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27th European Photovoltaic Solar Energy Conference and Exhibition; 1835-1837, In order to investigate and figure out the most promising phosphorus diffusion profile, two different approaches have been employed. The first one is based on previously reported 3-step process, in which another drivein step is performed after PSG removal. This method could effectively reduce the surface electrically inactive phosphorus and thus greatly improve Voc. However, the requirement of an extra process step, which causes narrower process window, might restrict the feasibility of mass production. Therefore, it inspires us to find out other replaceable methods to get the similar diffusion profiles as 3-step process. This newly developed novel one-step diffusion process can nearly meet the desired profiles without the requirement of an extra process step. Whichever method is applied, reduction of surface phosphorus concentration and deeper junction depth both contribute to an improvement of Voc. Therefore, it seems that shallow and abrupt diffusion profile might not be the optimal condition. Besides, with this novel one-step diffusion process, the plateau region of phosphorus profile can be tailored while the tail region is kept unchanged. So, the optimal surface phosphorus concentration, which has the least losses of minority carrier recombination and contact resistance, can be achieved.