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

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.