Antireflective coatings for photovoltaic applications

1. A process for making a photovoltaic device comprising a silicon substrate comprising a p-n junction, the process comprising the steps of:

forming an amorphous silicon carbide antireflective coating over at least one surface of the silicon substrate by chemical vapor deposition of a composition comprising a precursor selected from the group consisting of

(a) cyclic silazane compounds of the formula (NR 1 SiR 1 R 3 ) x , where R 1 and R 3 are independently H, C 1 to C 4 , linear or branched, saturated, singly or multiply unsaturated, cyclic, partially or fully fluorinated; and x is an integer from 2 to 8;

(b) cyclic carbosilane compounds of the formula (CR 1 R 3 SiR 1 R 3 ) x , where R 1 and R 3 are independently H, C 1 to C 4 , linear or branched, saturated, singly or multiply unsaturated, cyclic, partially or fully fluorinated; and x is an integer from 2 to 8;

(c) non-cyclic alkyl silanes of the formula (R 1n R 2m R 3o R 4p )Si—H 4-t , where R 1 to R 4 can be C 1 to C 4 linear or branched, saturated, singly or multiply unsaturated, cyclic, partially or fully fluorinated; and t=n+m+o+p and t=1 to 4;

(d) compounds of the formula R 1 n (NR 2 ) 4-n Si, where R 1 is independently H or C 1 to C 4 linear or branched, saturated, singly or multiply unsaturated, cyclic, partially or fully fluorinated hydrocarbon; R 2 is independently C 1 to C 6 linear or branched, saturated, singly or multiply unsaturated, cyclic, aromatic, partially or fully fluorinated hydrocarbon; and n is 0 to 3;

(e) compounds of the formula R 1 n (NR 2 ) 3-n Si—SiR 3 m (NR 4 ) 3-m where R 1 and R 3 are independently H or C 1 to C 4 linear or branched, saturated, singly or multiply unsaturated, cyclic, partially or fully fluorinated hydrocarbon; R 2 and R 4 are independently C 1 to C 6 linear or branched, saturated, singly or multiply unsaturated, cyclic, aromatic, partially or fully fluorinated hydrocarbon; and n is 0 to 3, m is 0 to 3;

(f) compounds of the formula R 1 n (NR 2 ) 3-n Si—R 5 —SiR 3 m (NR 4 ) m-3 where R 1 and R 3 are independently H or C 1 to C 4 linear or branched, saturated, singly or multiply unsaturated, cyclic, partially or fully fluorinated hydrocarbon; R 2 , R 4 and R 5 are independently C 1 to C 6 linear or branched, saturated, singly or multiply unsaturated, cyclic, aromatic, partially or fully fluorinated hydrocarbon, alternatively, R 5 is an amine or an organoamine group; n is 0 to 3; and m is 0 to 3;

(g) compounds of the formula (R 1 n (NR 2 ) 3-n Si) t CH 4-t where R 1 is independently H or C 1 to C 4 linear or branched, saturated, singly or multiply unsaturated, cyclic, partially or fully fluorinated hydrocarbon; R 2 is independently C 1 to C 6 linear or branched, saturated, singly or multiply unsaturated, cyclic, aromatic, partially or fully fluorinated hydrocarbon; n is 0 to 3; and t is 1 to 3;

(h) bis(tertiarybutylamino)silane; and mixtures thereof;

wherein

the amorphous silicon carbide antireflective coating is a film formed without ammonia or N 2 and represented by the formula Si v C x N u H y F z , wherein v+x+u+y+z=100%, v is from 1 to 35 atomic %, x is from 5 to 80 atomic %, u is from 0 to 50 atomic %, y is from 10 to 50 atomic % and z is from 0 to 15 atomic %.

2. The process of claim 1 wherein the substrate is texturized.

3. The process of claim 1 wherein the composition further comprises a hydrocarbon.

4. The process of claim 1 wherein the aminosilane is bis(tertiarybutylamino)silane.

5. The process of claim 3 wherein the hydrocarbon is distinct from the precursor.

6. The process of claim 1 wherein the precursor is at least one non-cyclic alkyl silane of the formula (R 1n R 2m R 3o R 4p )Si—H 4-t , where R 1 -R 4 can be C 1 to C 4 linear or branched, saturated, singly or multiply unsaturated, cyclic, partially or fully fluorinated; and t=n+m+o+p and t=1 to 4.

7. The process of claim 6 wherein the precursor is selected from the group consisting of: monomethylsilane, dimethylsilane, trimethylsilane, and tetramethylsilane.

8. The process of claim 7 wherein the precursor is tetramethylsilane.

9. The process of claim 3 wherein the hydrocarbon is selected from the group consisting of:

1) cyclic hydrocarbons of the general formula C n H 2n where n=4-14, wherein the number of carbons in the cyclic structure is between 4 and 12;

2) linear or branched, saturated, singly or multiply unsaturated hydrocarbons of the general formula C n H (2n+2)-2y , where n=2-20 and where y=units of unsaturation;

3) singly or multiply unsaturated cyclic hydrocarbons of the general formula C n H 2n-2x , where x is the number of unsaturated sites in the hydrocarbon molecule; and n=4-14, where the number of carbons in the cyclic structure is between 4 and 10;

4) bicyclic hydrocarbons of the general formula C n H 2n-2 , where n=4-14, and where the number of carbons in the bicyclic structure is between 4 and 12;

5) multiply unsaturated bicyclic hydrocarbons of the general formula C n H 2n-(2+2x) , where x is the number of unsaturated sites in the molecule; and n=4-14, and where the number of carbons in the bicyclic structure is between 4 and 12; and

6) tricyclic hydrocarbons of the general formula C n H 2n-4 where n=4-14, and where the number of carbons in the tricyclic structure is between 4 and 12.

10. The process of claim 9 wherein the hydrocarbon is selected from the group consisting of: cyclohexane, trimethylcyclohexane, 1-methyl-4(1-methylethyl)cyclohexane, cyclooctane, methylcyclooctane, cyclooctene, cyclooctadiene, cycloheptene, cyclopentene, cyclohexene, 1,5,9-cyclododecatriene, ethylene, propylene, acetylene, neohexane, cyclohexene, vinylcyclohexane, dimethylcyclohexene, t-butylcyclohexene, alpha-terpinene, pinene, 1,5-dimethyl-1,5-cyclooctadiene, vinyl-cyclohexene, norbornane, spiro-nonane, decahydronaphthalene, camphene, norbornene, norbornadiene, and adamantane.