Four terminal cell analysis of amorphous/microcrystalline Si tandem cell

For the optimum design of hydrogenated amorphous/microcrystalline silicon (a-Si:H//spl mu/c-Si:H) tandem solar cells, we have developed an analysis method using a four terminal structure with the TCO (ZnO:Ga) layer as an intermediate electrode. The top and bottom cell characteristics (IV-curve and spectral response) can be measured individually. The interlayer thickness dependence of the cell performance indicates the optical interference at the interlayer affects not only the short circuit current but also the open circuit voltage particularly in the bottom cell. It was also found that the shallower texture of 6% haze Asahi-U and lower carrier density of the interlayer are beneficial for the tandem cell. The lower carrier density results in the open circuit voltage of 0.58 V for the bottom cell. The optical, electrical and structural roles of the interlayer are discussed.