Organometal Halide Perovskite‐Based Photoelectrochemical Module Systems for Scalable Unassisted Solar Water Splitting

Despite achievements in the remarkable photoelectrochemical (PEC) performance of photoelectrodes based on organometal halide perovskites (OHPs), the scaling up of small‐scale OHP‐based PEC systems to large‐scale systems remains a great challenge for their practical application in solar water splitting. Significant resistive losses and intrinsic defects are major obstacles to the scaling up of OHP‐based PEC systems, leading to the PEC performance degradation of large‐scale OHP photoelectrodes. Herein, a scalable design of the OHP‐based PEC systems by modularization of the optimized OHP photoelectrodes exhibiting a high solar‐to‐hydrogen conversion efficiency of 10.4% is suggested. As a proof‐of‐concept, the OHP‐based PEC module achieves an optimal PEC performance by avoiding major obstacles in the scaling up of the OHP photoelectrodes. The constructed OHP module is composed of a total of 16 OHP photoelectrodes, and a photocurrent of 11.52 mA is achieved under natural sunlight without external bias. The successful operation of unassisted solar water splitting using the OHP module without external bias can provide insights into the design of scalable OHP‐based PEC systems for future practical application and commercialization.