High-efficiency integrated multijunction photovoltaic/electrolysis systems for hydrogen production

In this study, two integrated PV/electrolysis systems were studied. An integrated PV/electrolysis device is a device where the PV system and the electrolyser are combined into a single system. In the case studied here, the areas of the PV device and the electrolyzer are identical. Multijunction photovoltaic (PV)/electrolysis configurations were investigated, and a high solar-to-hydrogen conversion efficiency cell demonstrated. The energy diagram of the configuration has been evaluated and exemplified with n/p, n/p-GaInP/GaAs(Pt)/KOH electrolyte and triple-junction p–i–n a-Si(Pt)/KOH electrolyte photovoltaic/electrolysis cells. The efficiency of the cells was determined based on the short-circuit photocurrent. Measurements were obtained both indoors under 100-mW/cm2 insolation, and outdoors. For the a-Si system, a 7.8% solar-to-hydrogen conversion efficiency was demonstrated. For the GaAs/GaInP2 system, the solar-to-hydrogen conversion efficiency was over 16%.