X‐ray‐ultraviolet–visible‐near‐infrared photoresponses realized in a lead‐free hybrid perovskite ferroelectric through light‐induced ferro‐pyro‐phototronic effect

Abstract Due to the built‐in electric field induced by spontaneous polarization in hybrid perovskite (HP) ferroelectrics, the devices based on them exhibit excellent performance in self‐powered photodetection. However, most of the self‐powered photodetector are made of lead‐based HP ferroelectrics and have a relatively narrow photoresponse waveband. Although lead‐free HPs solve the problem of lead toxicity, their optoelectronic performance is inferior to that of lead‐based HPs and photoresponse waveband is limited by its optical band gap, which hinders their further application. To solve this problem, herein, a lead‐free HP ferroelectric (HDA)BiI₅ (HDA is hexane‐1,6‐diammonium) with large spontaneous polarization shows an enhanced photocurrent and achieves x‐ray‐ultraviolet–visible‐near‐infrared (x‐ray‐UV–Vis–NIR) photoresponse through the ferro‐pyro‐phototronic (FPP) effect. The ferroelectric, pyroelectric, and photovoltaic characteristics coupled together in a single‐phase (HDA)BiI₅ ferroelectric is an effective way to improve the performance of the devices. What is particularly attractive is that the FPP effect not only improves the optoelectronic performance of (HDA)BiI₅, but also achieves broadband photoresponses beyond its optical absorption range. Especially, the current boosting with an exceptional contrast of ~1100% and 2400% under 520 and 637 nm, respectively, which is associated with FPP effect. Meanwhile, single crystal self‐powered photodetector based on (HDA)BiI₅ also exhibit significant FPP effects even under high‐energy x‐ray, which owns an outstanding sensitivity of 170.7 μC Gy⁻¹ cm⁻² and a lower detection limit of 266 nGy s⁻¹ at 0 V bias. Therefore, it is of great significance to study the coupling of multiple physical effects and improve device performance based on lead‐free HP ferroelectrics. image