Measuring the Electronic Properties of Poly-Si Thin Film Solar Cells Deposited on Textured Substrate

Electrical properties of PECVD produced poly-Si photovoltaic layers on the various textured substrates showing the light trapping effect have been investigated using an AC-conductivity technique. From temperature dependence of electron (hole) conductivities using n-i-n (p-i-p) structures, the Fermi level of the poly-Si layer on the slightly textured substrates is found to locate at the center of the band gap and this material is 'truly' intrinsic. As RMS roughness of the textured substrate, sigma increases, the Fermi level becomes close to conduction band edge, and finally, the poly-Si layer on the highly textured substrate exhibits n-type character even though any deposition conditions for the poly-Si layers are not changed at all. Changes in electrical conductivities of the poly-Si thin films in conjunction with the results on photovoltaic performances and microstructure are also discussed