Doped silicon oxide layers for tandem silicon solar cells

Improved light trapping and the reduction of parasitic absorption losses in doped silicon layers of thin film silicon based multijunctions can be accomplished by the replacement of the doped layers by doped silicon oxide. In this contribution we will focus on both p-type and n-type silicon oxide. We report on the optimization of p-doped silicon oxide which is a compromise between optical (low refractive index) and electrical (high conductivity) properties for use as the p-layer in thin film silicon cells. Because of its bigger bandgap, smaller parasitic absorption loss, a greater response in the blue part of the spectrum has been achieved compared to the standard player. When the n-type silicon oxide is used as a reflecting layer, it improves the current in the a-Si:H cell. In addition, the material properties of the heterogeneous n-doped silicon oxide have been studied by FTIR and XPS. FTIR measurements reveal the dominant Si-O bonding configurations and the contributions of oxygen related modes show correlations to relative oxygen percentages obtained using XPS data.