Impact of phosphorus diffusion on n-type poly-Si based passivated contact silicon solar cells

Abstract

This paper describes the impact of phosphorus dopant concentrations in n-type passivated contact structures. Free carrier absorption (FCA) of the phosphorus doped poly-Si layers was studied by using different phosphorus dopant concentrations, with a range of from 9 × 1019 to 2.3 × 1020 cm−3, and different poly-Si layer thicknesses, with a range of from 30 to 200 nm. In the worst case, the effect of FCA reduce the short circuit current density by 0.89 mA/cm2. The impacts of tunnel SiO2 thicknesses, poly-Si thicknesses and diffusion temperatures on the performances of the poly-Si passivated contacts were studied. Phosphorus concentrations induced silicon surface field passivation play an important role in passivated contact structure. On the planar n-type mono crystalline-silicon substrates, excellent J0 value of 6.5 fA/cm2 was achieved by optimizing phosphorus doping in poly-Si films and silicon substrate. Different poly-Si thickness and diffusion temperature were studied simultaneously to optimize the phosphorous dopants in the poly-Si passivated contacts for the specified poly-Si thickness. N-type silicon solar cell have been fabricated by using the optimized poly-Si passivated contacts, as addressed above. Average efficiency of 22.52%, and best cell efficiency of 23.04% were demonstrated.