Spectral Characteristics of Thin-Film Stacked-Tandem Solar Modules

Abstract

The device current–voltage (I–V) parameters of thin-film silicon stacked-tandem solar modules consisting of amorphous and microcrystalline silicon have been investigated under various spectral irradiance distributions. Spectrometric characterization method by the current mismatch perturbation has been developed using a large-area multisource solar simulator consisting of Xe lamps and halogen lamps with adequate optical filters. This method enables us to reveal the current-limited component cell and to specify the most suitable spectral distribution for tandem modules to obtain the best performance. Practical procedures for determining the irradiance level for a given single-source solar simulator have been demonstrated in order to carry out I–V measurement for tandem cells under nearly standard test conditions (STC). We have determined the differential of I–V parameters at various spectral distributions and found that the procedure using a reference tandem cell and its efficiency at STC could minimize variation from the true value even if the spectral distribution deviates from the reference.