Modular perovskite-BiVO4 artificial leaves towards syngas synthesis on a m2 scale

Metal halide perovskite-based artificial leaves have emerged in recent years as a promising design towards direct solar fuel synthesis. However, the complexity of these layered devices and reliance on solution-based techniques hinders the scalability and performance of existing prototypes. Here, we utilise vacuum processing of the perovskite light absorbers, as an industrially compatible method to produce large-scale devices. Accordingly, we fabricate fully evaporated 10 cm2 PV devices sustaining a 1 V photovoltage, which allow perovskite-BiVO4 tandem photoelectrochemical devices with a selective Cu92In8 alloy catalyst to sustain unassisted water and CO2 splitting over 36 hours. To demonstrate the modularity of this design, we designed a 0.70.5 m2 “artificial tree” reactor containing a 1010 array of artificial leaves, which was benchmarked during the 3-days final outdoor demonstration of the EIC Horizon Prize “Fuel From the Sun”, at the Joint Research Center of the European Commission in Ispra, Italy. Such real-world tests reveal key insights into practical operation that are not encountered during standardised laboratory experiments, but are crucial for upscaling of emerging solar fuel technologies.