Passivated contacts to laser doped p+ and n+ regions

Abstract

In this work, tunnel SiO2/a-Si:H stacks are trialed as passivated contacts to laser doped pþ and nþ 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 nþ regions, with corresponding low recombination current density (Jo) values. A lower level of surface passivation is achieved by the SiO2/a-Si:H stack on laser doped pþ regions. A postdeposition forming gas anneal (FGA) at 400 °C is found to improve the passivation performance to laser doped pþ regions and deteriorate the passivation to laser doped nþ regions. Acceptable contact resistivity (ρc) values have been obtained for both laser doped nþ and pþ 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.