We report mechanically stacked InGaP (1.9 eV)/GaAs (1.42 eV)/InGaAsP (1.0 eV) triple junction solar cells fabricated with an advanced bonding technique using Pd nanoparticle arrays. High quality lnGaP/GaAs tandem top and InGaAsP bottom cells are grown on GaAs and MP substrates, respectively using solid-source molecular beam epitaxy (MBE). The lnGaAsP bottom cell has an open circuit voltage (V) of 0.49 V. which indicates that high performance lnGaAsP solar cells can be fabricated using solid-source MBE. A fabricated triple junction solar cell has a high efficiency of 25.6% with a high V of 2.66 V. (C) 2015 Elsevier B.V. All rights reserved.