Harnessing sunlight for hydrogen production through photoelectrochemical (PEC) water splitting is a promising approach in clean energy. Despite challenges in materials science, copper oxide semiconductors like cuprous oxide (Cu2O) offer scalability and abundance. Efforts to enhance solar energy utilization involve improving light absorption, particularly focusing on harnessing infrared (IR) light through upconversion materials like triplet-triplet annihilation-based upconversion (TTA-UC). By combining a Cu2O photocatalyst with an upconverter, a novel device has been developed to improve light-harnessing properties. The study also explores the use of thin Au layers to enhance the electronic junction and film quality of Cu2O on substrates, leading to improved photoelectrochemical and optical properties for solar-assisted water splitting.