PassDop rear side passivation based on Al2O3/a-SiCx:B stacks for p-type PERL solar cells

Abstract

In this study we present a new approach for p-type PERL solar cells based on an Al2O3 passivation in combination with boron doped amorphous SiCx. During a laser diffusion process, the rear side passivation is locally opened and simultaneously dopants are driven from the stack into the silicon to create a local back surface field resulting in a sheet resistance in the range of 15Ω/sq. We show that the main contribution to the dopants in the local back surface field originates from the a-SiCx:B layer, while aluminum is mainly present near the surface. This p-type PassDop stack is compatible with a firing step, reaching surface recombination velocities lower than 3cm/s. With this stack, small area solar cells on p-type float-zone silicon were processed, achieving energy conversion efficiencies up to 21.4% and fill factors of up to 82.5% with PVD contacts in a proof-of-concept batch.