Efficiency Improvement of Industrial Silicon Solar Cells by the POCl₃ Diffusion Process

To improve the efficiency of polycrystalline silicon solar cells, process optimization is a key technology in the photovoltaic industry. Despite the efficiency of this technique to be reproducible, economic, and simple, it presents a major inconvenience to have a heavily doped region near the surface which induces a high minority carrier recombination. To limit this effect, an optimization of diffused phosphorous profiles is required. A "low-high-low" temperature step of the POCl₃ diffusion process was developed to improve the efficiency of industrial-type polycrystalline silicon solar cells. The low surface concentration of phosphorus doping of 4.54 × 10²⁰ atoms/cm³ and junction depth of 0.31 μm at a dopant concentration of N = 10¹⁷ atoms/cm³ were obtained. The open-circuit voltage and fill factor of solar cells increased up to 1 mV and 0.30%, compared with the online low-temperature diffusion process, respectively. The efficiency of solar cells and the power of PV cells were increased by 0.1% and 1 W, respectively. This POCl₃ diffusion process effectively improved the overall efficiency of industrial-type polycrystalline silicon solar cells in this solar field.