Surface cleaning and texturing process for crystalline solar cells

Abstract

Methods for surface texturing a crystalline silicon substrate are provided. In one embodiment, the method includes providing a crystalline silicon substrate, wetting the substrate with an alkaline solution comprising a wetting agent, and forming a textured surface with a structure having a depth about 1 μm to about 10 μm on the substrate. In another embodiment, a method of performing a substrate texture process includes providing crystalline silicon substrate, pre-cleaning the substrate in a HF aqueous solution, wetting the substrate with a KOH aqueous solution comprising polyethylene glycol (PEG) compound, and forming a textured surface with a structure having a depth about 3 μm to about 8 μm on the substrate.

1 . An etching solution for forming a texture on a solar cell substrate, comprising:
 an alkaline solution comprising an etching additive that comprises a phenol or a derivative thereof.   
     
     
         2 . The etching solution of  claim 1 , wherein the phenol or the derivative thereof comprises poly(4-vinyl phenol), brominated poly(4-vinyl phenol), polystyrine sulphonic acid, Joncryl® polymers or derivatives thereof. 
     
     
         3 . The etching solution of  claim 1 , wherein the phenol or the derivative thereof comprises an ortho-cresol, a meta-cresol, a para-cresol, a poly(cresol) or derivatives thereof. 
     
     
         4 . The etching solution of  claim 1 , wherein the phenol or the derivative thereof comprises poly(4-vinyl phenol) or derivatives thereof. 
     
     
         5 . The etching solution of  claim 1 , further comprising:
 a wetting agent that is selected from a group consisting of polyethylene glycol (PEG), sodium dodecyl sulfate (SDS), polypropylene glycol (PPG), copolymer of polyethylene glycol (PEG) and polypropylene glycol (PPG).   
     
     
         6 . The etching solution of  claim 1 , wherein the alkaline solution further comprises an isopropyl alcohol free aqueous solution. 
     
     
         7 . The etching solution of  claim 6 , wherein the alkaline solution further comprises potassium hydroxide, sodium hydroxide, aqueous ammonia or tetramethylammonium hydroxide. 
     
     
         8 . An etching solution for forming a texture on a silicon containing solar cell substrate, comprising:
 an alkaline solution comprising a wetting agent that comprises a polyether or a non-ionic surfactant, and an etching additive that comprises a phenol or a derivative thereof.   
     
     
         9 . The etching solution of  claim 8 , wherein
 the wetting agent further comprises polyethylene glycol (PEG), sodium dodecyl sulfate (SDS), polypropylene glycol (PPG), copolymer of polyethylene glycol (PEG) or polypropylene glycol (PPG), and   the etching additive further comprises poly(4-vinylphenol) (PVP), brominated poly(4-vinyl phenol), polystyrine sulphonic acid (PSSA), Joncryl® polymers, phenol, ortho-cresol, meta-cresol, para-cresol or poly(cresol).   
     
     
         10 . The etching solution of  claim 8 , wherein the wetting agent comprises polyethylene glycol that has a molecular weight between about 20 and about 50,000. 
     
     
         11 . The etching solution of  claim 8 , wherein the alkaline solution further comprises an isopropyl alcohol free aqueous solution. 
     
     
         12 . The etching solution of  claim 11 , wherein the alkaline solution further comprises potassium hydroxide, sodium hydroxide, aqueous ammonia or tetramethylammonium hydroxide. 
     
     
         13 . An etching solution for forming a texture on a silicon containing solar cell substrate, comprising:
 an alkaline solution comprising:
 a polyethylene glycol (PEG) compound having a molecular weight between about 200 and about 8000, wherein the concentration of the polyethylene glycol (PEG) compound in the alkaline solution is between about 50 ppm and about 20,000 ppm; and 
 an etching additive that comprises a phenol or a derivative thereof. 
   
     
     
         14 . The etching solution of  claim 13 , wherein the etching additive comprises poly(4-vinyl phenol) or derivatives thereof in a concentration of between about 50 and about 4,000 ppm. 
     
     
         15 . The etching solution of  claim 13 , wherein the alkaline solution further comprises potassium hydroxide, sodium hydroxide, aqueous ammonia or tetramethylammonium hydroxide. 
     
     
         16 . An etching solution for forming a texture on a silicon containing solar cell substrate, comprising:
 an alkaline solution comprising a poly(4-vinyl phenol) or derivatives thereof, in a concentration of between about 50 and about 4,000 ppm.   
     
     
         17 . The etching solution of  claim 16 , wherein the alkaline solution further comprises an isopropyl alcohol free aqueous solution. 
     
     
         18 . An etching solution for forming a texture on a silicon containing solar cell substrate, comprising:
 an alkaline solution comprising:
 a polycresol or derivatives thereof; and 
 a chemical selected from a group consisting of potassium hydroxide, sodium hydroxide, aqueous ammonia and tetramethylammonium hydroxide. 
   
     
     
         19 . The etching solution of  claim 18 , wherein the alkaline solution further comprises an isopropyl alcohol free aqueous solution. 
     
     
         20 . An etching solution for forming a texture on a crystalline solar cell substrate, comprising:
 a potassium hydroxide in a concentration of between about 1 and about 15 percent by weight;   a polyethylene glycol (PEG) compound having a molecular weight between about 200 and about 8000, wherein the concentration of the polyethylene glycol (PEG) compound in the etching solution is between about 200 ppm and about 500 ppm; and   an etching additive that comprises a poly(4-vinyl phenol), a polycresol or derivatives thereof.   
     
     
         21 . The etching solution of  claim 20 , wherein the alkaline solution further comprises an isopropyl alcohol free aqueous solution. 
     
     
         22 . The etching solution of  claim 20 , wherein the concentration of the poly(4-vinyl phenol) or derivatives thereof is between about 50 and about 4,000 ppm.