Screen-printable boron doping paste with simultaneous inhibition of phosphorus diffusion in co-diffusion processes

A printable boron doping paste or gel based on a precursor of silicon dioxide, aluminium oxide or boron oxide, comprising

• at least one polymer as thickener selected from the group consisting of polyvinylpyrrolidone, polyvinyl alcohol, polyvinyl acetate, polyvinylimidazole, polyvinylbutyral, methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, microcrystalline cellulose, sodium starch glycolate, xanthan gum, gellan gum, gelatine, agar, alginic acid, alginates, guar flour, pectin, carubin, polyacrylic acid, polyacrylate, associatively thickening polyurethane and a mixture thereof, which can be employed for local and/or full-area diffusion and doping on one side in solar cell production processes, and
• which paste or gel has been obtained from a precursor of silicon dioxide, aluminium oxide or boron oxide, or a mixture thereof,
• wherein
• the precursor of silicon dioxide is
• a symmetrically or asymmetrically mono- to tetrasubstituted carboxy-, alkoxy- or alkoxyalkylsilane, in which at least one hydrogen atom is bonded to the central silicon atom, or
• carboxy-, alkoxy- or alkoxyalkylsilane, which contain individual or different saturated, unsaturated branched, unbranched aliphatic, alicyclic or aromatic radicals, which are optionally functionalised at a position of the alkyl, alkoxide or carboxyl radical by one or more heteroatoms selected from the group consisting of O, N, S, Cl and Br, or
• tetraethyl orthosilicate, triethoxysilane, ethoxytrimethylsilane, dimethyldimethoxysilane, dimethyldiethoxysilane, triethoxyvinylsilane, bis[triethoxysilyl]ethane or bis[diethoxymethylsilyl]ethane,
• or a mixture thereof;
• the precursor of aluminum oxide is
• a symmetrically or asymmetrically substituted aluminium alcoholate (alkoxide), aluminium tris(β-diketone), aluminium tris(β-ketoester), an aluminium soap, an aluminium carboxylate, or
• aluminium triethanolate, aluminium triisopropylate, aluminium tri-sec-butylate, aluminium tributylate, aluminium triamylate, aluminium triisopentanolate, aluminium acetyl-acetonate or aluminium tris(1,3-cyclohexanedionate), aluminium monoacetylacetonate monoalcoholate, aluminium tris(hydroxyquinolate), mono- or dibasic aluminium stearate or aluminium triformate or aluminium trioctanoate, aluminium hydroxide, aluminium metahydroxide or aluminium trichloride,
• or a mixture thereof;
• the precursor of boron oxide is
• an alkyl borate, a boric acid ester of a functionalised 1,2-glycol, a boric acid ester of an alkanolamine, a mixed anhydride of boric acid or carboxylic acid, or
• boron oxide, diboron oxide, triethyl borate, triisopropyl borate, boric acid glycol ester, boric acid ethylene glycol ester, boric acid glycerol ester, boric acid ester of 2,3-dihydroxy-succinic acid, tetraacetoxy diborate and boric acid esters of the alkanolamines ethanolamine, diethanolamine, triethanolamine, propanolamine, dipropanolamine or tripropanolamine,
• or a mixture thereof.