Makita, K.K.MakitaMizuno, H.H.MizunoTayagaki, T.T.TayagakiAihara, T.T.AiharaOshima, R.R.OshimaShoji, Y.Y.ShojiSai, H.H.SaiTakato, H.H.TakatoMüller, RalphRalphMüllerBeutel, PaulPaulBeutelLackner, DavidDavidLacknerBenick, JanJanBenickHermle, MartinMartinHermleDimroth, FrankFrankDimrothSugaya, T.T.Sugaya2022-03-062022-03-062020https://publica.fraunhofer.de/handle/publica/26128010.1002/pip.3200Multijunction (MJ) solar cells achieve very high efficiencies by effectively utilizing the entire solar spectrum. Previously, we constructed a III‐V//Si MJ solar cell using the smart stack technology, a unique mechanical stacking technology with Pd nanoparticle array. In this study, we fabricated an InGaP/AlGaAs//Si three‐junction solar cell with an efficiency of 30.8% under AM 1.5G solar spectrum illumination. This efficiency is considerably higher than our previous result (25.1%). The superior performance was achieved by optimizing the structure of the upper GaAs‐based cell and employing a tunnel oxide passivated contact Si cell. Furthermore, we examined the low solar concentration performance of the device and obtained a maximum efficiency of 32.6% at 5.5 suns. This performance is sufficient for realistic low concentration photovoltaic applications (below 10 suns). In addition, we characterize the reliability of the InGaP/AlGaAs//Si three‐junction solar cell with a damp heat test (85 °C and 85% humidity for 1000 h). It was confirmed that our solar cells have high long‐term stability under severe conditions. The results demonstrate the potential of GaAs//Si MJ solar cells as next‐generation photovoltaic cells and the effectiveness of smart stack technology in fabricating multijunction cells.enPhotovoltaikIII-V und Konzentrator-PhotovoltaikIII-V Epitaxie und Solarzellensolar cellsstackconcentrator621697journal article