Ferroelectric Photodetector with High Current on–off Ratio (∼1 × 10⁴%) in Self-Assembled Topological Nanoislands

Ferroelectric photodetectors have attracted intensive interest because of the polarization-dependent photoresponse and efficient carrier separation and transport. However, the photoresponsivity and photo-to-dark current (on–off) ratio are limited by the large bandgap. Here, an enhanced current on–off ratio (1.15 × 104%) was discovered at cross-shaped charged domain walls topologically confined in self-assembled BiFeO3 nanoisland arrays. Different from the conventional nonconductive ferroelectric domains, the center-type topological quad-domains also exhibit tunable conductance by external electric field, which stimulates the distinct current on–off ratio of 1.12 × 104% at center-convergent and 1.65 × 103% at center-divergent quad-domains, respectively. Furthermore, the prototype devices based on these ferroelectric nanoislands exhibit a high photoresponsivity (1.8 × 103A/W) and broadband spectrum response (from visible to infrared), demonstrating the outstanding photoelectric performance in the low-dimensional ferroelectric topological textures.