Large-Scale Stable Hybrid Perovskite-Based Photoelectrochemical Water Splitting Devices

Photoelectrochemical (PEC) water splitting is a promising technology for directly converting solar energy into easily storable green hydrogen (H₂). Yet, the use of PEC devices is not widespread because of their low performance, poor stability, and the absence of large-scale deployment. Recently, the lead halide perovskite (LHP)-based integrated photoelectrodes has helped overcome these drawbacks and facilitated unbiased PEC water splitting systems, achieving high solar-to-hydrogen (STH) efficiency exceeding 13%. However, despite the significant role of large-scale deployment and stable long-term operation for practical commercialization, research in the field of LHP-based photoelectrodes has been limited to STH improvements. Herein, we present novel strategy involving the bathing of LHP film in an antisolvent containing cyclohexylammonium iodide (CHAI) for the fabrication of high-quality large-size LHP films for use in practical unbiased PEC water splitting. The effects of CHAI-antisolvent bathing and its impact on the performance of large-area LHP film-based coplanar devices are demonstrated. Consequently, parallelly illuminated coplanar LHP-based photoelectrodes with dimension of 8 cm × 8 cm could be stably operated without any applied bias, exhibiting a record-high STH efficiency of 9.89% and T₈₀ (the time at which the photocurrent density drops to 80% of its initial value) of 24 h with a considerable hydrogen production rate. Furthermore, degradation mechanism of LHPs during PEC operations will be briefly presented. Through operando electrochemical impedance spectroscopy analysis and in-situ photoluminescence analysis, we found that charge accumulation at the interface of PEC device/electrolyte promotes ion migration in the perovskite layer. Moreover, the highly increased capacitance and trap density at hole transport layer measured from drive-level capacitance profiling elucidated not only the location of the accumulated charge but also the mechanism of accelerated ion migration. Our findings provide a pathway for LHP-based PEC water splitting devices to achieve mass production of solar hydrogen and high operational stability.