In this paper, the optimized doping condition of crystalline silicon solar cells with $156{ imes}156;mm^2$ area was studied. To optimize the drive-in temperature in the doping process, the other conditions except variable drive-in temperature were fixed. These conditions were obtained in previous studies. After etching$7;{mu}m$ of the surface to form the pyramidal structure, the silicon nitride deposited by the PECVD had 75~80nm thickness and 2 to 2.1 for a refractive index. The silver and aluminium electrodes for front and back sheet, respectively, were formed by screen-printing method, followed by firing in 400-425-450-550-$850^{circ}C$ five-zone temperature conditions to make the ohmic contact. Drive-in temperature was changed in range of $830^{circ}C$ to $890^{circ}C$to obtain the sheet resistance $30{sim}70;{Omega}/{ox}$ with $10;Omega}/{ox}$ intervals. Solar cell made in $890^{circ}C$ as the drive-in temperature revealed 17.1% conversion efficiency which is best in this study. This solar cells showed $34.4;mA/cm^2$ of the current density, 627 mV of the open circuit voltage and 79.3% of the fill factor.