One method that shows promise for producing hydrogen more easily and sustainably is photoelectrochemical (PEC) water splitting. PEC-based hydrogen generation solves the issue of solar persistency and offers a sustainable and environmentally friendly energy source. Despite significant attempts over the past few decades, no solar water splitting material has yet to meet the requirements of high efficiency, long-term stability, and affordability. The photoelectrode materials used in PEC must have band edge potentials at the surfaces, long-term stability against corrosion in the aqueous electrolyte, and enough voltage upon irradiation to split water. The oxygen and hydrogen evolution reaction are required for the charge transfer from the semiconductor's surface to the electrolyte. The most promising semiconductor materials are photocatalysts like TiO₂, WO₃, Fe₂O₃, Cu₂O, etc., because of their appropriate band gap and valance band structure. However, charge separation and conveyance are the main issues with PEC water splitting. The efficiency of the PEC process is increased by a number of techniques, including morphological control, defect introduction, heterojunction construction, and co-catalyst loading. The energy gap of n-type cuprous oxide (Cu₂O), which absorbs visible light up to a wavelength of 600 nm, makes it a suitable material for photocatalysis. Cu₂O's thickness is important as a photoelectrode since an incorrect thickness could deteriorate its photocatalytic qualities. By adjusting the Cu2O thickness, this work sought to improve the photocatalytic capabilities of Cu₂O electrodeposited on fluorine-doped tin oxide (FTO), or Cu₂O/FTO. Cu₂O/FTO electrochemical deposition allowed for the control of Cu₂O thickness by varying the deposition duration. Cu₂O's morphology altered from a leaf-like shape to an irregular facet shape with highly dense coverage when the deposition duration was varied from 8 to 40 minutes. The average thickness also rose from 450 to 1050 nm. Cu₂O/FTO achieved the highest photocurrent (150 and 158 µA under irradiation of 450 and 570 nm, respectively) at a thickness of 900 nm because of its extremely dense morphology and high absorption. Additionally, the charge diffusion was still good at a thickness of 900 nm. Further, the increase of Cu₂O film thickness higher than 900 nm caused low photocatalytic properties even though the morphology was highly dense, and the absorption was the highest. This state might result from Cu₂O's comparatively too high resistance, which led to inadequate charge dispersion.