N-type thin-film polycrystalline-silicon solar cells using a seed layer approach

N-type thin-film polycrystalline-silicon solar cells were fabricated on alumina substrates. The polycrystalline silicon material was made by overdoping of AIC seed layers with phosphorus atoms followed by epitaxial thickening with low-pressure chemical vapor deposition (LPCVD) at 1000°C. The cells have i/p+ amorphous Si heterojunction emitters and show an average V_OC of 455 mV, an average J_SC of 16.5 mA cm^-2 and a record efficiency of 5.0%. The excess out-diffusion of phosphorus from the seed layers during the epitaxial growth resulted in a non-ideal doping profile, which is believed to be the main limitation of the current density besides the material quality. In addition, the non-optimized heterojunction emitter deposition for n-type polycrystalline silicon and the lack of superior light trapping also limited the present cell performance.