Influence of the organic solvents on the properties of the phosphoric acid dopant emulsion deposited on multicrystalline silicon wafers

This study is devoted to the formation of an n+p emitter for multicrystalline silicon (mc-Si) solar cells for photovoltaic (PV) application. The atomization technique has been used to make the emitter from H3PO4 phosphoric acid as a doping source. The doping emulsion has been optimized using several organic solvents. H3PO4 was mixed with one of these solutions: ethanol, 2-butanol, isopropanol alcohol and deionized water. The volume concentration of H3PO4 does not exceed 20% of the total volume emulsion. The deposit characteristics of the emulsion change with the organic solvent. H3PO4 : 2-butanol gives the best deposited layer with acceptable adherence and uniformity on silicon surface. Fourier transform infrared characterizations show the presence of organic and mineral phosphorous bonds in the formed layer. The obtained emitters are characterized by a junction depth in the range 0.2-0.75 mum and a sheet resistance of about 10-90 Omega/. Such a low cost dopant source combined with a continuous spray process can effectively reduce the cost per Wp of the PV generator.