Ferroelectric-driven multifunctional heterojunction: Tunable phase transition, direct Z-scheme photocatalysis, and high-efficiency solar cells in SiI/ <b>α</b> -In2Se3

Ferroelectric two-dimensional materials provide a unique platform for designing multifunctional electronic and optoelectronic devices because of their switchable polarization and tunable electronic properties. In this paper, we design and study a multifunctional heterojunction of SiI/α-In2Se3. The calculated results indicate that when the polarization of α-In2Se3 switches from downward (P↓) to upward (P↑), a semiconductor-to-metal phase transition can be induced, which shows its inherent potential for reconfigurable photoelectric applications. In addition, the photocatalytic properties and solar cell performance of SiI/α-In2Se3↓ are systematically studied. It is found that SiI/α-In2Se3↓ presents a typical type-II band arrangement, enhanced light absorption across a wide spectral range, a moderate direct bandgap, and high charge carrier mobility. These characteristics enable it to be used as an efficient direct Z-scheme photocatalyst, achieving a remarkable solar-to-hydrogen efficiency of 34.62%. Besides, under 1% biaxial strain, its power conversion efficiency is as high as 21.56%, indicating strong application potential in high-efficiency solar cells. This work not only provides a deep understanding of the structure–property relationship in ferroelectric van der Waals heterostructures, but also highlights their important versatility and prospects in developing the next generation of tunable optoelectronics, advanced photocatalytic systems, and high-performance solar cells.