Ferroelectric perovskite detects left- or right-handed circularly polarized light and can switch preference electrically

# What researchers built A team led by LUO Junhua and LI Lina at the Fujian Institute of Research on the Structure of Matter created an optically active hybrid perovskite, written as BnA2MA2Pb3Br10. The crystal structure and composition combine ordered organic cations with a distorted inorganic lead–bromide framework to break inversion symmetry and produce a spontaneous ferroelectric polarization along the crystal c axis.

# How the detector works The material is both ferroelectric and exhibits a bulk photovoltaic effect. Under 405 nm illumination the crystal generates a photovoltaic response without external bias. Because the material is optically active, its response depends on the handedness of circularly polarized light (CPL). The ferroelectric polarization can be switched electrically (poling), and switching reverses both the direction of the photovoltaic signals and which CPL handedness produces the stronger photocurrent.

# Measured device performance The reported device parameters under the conditions described are:

• Open-circuit voltage (VOC): approximately 0.25 V under 405 nm illumination.
• Responsivity: 18.3 mA W^-1.
• Specific detectivity: 3.2 × 10^11 Jones at an incident intensity of 2.2 μW cm^-2.

These figures apply to the presented photoresponse and illustrate that the device operates without an external power source while providing measurable sensitivity to CPL.

# Circular polarization sensitivity and switching At zero applied bias the photocurrent shows a clear difference between left- and right-handed CPL, with an anisotropy factor (a quantitative measure of selectivity) reaching up to 0.62. After poling the ferroelectric in opposite directions (positive vs negative), the relative photocurrent responses to left- and right-handed CPL swap. In other words, electrical polarization reversal flips the device's CPL preference.

# Why this matters CPL detection is relevant to technologies such as quantum communication, chiral sensing, and high-density optical information storage. Conventional CPL detectors often need bulky optical elements or fixed chiral semiconductors. This material demonstrates two features that can simplify or add functionality to future systems:

• Self-powered operation thanks to the bulk photovoltaic effect.
• Electrically reconfigurable CPL selectivity via ferroelectric switching, enabling dynamic encoding or multiplexing of polarization-based signals.

# Practical takeaways and next questions The study provides a materials-level route to detectors that combine intrinsic chirality with ferroelectric switchability. The reported device performance metrics show measurable sensitivity and reasonable detectivity under low light. Future practical work would need to address device integration, stability, scalability, wavelength range, speed, and how the material performs in realistic operating environments.