InP‐based multijunction tandem solar cells show great promise for high conversion efficiency and high radiation resistance. In this work, we present results on an InGaAs solar cell with a very high current density, 60 mA/cm2 (the highest ever reported), and an efficiency (η) of 10.2% under natural sunlight, and InP solar cell with η=18% under AM1 simulator, and InGaAs tunnel junctions with peak current densities exceeding 1000 A/cm2. Preliminary results on an InP/InGaAs tandem solar cell show the possibility of no interconnect voltage loss and that a patterned tunnel junction is necessary to allow current matching in the tandem by avoiding photons absorption in the InGaAs tunnel junction. Finally, our preliminary investigation on new multiquantum well InP cells indicates the strength of this alternative approach.