Characterization of structure and growth evolution for nc-Si:H in the tandem photovoltaic device configuration

Spectroscopic ellipsometry (SE) is used to study growth evolution of bottom cell p-type doped and intrinsic hydrogenated silicon (Si:H) layers in p-i-n amorphous/nanocrystalline (a-Si:H/nc-Si:H) tandem photovoltaic (PV) devices. From SE data collected in situ during Si:H growth, crystallite coalescence transitions are identified as well as variations in optical response, in the form of the complex dielectric function (ε = ε₁ + iε₂), also consistent with transitions from mixed (a+nc) to single phase nc-Si:H during growth. A growth evolution diagram for the i-layer in the tandem PV device configuration is constructed. Device properties are related to p- and i-layer structure.