Detail: We use phosphorus as a donor impurity and make it diffuse into the P-type wafers to form the P-N junction. P-N Junction: Its function is absorption and conduction. In solar cell, the absorption of photonics occurs at P-type (N-type emitters are formed by lopading P-element POCL3 gas into P-type wafers.). Its important to have better absorption ratio and generate more conduction electrons of P-type layer. And reduce the combination of electrons and holes to extend the solar cell. (Lifetime is also another important) Factor:**If difusion of temperature, time, gas flow, post purge time it low the square resistance will be increased. And if opposite square resistance will be decrease. So Rs can reflect the concentration of impurities directly.