Under CopyrightGlunz, StefanAmbacher, OliverSchygulla, PatrickPatrickSchygulla2024-03-072024-03-072024978-3-8396-1986-5https://publica.fraunhofer.de/handle/publica/463869https://doi.org/10.24406/publica-276210.24406/publica-2762Tandem solar cells are required for higher photovoltaic module efficiencies and thus reduced costs and land demand. This thesis was concerned with the development of a two-terminal III-V//Si triple-junction solar cell. Two compound semiconductors, AlGaAs and GaInAsP, were investigated. The samples were grown lattice matched on GaAs substrates using metalorganic vapor phase epitaxy. GaInAsP exhibited a high performance with a minimum loss to the radiative limit of 18 mV in a rear-heterojunction solar cell. An optical parameter morphing method was optimised to generate continuous refractiv index data for arbitrary absorber compositions. The robustness of the method was experimentally confirmed by a comparison to literature values as well as spectral ellipsometry, external quantum efficiency, and reflection measurements. With the complex refractive index data the target absorber thicknesses in multi-junction solar cells were adjusted by transfer matrix modelling to achieve current match between the subcells. The triple-junction solar cell achieved a power conversion efficiency of 35.9 % under the AM1.5g solar spectrum, the highest efficiency for monolithic silicon based cells to date.enAlternative EnergiequellenErneuerbare EnergienFestkörperphysikNachhaltigkeitEnergieeffizienzMaterialwissenschaftDDC::600 Technik, Medizin, angewandte Wissenschaften::620 Ingenieurwissenschaften::621 Angewandte Physikdoctoral thesis