FABRICATION OF TEXTURED SOLAR CELLS USING SPRAYED PHOSPHORIC ACID AS THE DOPANT SOURCE FOR THE IN-LINE EMITTER DIFFUSION

摘要

Solar cells were fabricated from textured boron-doped Cz-Si 125×125 mm~2 pseudo-square wafers with a bulk resistivity of 0.5-1.7 Ωcm or 3-6 Ωcm. The emitter was formed by spraying a solution consisting of 3% w/w phosphoric acid in DI water and of a small quantity of surfactant onto the wafer and by subsequent diffusion at 880℃ in a contamination-free in-line furnace. The contacts were formed using standard screen-printing and in-line fast firing. Sheet resistance R_(sh) was in the range of 38-43 Ω/sq and the cells yielded efficiencies of up to 17.5%. Fill factors of up to 79.1% indicate adequate emitter homogeneity on a microscopic scale. Some factors influencing R_(sh), homogeneity across a wafer were identified, such as the movement of the drying front of the sprayed layer. A R_(sh) variation of approx. ±3 Ω/sq was measured on 125×125 mm~2 pseudo-square wafers with an avg. R_(sh) of ～50 Ω/sq.