Investigation of p+ emitter formation for n-type silicon solar cells application

摘要： Investigation of p+ emitter formation for n-type silicon solar cells application. This work reports on the study of boron diffusion in n-type silicon from preform source for p+ emitter formation. Using quartz tube furnace, three main parameters are investigated that are: drive-in temperature, drive-in time and temperature ramp-up time. It is found that the sheet resistance as measured by the four point probe method (4-pp) decreases from 93 Ω/□ to 24 Ω/□ as the drive-in temperature increases from 850°C to 950°C, likewise, it decreases from 57 Ω/□ to 38 Ω/□ as the drive-in time increases from 20 min to 40 min. The electrically active boron dopant profiles as measured by the electrochemical capacitance voltage technique (ECV) exhibit surface concentrations below the solid-solubility limit of boron in silicon for all the studied emitters, the maximum surface and peak boron concentrations of 1.30x1020 and 1.58x1020 atoms/cm3 were measured respectively on the emitter which is formed at a drive-in temperature of 950°C. Furthermore, it is revealed from the secondary ion mass spectroscopy measurements (SIMS) the presence of the boron rich layer (BRL) on its surface. The Hall Effect measurement method is used for measuring sheet resistance and sheet charge carrier concentration.