The scalability of our system was demonstrated by the 25 cm 2 SVG-PC sheet (Fig. ). The weight (19.8±0.1 mg cm -2 ) and device density (0.44±0.02 g cm -3 ) were further reduced in large-scale samples compared to the 1 cm 2 counterparts. In artificial seawater, the H2 evolution rate and STH efficiency of the large sheet were 9.87 mmol m -2 h -1 and 0.063%, respectively. The drop in the performance could be attributed to a decrease in incident light due to water condensation and the use of plexiglass as the reactor window, as well as gas leakage that might be present in the scaled-up reactor. Stoichiometric overall water splitting (H 2 :O 2 ratio of 2.4) was also achieved (Fig. , Supplementary Fig. ). Thus, the potential scalability of the hybrid device was successfully demonstrated.