Characterization of Structure and Growth Evolution for nc-Si:H in the Tandem Photovoltaic Device Configuration

Spectroscopic ellipsometry (SE) is used to study the growth evolution of the bottom cell p-type doped and intrinsic hydrogenated silicon (Si:H) layers in p-i-n amorphous/nanocrystalline Si:H (a-Si:H/nc-Si:H) tandem photovoltaic (PV) devices. SE data collected in situ during the growth enables the identification of crystallite coalescence transitions in the surface roughness evolution, as well as the variations in optical response in the form of the complex dielectric function (ε = ε1 + iε₂). The latter indicates relative amounts of the a-Si:H and nc-Si:H components during mixed-phase Si:H 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 and can be understood on the basis of the growth evolution diagram.