Tandem photovoltaic–photoelectrochemical GaAs/InGaAsP–WO₃/BiVO₄ device for solar hydrogen generation

We demonstrated highly efficient solar hydrogen generation via water splitting by photovoltaic–photoelectrochemical (PV–PEC) tandem device based on GaAs/InGaAsP (PV cell) and WO 3 /BiVO 4 core/shell nanorods (PEC cell). We utilized extremely thin absorber (ETA) concept to design the WO 3 /BiVO 4 core/shell heterojunction nanorods and obtained the highest efficiencies of generation, separation and transfer of the photo-induced charge carriers that are possible for the WO 3 /BiVO 4 material combination. The PV–PEC tandem shows stable water splitting photocurrent of 6.56 mA·cm −2 under standard AM1.5G solar light that corresponds to the record solar-to-hydrogen (STH) conversion efficiency of 8.1%.