Optimization of Phosphorus Emitter Formation from POCl3 Diffusion for p-Type Silicon Solar Cells Processing

Abstract

The main purpose of this work is to demonstrate the possibility of diffusion process perfection during silicon solar cells manufacturing by CFD simulation. Presently, the major community of PV industries uses a p-type silicon solar cell as the starting material. In this work too, boron doped silicon wafers are considered to form solar cells. Likewise, phosphorus oxy-chloride (POCl3) is used as a precursor for phosphorus diffusion. To do this, we evaluate the throughput of an industrial low-pressure diffusion tube furnace in order to realize uniform emitters. The low-pressure tube furnace is designed to obtain emitter standard sheet resistances of about 60 Ω/sq and wafer uniformity less than 3 %. An up-to-date control model using for the first time a CFD numerical code has been derived from some previous work, to achieve better wafer to wafer temperature distribution. Moreover, a numerical process was built using an Atlas-Silvaco® TCAD Simulation Package where we can demonstrate that the short circuit current density (Isc) increases from 4.97 to 6.53 mA/cm2 compared to the conventional photovoltaic process. This (Isc) enhancement can be attributed to the strong temperature effect on furnace atmosphere. Our result proves that we can target electrical properties of an emitter only by the manipulation and optimization of the doping profile. This process refinement is expected to contribute in the development of high efficiency conventional crystalline silicon solar cells considered for mass production.