High-photovoltage GaAs vertical epitaxial monolithic heterostructures with 20 thin p/n junctions and a conversion efficiency of 60%

Photovoltaic power converting III–V semiconductor devices based on the Vertical Epitaxial HeteroStructure Architecture (VEHSA) design have been achieved with up to 20 thin p/n junctions (PT20). Open circuit photovoltages in excess of 23 V are measured for a continuous wave monochromatic optical input power of ∼1 W tuned in the 750 nm–875 nm wavelength range. Conversion efficiencies greater than 60% are demonstrated when the PT20 devices are measured near the peak of their spectral response. Noticeably, the PT20 structure is implemented with its narrowest ultrathin base having a thickness of only 24 nm. In the present study, the spectral response of the PT20 peaks at external quantum efficiency (EQE) of 89%/20 for an input wavelength of 841 nm. We also performed a detailed analysis of the EQE dependence with temperature and for VEHSA structures realised with a varied number of p/n junctions. The systematic study reveals the correlations between the measured conversion efficiencies, the EQE behavior, and th...