We study silicon based thin films (silicon sub-stoichiometric oxides and oxi-nitrides, amorphous and nanocrystalline) which find important applications as passivating layers in high efficiency Si based heterojunction solar cells. Good conductivity and low parasitic absorption are mandatory in order to improve solar cell efficiency. We study transport properties at the nano scale to understand the link between structural properties and conductivity, macroscopical transport and optical properties in order to clarify the physics of the passivation mechanisms. We study, in addition, innovative photovoltaic materials like perovskite nanocrystals which show very promising stability and high solar conversion efficiency.
The present study reports on the investigation of electrical transport properties of nanocrystalline (nc-) SiOxNy. Non-stoichiometric nc-SiOxNy films deposited by Plasma Enhanced Chemical Vapor Deposition have been studied by conductive Atomic Force Microscopy (AFM). The analyses of samples subjected to different thermal treatments and the comparison with nc-Si:H films have allowed us to clarify the role of crystallization and O content on the local conductivity of the layers. We show that the annealing treatment promotes an enhancement of conductance, a redistribution of the conductive grains in the layers and the activation of B doping. Current-voltage characteristics locally performed using the conductive AFM-tip as a nanoprobe have been modelled with thermionic emission transport mechanism.
The study has been published on:
Journal of Alloys and Compounds 725, 163, 2017
Maria Antonietta Fazio, Martina Perani, Nils Brinkmann, Barbara Terheiden, Daniela Cavalcoli https://doi.org/10.1016/j.jallcom.2017.07.151