Methods and compositions for the formation of recessed electrical features on a substrate
Precursor compositions having a low conversion temperature and methods for the fabrication of recessed electrical features from the precursor compositions. The electrical features can be conductors, resistors and dielectric features. The precursor compositions are deposited into recessed features, such as trenches, formed in a substrate and are reacted at a low temperature to form electrical features having good electrical and mechanical properties. The substrate can be a low temperature substrate, such as an organic substrate.
1 . A process for forming a solar cell conductive feature, comprising:
(a) direct printing a precursor composition comprising at least one of metallic particles comprising a metal or a metal precursor compound to the metal; and
(B) heating the precursor composition to form the solar cell conductive feature on the substrate, wherein the solar cell conductive feature has a feature width of not greater than 200 μm, a thickness greater than about 2 μm, and a conductivity that is no less than 10 percent the conductivity of the equivalent pure metal.
2 . The process of claim 1 , wherein the direct printing comprises syringe printing.
3 . The process of claim 1 , wherein the direct printing comprises aerosol printing.
4 . The process of claim 1 , wherein the direct printing comprises ink jet printing.
5 . The process of claim 4 , wherein the thickness is greater than about 5 μm.
6 . The process of claim 4 , wherein the thickness is greater than about 10 μm.
7 . The process of claim 4 , wherein the thickness is greater than about 25 μm.
8 . The process of claim 4 , wherein the conductive feature has an aspect ratio of less than 1:1.
9 . The process of claim 4 , wherein the conductive feature has an aspect ratio of up to 20:1.
10 . The process of claim 4 , wherein the precursor composition has a viscosity not greater than 20 centipoise.
11 . The process of claim 4 , wherein the precursor composition further comprises metal oxide particles.
12 . The process of claim 4 , wherein the precursor composition further comprises glass particles.
13 . The process of claim 4 , wherein the precursor composition further comprises lead borosilicate glass.
14 . The process of claim 4 , wherein the precursor composition further comprises a low melting glass.
15 . The process of claim 4 , wherein the conductive feature has a resistivity that is not greater than 4 times the resistivity of the equivalent pure metal.
16 . The process of claim 4 , wherein the conductive feature has a resistivity that is not greater than 2 times the resistivity of the equivalent pure metal.
17 . The process of claim 4 , wherein the heating comprises heating the precursor composition to a temperature not greater than 300° C. to form the solar cell conductive feature on the substrate.
18 . The process of claim 4 , wherein the heating comprises heating the precursor composition to a temperature not greater than 225° C. to form the solar cell conductive feature on the substrate.
19 . The process of claim 4 , wherein the heating comprises heating the precursor composition to a temperature not greater than 185° C. to form the solar cell conductive feature on the substrate.
20 . The process of claim 4 , wherein the substrate has a softening point of not greater than about 225° C.
21 . The process of claim 4 , wherein the substrate comprises a ceramic.
22 . The process of claim 4 , wherein the substrate comprises a polymer.
23 . The process of claim 4 , wherein the precursor composition comprises the metal precursor compound to the metal.
24 . The process of claim 23 , wherein the metal is selected from the group consisting of silver, palladium, copper, gold, platinum and nickel.
25 . The process of claim 4 , wherein the precursor composition comprises the metallic particles comprising the metal
26 . The process of claim 25 , wherein the heating sinters adjacent particles to one another.
27 . The process of claim 25 , wherein the metal is selected from the group consisting of silver, palladium, copper, gold, platinum and nickel.
28 . The process of claim 25 , wherein the metallic particles have a volume median particle size of not greater than 100 nanometers.
29 . The process of claim 25 , wherein the metallic particles have a volume median particle size of not greater than 0.3 μm.
30 . The process of claim 29 , wherein the metallic particles comprise a cap or coating thereon.
31 . The process of claim 30 , wherein the cap or coating comprises an inorganic cap or coating.
32 . The process of claim 30 , wherein the cap or coating comprises silica.
33 . The process of claim 30 , wherein the cap or coating comprises an organic cap or coating.
34 . The process of claim 30 , wherein the cap or coating comprises a polymer.
35 . The process of claim 30 , wherein the cap or coating comprises an intrinsically conductive polymer, a sulfonated perfluorohydrocarbon polymer, polystyrene, polystyrene/methacrylate, sodium bis(2-ethylhexyl)sulfosuccinate, tetra-n-octyl-ammonium bromide or an alkane thiolate.
36 . The process of claim 30 , wherein the cap or coating comprises PVP.
37 . The process of claim 4 , wherein the conductive feature comprises a set of finger lines and collector lines deposited essentially at a right angle to the finger lines.
38 . The process of claim 37 , wherein either or both the parallel finger lines or the collector lines have width less than 200 μm.
39 . The process of claim 37 , wherein either or both the parallel finger lines or the collector lines have width less than 100 μm.
40 . The process of claim 4 , wherein the conductive feature comprises a transparent conductive feature.
41 . The process of claim 4 , wherein the conductive feature comprises indium-tin oxide or antimony-tin oxide.
42 . The process of claim 4 , wherein the conductive feature comprises a metal-glass composition.
43 . The process of claim 4 , wherein the conductive feature is resistant to solder leaching.
44 . The process of claim 4 , wherein the process further comprises high shear mixing the precursor composition.
45 . The process of claim 4 , wherein the process further comprises surface modifying the substrate with a laser.