Modification on electrical characteristics of interface states by using nitrogen and phosphorus co-doped polysilicon in tunnel oxide passivation contact silicon solar cells

The influence on electrical characteristics of interface states by using nitrogen (N) and phosphorus (P) co-doped polysilicon (poly-Si) in tunnel oxide passivation contact silicon solar cells has been investigated. We find that the introduction of N co-doping in P heavily doped poly-Si decreases its own work function; thus, the built-in potential of the poly-Si (n(+))/tunnel SiOx/c-Si (p) junction is notably enhanced. The electrical characteristics of interface states at tunnel SiOx/c-Si in the junction have been investigated by current/capacitance-voltage deconvolution. The measured results suggest that the interface state density is reduced, and the corresponding capture cross section ratio sigma(e)/sigma(h) is increased by three orders of magnitude in the junction with N co-doped poly-Si. The obtained results not only reveal the underlying mechanism of the enhanced contact passivation effect by introducing N co-doped poly-Si but also give an enlightening idea for the design of passivation contact structure in crystalline silicon solar cells.