Spectrally selective intermediate reflectors for tandem thin-film silicon solar cells

Thin-film silicon tandem solar cells consist of an amorphous silicon top cell and a microcrystalline silicon bottom cell stacked in series. In order to match the photocurrents of the top cell and the bottom cell, a proper photon management is essential. In this regard, we present the conceptual design and optical simulations of an intermediate reflector consisting of a stack of microcrystalline silicon oxide layers of different, alternating refractive indices. In contrast to 1-layer intermediate reflectors, the spectral and directional selectivity of these intermediate reflectors result in a gain for the top cell current while simultaneously increasing the charge carrier generation in the bottom cell.