Influence of IR laser doping method on surface emitter with phosphosilicate glass for solar cells

Abstract

Laser-assisted diffusion of phosphorus dopants has been investigated to realize selective emitters on mc-Si wafers. In this paper, we studied, in the presence of PSG, the effect of laser speed and power doping parameters on the sheet resistance R _Sq variation as a function of selective emitter formation. Four point-probe (FPP) measurements showed that 5.5–10 W with speed 100–1500 mm s ^−1 are, respectively, the best power values to form a selective emitter with 20–40 Ω/□ typical values. Electrochemical Capacitance-Voltage (ECV) results showed that dopant concentration and junction depth increased with decreasing scan speed, resulting in lower sheet resistances. Thus, the greater the difference between the concentration of starting phosphorus and that created by laser treatment, the smaller the square R _Sq will be. Scanning Electron Microscopy (SEM) images demonstrated more pronounced patterns of laser ablation when the power is high and/or the scanning speed is low.

Keywords

• solar cells
• selective emitter
• laser doping
• PSG