Green-laser-doped selective emitters with separate BBr3 diffusion processes for high-efficiency n-type silicon solar cells

Abstract

Laser-doped boron selective emitters are an ideal candidate for enabling less emitter recombination, lower contact resistance and better blue response of efficient n-type silicon solar cells. However, the low boron concentration of the borosilicate glasses formed during boron diffusion processes and the implementation of ultraviolet lasers have hindered the commercialization of laser-doped boron selective emitters. In this contribution, separate BBr3 diffusion processes for green-laser-doped selective emitters are demonstrated. Laser doping processes were conducted between (1) borosilicate glass deposition and boron driving in and (2) post-oxidation, achieving the optimized laser doped selective emitter with the Rsheet,p+/Rsheet,p++ of 95.0 Ω/□/54.3 Ω/□, accompanying with the p+ profile of Nmax < 1.4× 1019 cm−3. By comparison to the homogeneous emitter with sheet resistance of 88.9 Ω/□, J0e, total of 45.3 fA/cm2 and ρc, metal of 2.9 mΩ/cm2, the employment of the optimum laser doped selective emitter has resulted in the J0e, total of 31.1 fA/cm2 and the ρc, metal of 1.0 mΩ/cm2. Finally, the improvement of simulated VOC (699.6 mV), FF (81.38%) and efficiency (23.13%) were obtained by using the optimized laser doped SEs, compared with the simulated VOC (694.5 mV), FF (81.14%) and efficiency (22.89%) of the reference. Separate BBr3 diffusion processes for green-laser-doped selective emitters demonstrate the employment of industrial green laser and boron diffusion furnace, instead of expensive ultraviolet laser and other complex boron resources, indicating a promising potential for industrial feasibility.