Evaluation of vanadium substituted In2S3 as a material for intermediate band solar cells

The potential of vanadium substituted In2S3 as the active material in intermediate band solar cells (IBSCs) is investigated. The study is performed with a detailed balance model developed by Cuadra et al. that takes into account the shape and overlap of the absorption coefficients. Despite having values of the band gaps that could in principle lead to highly efficient IBSCs, it is found that cells with a practical thickness made of V2In14S24 have a lower efficiency limit than conventional single band gap solar cell materials. It has previously been explained why overlapping absorption coefficients requires the cell thickness to be optimized. In this work it is shown that the thickness dependency of the cell efficiency can have two peaks. In this particular case the two peaks occur at cell thicknesses around 1 μ m and 1 m. The reason for this double peaked dependency is processes where photons are emitted over one band gap and reabsorbed over another. Some of these processes can happen at very low rates and thus not give a significant contribution before a very thick cell is considered. For cells with a reasonable thickness, maximum efficiencies of 20.8% and 26.4% are found for light intensities corresponding to 1 and 1000 suns.