Precursors for Photovoltaic Passivation
Deposition methods are disclosed for producing a passivation layer on a photovoltaic cell. Method includes depositing a passivation layer comprising at least a bi-layer further comprising a silicon oxide and a silicon nitride layer. In one aspect, the silicon precursor(s) used for the deposition of the silicon oxide layer or the silicon nitride layer, respectively, is selected from the family SiR x H y or selected from the family SiR x H, silane, and combinations thereof, wherein in SiR x H y x+y=4, y≠4 and R may be independently selected from the group consisting of C 1 -C 8 linear alkyl, wherein the ligand may be saturated or unsaturated; C 1 -C 8 branched alkyl, wherein the ligand may be saturated or unsaturated; C 1 -C 8 cyclic alkyl, wherein the ligand may be saturated, unsaturated, or aromatic; and NR* 3 wherein R* can be independently hydrogen; or linear, branched, cyclic, saturated, or unsaturated alkyl. Photovoltaic devices containing the passivation layers are also disclosed.
1 . A method for depositing at least one passivation layer on a photovoltaic cell in a chamber comprising steps of:
providing the photovoltaic cell having a rear surface and a front surface;
providing a first silicon precursor;
providing an oxygen source;
depositing a silicon oxide layer having a thickness ranging from 5 to 70 nm at least on one surface of the photovoltaic cell;
providing a second silicon precursor;
providing a nitrogen source; and
depositing a silicon nitride layer having a thickness ranging from 20 to 200 nm on the silicon oxide layer;
wherein the passivation layer having a thickness ranging from 25 to 600 nm comprising at least one bi-layer comprising the silicon oxide layer and the silicon nitride layer.
2 . The method of claim 1 , wherein
the first silicon precursor is selected from family of SiR x H y ; and
the second silicon precursor is selected from silane, the family of SiR x H y , and combinations thereof;
wherein x+y=4, y≠4, and
R is independently selected from the group consisting of
C1-C8 linear alkyl, wherein the ligand is saturated or unsaturated;
C1-C8 branched alkyl, wherein the ligand may be saturated or unsaturated;
C1-C8 cyclic alkyl, wherein the ligand may be saturated, unsaturated, or aromatic; and
NR* 3 ;
wherein R* can be independently selected from the group consisting of hydrogen; and linear, branched, cyclic, saturated, or unsaturated alkyl;
3 . The method of claim 2 , wherein
the C1-C8 linear alkyl is selected from the group consisting of methyl, ethyl, butyl, propyl, hexyl, ethylene, vinyl, allyl, 1-butylene, and 2-butylene;
the C1-C8 branched alkyl is selected from the group consisting of isopropyl, isopropylene, isobutyl, and tert-butyl;
the C1-C8 cyclic alkyl is selected from the group consisting of cyclopentyl, cyclohexyl, benzyl, and methylcyclopentyl.
4 . The method of claim 1 , wherein the family of SiR x H y is selected from the group consisting of: methylsilane, dimethylsilane, trimethylsilane, tetramethylsilane, ethylsilane, diethylsilane, tetraethylsilane, propylsilane, dipropylsilane, isobutylsilane, tertbutylsilane, dibutylsilane, methylethylsilane, dimethyldiethylsilane, methyltriethylsilane, ethyltrimethylsilane, isopropylsilane, diisopropylsilane, triisopropylsilane, disopropylaminosilane, aminosilane, diaminosilane, methylaminosilane, ethylaminosilane, diethylaminosilane, dimethylaminosilane, bis-tertbutylaminosilane, and bis-isopropylamino(methylvinylsilane); and combinations thereof.
5 . The method of claim 1 , wherein the first silicon precursor is tetramethyl silane and the second silicon precursor is trimethyl silane.
6 . The method of claim 1 , wherein the first silicon precursor and the second silicon precursor are the same.
7 . The method of claim 5 , wherein the first silicon precursor and the second silicon precursor are both triethylsilane.
8 . The method of claim 1 wherein the oxygen source is selected from the group consisting of O 2 , N 2 O, ozone, hydrogen peroxide, NO, NO 2 , N 2 O 4 , and mixtures thereof; and the nitrogen source is selected from the group consisting of ammonia, methylamine, dimethylamine, trimethylamine, and mixtures thereof.
9 . The method of claim 1 , wherein depositing method is chemical vapor deposition or plasma enhanced chemical vapor deposition.
10 . The method of claim 1 , wherein the oxygen source and the nitrogen source flowing at a rate independently from 500 to 10,000 sccm into the chamber; the first silicon precursor and the second silicon precursor flowing at a rate independently from 10 sccm to 1700 sccm into the chamber
11 . The method of claim 1 , wherein the silicon oxide layer is deposited at a temperature between 200 and 400° C.; and the silicon nitride layer is deposited at a temperature between 300° C. and 450° C.
12 . The method of claim 1 , wherein the passivation layer has a surface recombination velocity <200 cm/s.
13 . The method of claim 1 , wherein the passivation layer has a surface recombination velocity <100 cm/s.
14 . The method of claim 1 further comprising a step of heat treating the passivation layer at 800 to 950° C. for 1-10 seconds.
15 . The method of claim 1 , wherein the silicon oxide layer having a thickness ranging from 5 to 45 nm; and the silicon nitride layer having a thickness ranging from 30 to 150 nm.
16 . A photovoltaic device comprising:
a photovoltaic cell comprising:
a P-doped silicon layer adjacent a N-doped silicon layer,
a rear surface and a front surface;
and
at least one passivation layer deposited on the photovoltaic cell by the method of claim 1 .
17 . A photovoltaic device comprising:
a photovoltaic cell comprising
a P-doped silicon layer adjacent a N-doped silicon layer,
a rear surface and a front surface;
and
at least one passivation layer having a thickness ranging from 25 to 600 nm deposited on at least one of the surfaces of the photovoltaic cell;
wherein the passivation layer having at least one bi-layer consisting of a silicon oxide layer having a thickness ranging from 5 to 70 nm and a silicon nitride layer having a thickness ranging from 20 to 200 nm.
18 . The photovoltaic device of claim 17 , wherein the passivation layer has a surface recombination velocity <200 cm/s.
19 . The photovoltaic device of claim 17 , wherein the passivation layer has a surface recombination velocity <100 cm/s.
20 . The photovoltaic device of claim 17 , wherein the silicon oxide layer having a thickness ranging from 5 to 45 nm; and the silicon nitride layer having a thickness ranging from 30 to 150 nm.