Flexible Polycrystalline Ferroelectric Oxide Films With Ultrahigh Photovoltaic Current

Ferroelectric materials are promising for photovoltaics due to the bulk photovoltaic effect (BPVE), which offers advantages over conventional p‐n junction solar cells. However, the reliance on single‐crystalline, single‐domain films for high performance, which are challenging to synthesize, and their inherent brittleness hinder practical applications. This work presents a cost‐effective and scalable method for fabricating flexible PbTiO 3 (PTO) ferroelectric photodetectors using low‐temperature hydrothermal growth followed by room‐temperature corona poling. The poled polycrystalline PTO film exhibits a high short‐circuit photocurrent density of 2.3 mA cm −2 under 375 nm illumination, a performance comparable to that of single‐crystal PTO. This exceptional performance is attributed to two key factors: effective dipole and domain alignment induced by poling, and favorable electrical contact at the Ti electrode interface. The device also demonstrates excellent mechanical flexibility and operational stability, retaining 93.3% of its initial performance after 6000 switching cycles. Furthermore, leveraging the specific operating window of the PTO film, we demonstrate a proof‐of‐concept, secure optical communication system using a single‐wavelength, dual‐intensity encryption scheme to successfully transmit the letter “Z”. This work highlights the potential of these flexible PTO ferroelectric devices for wearable optoelectronics and secure data transmission.