Effect of the valence band maximum control of Cu(In,Ga)Se₂ photoelectrode surface on water splitting

The effects of valence band maximum (VBM) position control on the Cu(In,Ga)Se2 (CIGS) photoelectrode surface during the photoelectrochemical (PEC) water splitting using CIGS thin films were studied. First, a hole-blocking layer was obtained by replacing Se with S atoms to achieve VBM position control. The corresponding increase in photocurrent density suppressed the recombination at the photoelectrode/electrolyte interface. Subsequently, the CdS layer with lower VBM position than the CIGS layer was deposited on the CIGS photoelectrode. The results showed that the onset potential and photocurrent density increased due to the VBM position of the CdS layer. This study shows that water splitting could be effectively improved by controlling the VBM position of the photoelectrode surface.