Experimental study of boric acid diffused emitters for n-type c-Si solar cells

In this work, boric acid powder solution has been used as a dopant source for optimizing emitter sheet resistance values corresponding to temperature range 850°-900°C. High purity (99.999%), non-toxic and low-cost boron diffusion is found to be suitable for p or p⁺ emitters with minimum diffusion-induced defects. Formation of a boron-rich layer, which is considered as a major problem in B-diffusion is eliminated with introduction of controlled process steps. An increase of effective minority carrier lifetime is observed after the diffusion process. The measured Sun´s V_oc and Implied V_oc for sheet resistances less than 100Ω/sq is in the range of 570-600 mV, without any optics-improving techniques, for Czochralski n-type c-Si wafers. This indicates the suitability of the use of boric acid as the dopant source for emitter formation in n-type c-Si solar cells.