of the silicon nitride onto an inorganic oxide top layer of the PV device.
1 . A method of forming a photovoltaic article comprising:
providing at least one chalcogenide based photovoltaic cell, and
reactive sputtering inorganic barrier layer on the photovoltaic cell.
2 . The method of claim 1 wherein the inorganic barrier layer comprises a material having the formula SiO y N z , where y is less than 0.05 and z is greater than 1.1 and less than 1.4.
3 . The method of claim 2 wherein the inorganic barrier layer is sputtered onto a transparent conductive oxide layer which is on a top surface of the photovoltaic cell and an interstitial layer is formed between the transparent conductive oxide and the inorganic barrier layer during the reactive sputtering step.
4 . The method of claim 3 wherein the interstitial layer is a silicon oxynitride having a higher oxygen content than is found in the inorganic barrier layer.
5 . The method of claim 1 wherein the chalcogenide based photovoltaic cell comprises in order a backside substrate, a back electrical connector, a chalcogenide absorber, a buffer, a transparent conductive oxide, and an electrical collection grid.
6 . The method of claim 5 wherein the chalcogenide absorber is of the formula CuIn (1-x) Ga x Se (2-y) S y where x is 0 to 1 and y is 0 to 2.
7 . The method of claim 6 wherein the substrate is stainless steel, the back electrical connector is molybdenum, the buffer is cadmium sulfide, and the transparent conductive oxide is indium tin oxide or aluminum zinc oxide.
8 . The method of claim 1 wherein the sputtering step comprises sputtering a silicon target in the presence of nitrogen and argon gases where the mole ratio of nitrogen:argon is from 1:9 to 5:1 and the deposition occurs at temperatures of less than 100° C.
9 . The method of claim 1 wherein more than one chalcogenide cell is provided and the more than one cells are electrically connected prior to sputtering of the inorganic barrier.
10 . The method of claim 1 wherein more than one chalcogenide cell is provided further comprising electrically connecting the more than one cells after sputtering of the inorganic barrier.
11 . A method of forming a photovoltaic article comprising providing a chalcogenide based photovoltaic cell and direct depositing onto the cell at a deposition temperature of less than 200° C. an inorganic barrier to form a photovoltaic article that retains at least 85% of its initial efficiency after exposure for 85° C. and 85% relative humidity for a time of at least 1000 hours.
12 . The method of claim 11 wherein the deposition temperature is less than 100° C.
13 . The method of claim 11 wherein the deposition occurs via reactive sputtering.
14 . The method of claim 11 wherein the chalcogenide based photovoltaic cell comprises in order a substrate, a back electrical connector, a chalcogenide absorber, a buffer, a transparent conductive oxide, and an electrical collection grid.
15 . The method of claim 11 wherein the chalcogenide absorber is of the formula CuIn (1-x) Ga x Se (2-y) S y where x is 0 to 1 and y is 0 to 2.
16 . The method of any of claims 15 wherein the backside substrate is stainless steel, the back electrical connector is molybdenum, the buffer is cadmium sulfide, the transparent conductive oxide is indium tin oxide or aluminum zinc oxide.
17 . The method of claim 11 wherein the inorganic barrier is silicon nitride.
18 . The method of claim 11 wherein more than one chalcogenide cell is provided and the more than one cells are electrically connected prior to forming the inorganic barrier.
19 . The method of claim 11 wherein more than one chalcogenide cell is provided further comprising electrically connecting the more than one cells after forming the inorganic barrier.
20 . An article formed by the method of claim 1 .
21 . An article formed by the method of claim 11 .