Investigation of laser doping on the formation of selective emitter solar cells

Abstract

We investigated laser parameters for a laser doping (LD) process that enables to improve cell characteristics through the formation of a selective emitter (SE) multicrystalline silicon solar cell. In this work, the aim is the formation of SE with an investigation of the effect of critical LD parameters, such as laser power and laser speed. The LD 532 nm is used to obtain highly doped regions and deep doping depth that will receive the screen printed silver grid contact. The optimized laser power and speed of 80%, 500 mm/s, induced the activation of the phosphorus dopant and its diffusion in the silicon then leads to a local decrease of the emitter sheet resistance from 60 Ω/sqr to 30 Ω/sqr. Moreover, it was determined by SIMS and ECV measurements that the dopant concentration increased and the doping depth became deeper in the selective emitter formed by increasing laser power and/or laser speed. Fortunately, the surface cracks damage were not observed. The only damage caused by laser irradiation evidenced by debris and a melted surface. We have successfully developed SE p-type mc-Si 4 inch wafer produced by CRTSE solar cell with FF significantly improved of 1.01%. The conversion efficiency of solar cells with selective emitter formed by LD was increased. This gain is due to improved short-circuit current density and open-circuit voltage.