Passivated contacts to laser doped p⁺ and n⁺ regions

In this work, tunnel SiO₂/a-Si:H stacks are trialed as passivated contacts to laser doped p⁺ and n⁺ regions. The passivation performance and contact resistivity are investigated as a function of the tunnel SiO₂ thickness and annealing condition. We find that the SiO₂/a-Si:H stack provides excellent passivation to laser doped n⁺ regions, with corresponding low recombination current density (J_o) values. A lower level of surface passivation is achieved by the SiO₂/a-Si:H stack on laser doped p⁺ regions. A post-deposition forming gas anneal (FGA) at 400 °C is found to improve the passivation performance to laser doped p⁺ regions and deteriorate the passivation to laser doped n⁺ regions. Acceptable contact resistivity (ρ_c) values have been obtained for both laser doped n⁺ and p⁺ regions after aluminum metallization and a post FGA to activate the alloying process between the a-Si:H and aluminum layer. In the final part of this work implementation of the passivated contacts to laser doped regions into a simplified interdigitated back-contact (IBC) solar cell fabrication process is proposed. Simulation result suggests that IBC device with an efficiency of up to 23% can be achieved using the obtained experimental results.