Screen printed boron emitters for solar cells

Screen printed (SP) boron emitters are presented as a useful option for the manufacturing of p-type emitters of solar cells. Details are provided on the diffusion process, including deposition, drying and firing steps, the latter performed in an infrared belt furnace. Besides their main dependences on the firing conditions, the sheet resistances and dopant profiles of the resulting emitters reveal the relevance of the drying step and the exhaustion limits of the doping source. A characterization of the recombination concludes that moderate emitter saturation currents (J(oe) < 0. 5 pA/cm(2)) and acceptable bulk lifetimes (tau(B) > 40 mu s) can be obtained on Czochralski silicon wafers. Finally, Cz n-type 0.7 Omega cm solar cells are presented, which once again prove the feasibility of SP boron emitters and point to issues regarding their metallization. (C) 2007 Elsevier B.V. All rights reserved.