The high cost of crystalline silicon solar cells has been considered as one of the major obstacles to their terrestrial applications. Spin on doping (SOD) is presented as a useful process for the manufacturing of low cost solar cells. Phosphorus (P509) was used as an n-type emitters of solar cells. N-type emitters were formed on p-type EFG ribbon Si wafers by using a SOD at different spin speed (1,000~4,000 rpm), diffusion temperatures ($800^{circ}C{sim}950^{circ}C$), and diffusion time (5~30 min) in $N_2+O_2$ atmosphere. With optimum condition, we were able to achieve cell efficiency of 14.1%.