Tailoring of a visible-light-absorbing biaxial ferroelectric towards broadband self-driven photodetection

In terms of strong light-polarization coupling, ferroelectric materials with bulk photovoltaic effects afford a promising avenue for optoelectronic devices. However, due to severe polarization deterioration caused by leakage current of photoexcited carriers, most of ferroelectrics are merely capable of absorbing 8–20% of visible-light spectra. Ferroelectrics with the narrow bandgap (<2.0 eV) are still scarce, hindering their practical applications. Here, we present a lead-iodide hybrid biaxial ferroelectric, (isopentylammonium) 2 (ethylammonium) 2 Pb 3 I 10 , which shows large spontaneous polarization (~5.2 μC/cm 2 ) and a narrow direct bandgap (~1.80 eV). Particularly, the symmetry breaking of 4/ mmm F mm 2 species results in its biaxial attributes, which has four equivalent polar directions. Accordingly, exceptional in-plane photovoltaic effects are exploited along the crystallographic [001] and [010] axes directions inside the crystallographic bc -plane. The coupling between ferroelectricity and photovoltaic effects endows great possibility toward self-driven photodetection. This study sheds light on future optoelectronic device applications.