Enhanced domain wall conductivity in photosensitive ferroelectrics Sn₂P₂S₆ with full-visible-spectrum absorption

Recent optical stimulation suggests a vital non-contact pathway to manipulate both macroscopic and microscopic ferroelectric properties and paves the foundation for optoelectronics devices. However, up to date, most optical-related manipulation of ferroelectric properties is restricted due to their intrinsic bandgap and limited visible light spectrum absorption. Here, we reveal non-oxide Sn₂P₂S₆ single crystal possesses full-visible-spectrum absorption (from 300 to 800 nm) with a unique disproportionation mechanism of photoexcited Sn ions and Urbach tail, which is not contradicting to the intrinsic band gap. Interestingly, we observed the existence of conductive domain walls (c-DW) and the light illumination induced significant enhancement of the domain wall conductivity caused by such disproportionation reaction. In addition, the domains separated by c-DW also exhibited noticeable electrical conductivity difference in the presence of optical illumination owing to the interfacial polarization charge with opposite signs. The result provides a novel opportunity for understanding the electrical conductivity behavior of the domains and domain walls in ferroelectrics with full-visible-spectrum absorption and achieving greatly enhanced performances for optoelectronics.