Light-regulated pyro-phototronic effects in a perovskite Cs2SnI6-reinforced ferroelectric polymer hybrid nanostructure.

Abstract

The 'pyro-phototronic effect' plays a nontrivial role in advancing ferroelectric (FE) devices of light detectors, light-emitting diodes, and other smart technologies. In this work, a premier FE copolymer, poly(vinylidene fluoride-co-trifluoro ethylene) (P(VDF-TrFE)), is reinforced with a lead-free double perovskite, Cs₂SnI₆, to render profound properties in a hybrid nanostructure. It presents a unique example of the coupling of ferro-, pyro- and piezo-electrics to the 'photoexcitation' of exotic charges that actively empower the synergetic features. Cs₂SnI₆ embodied in small crystallites therein is distorted in a non-centrosymmetric class of a rhomboid crystal structure (a new phase) rather than a well-known centrosymmetric face-centred cubic (fcc) phase. It boosts the emerging phototronic properties. A systematic study of the bulk heterojunction reveals the four-stage pyro-phototronic response of transient photocurrent under visible light illumination of a solar simulator (intensity ∼100 mW cm^-2). Illumination at a frequency of 0.025 Hz induces a temporal temperature change, ΔT → 3.1 K, in the system, leading to induced pyroelectricity in an integrated circuit. The rise time and response time for the heterojunction are observed as ∼326 ms and ∼225 ms, respectively. The output pyro-phototronic current increases as ΔT increases in an on-off cycle. As a result, the integrated pyro-phototronic effect can be utilized to empower optoelectronic devices and harvest stray 'thermal energy' for running small energy devices.