Under CopyrightFeifel, MarkusMarkusFeifelLackner, DavidDavidLacknerOhlmann, JensJensOhlmannVolz, KerstinKerstinVolzHannappel, ThomasThomasHannappelHermle, MartinMartinHermleBenick, JanJanBenickDimroth, FrankFrankDimroth2022-03-1426.2.202127.2.20212020https://publica.fraunhofer.de/handle/publica/41015610.24406/publica-r-41015610.1109/PVSC45281.2020.9300594Epitaxial III-V on silicon multi-junction solar cells allow to increase the conversion efficiency of single-junction silicon devices. We report progress on the development of high-efficiency GaInP/GaAs/Si triple-junction devices over the last two years. The AM1.5g conversion efficiency has been increased from 19.7% to 22.3%, 24.3%, and finally a value of 25.9% could be achieved. The improvement was enabled by a reduction of nucleation-related crystal defects in the silicon to gallium phosphide transition and a reduction of parasitic absorption within the metamorphic GaAsP buffer structure which was limiting the current in the silicon subcell. By increasing the bandgaps in the graded buffer structure, a ∼2x reduction of the threading dislocation density was observed and the short-circuit current density increased by 22% relative. A majority barrier was identified and could be suppressed to obtain a new record conversion efficiency of 25.9% with an open-circuit voltage of 2.647 V, a short-circuit current density of 12.2 mA/cm 2 and a fill factor of 80.2%.enPhotovoltaikSilicium-PhotovoltaikIII-V- und Konzentrator-PhotovoltaikDotierung und DiffusionIII-V Epitaxie und Solarzellen621697conference paper