Optical to electrical power converting devices are achieved with breakthrough performance using a Vertical Epitaxial HeteroStructure Architecture (VEHSA design). The III-V semiconductor devices allow achieving a near-optimum responsivity, an improved photovoltage output compared to p/n junctions with standard thicknesses. The ultrahigh conversion efficiencies were obtained by monolithically integrating several thin GaAs photovoltaic junctions tailored with submicron absorption thicknesses and grown in a single crystal by epitaxy. Experimental evidence of the significant impact of photon recycling in these photovoltaic devices has been observed. The devices exhibited a near optimum responsivity of up to 0.645A/W, corresponding to an external quantum efficiency of ~94%. Recent progresses include: -The highest optical to electrical efficiency ever achieved; -The highest output powers ever reported for a high-efficiency monolithic PV cell with 5.87W of converted output from a CW laser; -The highest efficiencies ever reported for any types of optical to electrical power conversion devices simultaneously combining high photovoltage and output powers (> 5W at > 7V with > 60% efficiency and > 3W at > 14V with > 60% efficiency); -The highest photovoltage ever reported for monolithic photovoltaic semiconductor heterostructures with measured Voc > 23V; -the thinnest p/n junctions ever implemented successfully with high-performance, with GaAs bases as small as 24nm.