Ultrasensitive polarized-light photodetectors based on 2D hybrid perovskite ferroelectric crystals with a low detection limit

Polarized-light photodetectors are the indispensable elements for practical optical and optoelectronic device applications. Two-dimensional (2D) hybrid perovskite ferroelectrics, in which the coupling of spontaneous polarization (Ps) and light favors the dissociation of photo-induced carriers, have taken a booming position within this portfolio. However, polarized-light photodetectors with a low detection-limit remain unexplored in this 2D ferroelectric family. In this work, the high-quality individual crystals of a 2D perovskite ferroelectric, BA2CsPb2Br7 (1, where BA+ is n-butylammonium), were used to fabricate ultrasensitive polarized-light detectors. Its unique bilayered structural motif results in quite strong electric and optical anisotropy with a large absorption ratio of αc/αa ≈ 3.2 (λ = 405 nm). Besides, the presence of ferroelectric Ps also endows high built-in electric field along the polar c-axis that favors photoelectric activities. Under an extremely low detectable limit of 40 nW/cm2, the detector of 1 exhibits a notable dichroism ratio (Iphc/Ipha ≈ 1.5), a large responsivity of ~39.5 mA/W and a specific detectivity of ~1.2 × 1012 Jones. Moreover, crystal-based devices of 1 also exhibit a fast response speed (~300 μs) and excellent anti-fatigue merits. This work highlights great potentials of hybrid perovskite ferroelectrics toward polarized-light photodetection.