IBC c-Si(n) Solar Cells Based on Laser Doping Processing for Selective Emitter and Base Contact Formation

Abstract

In the last years, there is a clear trend in c-Si solar cell fabrication to place both emitter and base contacts on the back side leading to the so-called Interdigitated Back Contacted (IBC) solar cell structure. This solar cell architecture requires excellent front and rear surface passivation as well as a very low recombination emitter. Moreover, laser doping may be an attractive technique to create both selective emitter and base contacts using appropriate dielectric layers as dopant sources, i.e. Al2O3 and a-SiCx(n) stacks for the p+ and n+ regions respectively. In this study, we report on a simplified fabrication process for IBC n-type c-Si solar cells combining laser doping and a conventional boron emitter passivated by Al2O3 films. Results show very low emitter recombination currents in the ∼10-50 fA/cm2 range before laser processing. In addition, selective emitter contacts can be created by laser doping with recombination current densities at each contact point around 4.4 pA/cm2 in relatively low and shallow doped boron doped profiles (sheet resistance ∼400Ω/sq). Finally, IBC solar cells, 3 x 3 cm2 device area, were fabricated combining selective laser-doped emitter and base contacts reaching efficiencies up to 20.8%.