Current Photovoltaic Research ISSN:2288-3274(Print) 2508-125X(Online)

A boron doping process using a boron tri-bromide (BBr₃) as a boron source was applied to form a p ⁺ emitter layer on an n-type mono-crystalline CZ substrate. Nitrogen (N₂) gas as an additive of the diffusion process was varied in order to study the variations in sheet resistance and the uniformity of doped layer. The flow rate of N₂ gas flow was changed in the range 3 slm~10 slm. The sheet resistance uniformity however was found to be variable with the variation of the N₂ flow rate. The optimal flow rate for N₂ gas was found to be 4 slm, resulting in a sheet resistance value of 50 Ω/sq and having a uniformity of less than 10%. The process temperature was also varied in order to study its influence on the sheet resistance and minority carrier lifetimes. A higher lifetime value of 1727.72 μs was achieved for the emitter having 51.74 Ω/sq sheet resistances. The thickness of the boron rich layer (BRL) was found to increase with the increase in the process temperature and a decrease in the sheet resistance was observed with the increase in the process temperature. Furthermore, a passivated emitter solar cell (PESC) type solar cell structure comprised of a boron doped emitter and phosphorus doped back surface field (BSF) having Ni/Cu contacts yielding 15.32% efficiency is fabricated.