Photo-Excited Switching and Enhancement of Dielectric Properties in Two-Dimensional Double Perovskite Phase Transition Thin Films

Optical controlling of solid-sate electric properties is emerging as a non-contact and nondestructive avenue to optimize the physical properties of electronic and optoelectronic devices. In term of strong light-material coupling, two-dimensional (2D) double perovskites hold great prospects to create photo-dielectric activities for high-performance device applications. Here, we have achieved the photo-excited switching and enhancement of dielectric properties in the orientational thin films of a 2D double perovskite, (C₄H₁₂N)₄AgBiI₈ (1, where C₄H₉NH₃⁺ is isobutylammonium). It undergoes a structural phase transition at 384 K (T_c), triggered by the dynamic ordering of organic cations and tilting motion of isometallic perovskite sheets. Most notably, the orientational thin films of 1 are extremely sensitive to light illumination, of which the dielectric constants can be facilely photo-switched between the low- and high-states. During this photo-switching process, the dielectric constants are enhanced with a magnitude up to ~350% under 405 nm, far beyond most of the inorganic phase transition counterparts. In addition, this photo-excited switching and enhancement of dielectric response exhibits an operational stability with superior anti-fatigue characteristics. Our work opens up a potential avenue for assembling high-performance optoelectronic devices with the controllable physical properties.