Above Room-Temperature Phase Transition in Helicoidal 2D Halide Perovskite Enables Pyro-Phototronic Control

Abstract

Bridging pyro-phototronic and ferroelectric properties in a single material not only gives rise to exotic physical phenomena but also provides strategy to build-up next-generation multi-functional energy harvesting devices. The layered halide perovskites are emerging class of synergetic 2D-materials of exceptional light-induced functionalities. Here, we report synthesis of a lead-free perovskite (3-fluorobenzylamine)2CuCl4 of partially fluorinated aromatic rings. Molecular chains are chiral in helicoids so to render flexibility, energy-transfer, and freedom to tailor tunable pyro-phototronics on light illumination. The fluorinated framework promotes ferroelectric-to-paraelectric transition point (TC), as high as \textasciitilde 412 K of wide range of workably. A giant pyro-photronic response is distinctly evident even upon UV-visible light-illuminations. A significantly high pyro-photronic current of 60 nA was achieved under an illumination of λex\textasciitilde 365 nm (27 mW) in a self-powered configuration. Consequently, an intricate coupling of the spontaneous polarization to the optical properties is visualized from the piezo response force microscopy (PFM) responses. In particular, the polar domains get diminished reversibly in on-off steps of the light irradiations. It indicates, the light provides another degree of the freedom to control the features for the applications of optoelectronic devices, optical memories, photo/thermo-chromic systems, and energy-harvesters.