In situ-grown organo-lead bromide perovskite-induced electroactive γ-phase in aerogel PVDF films: an efficient photoactive material for piezoelectric energy harvesting and photodetector applications.

The unique combination of piezoelectric energy harvesters and light detectors progressively strengthens their application in the development of modern electronics. Here, for the first time, we fabricated a polyvinylidene fluoride (PVDF) and formamidinium lead bromide nanoparticle (FAPbBr3 NP)-based composite aerogel film (FAPbBr3/PVDF) for harvesting electrical energy and photodetector applications. The uniform distribution of FAPbBr3 NPs in FAPbBr3/PVDF was achieved via the in situ synthesis of FAPbBr3 NPs in the PVDF matrix, which led to the stabilization of the γ-phase. The freeze-drying process induced an interconnected porous architecture in the composite film, making it more sensitive to small mechanical stimuli. Owing to this unique fabrication technique, the constructed aerogel film-based nanogenerator (FPNG) exhibited an output voltage and current of ∼26.2 V and ∼2.1 µA, respectively, which were 5-fold higher than that of the nanogenerator with the pure PVDF film. Also, the sensitivity of FPNG upon the irradiation of light was demonstrated by the output voltage reduction of ∼38%, indicating its capability as a light sensing device. Furthermore, the prepared FAPbBr3/PVDF composite was found to be an efficient candidate for light detection applications. A simple planar photodetector was fabricated with the 8.0 wt% FAPbBr3 NP-loaded PVDF composite, which displayed very high responsivity (8 A/W) and response speed of 2.6 s. Thus, this exclusive combination of synthesis and fabrication for the preparation of electro-active films opens a new horizon in the piezoelectric community for effective energy harvesting and light detector applications.

Morphological interference of two different cobalt oxides derived from a hydrothermal protocol and a single two-dimensional metal organic framework precursor to stabilize the ß-phase of PVDF for flexible piezoelectric nanogenerators.

Here, we have fabricated a piezoelectric nanogenerator (PENG) composed of a Co-oxide (Co3O4) doped electro active PVDF based nanocomposite for efficient piezoelectric energy harvesting application where the Co3O4 inclusion favours nucleation and polar ß-phase stabilization in the nanocomposite. The morphological effect on the nucleation and ß-phase stabilisation of PVDF has been explored experimentally. The flake-like morphology of Co3O4 nanoparticles, synthesized by using a MOF, has a more effective surface area to nucleate and stabilise the ß-phase of PVDF than that of rod-like (hydrothermal) and spherical (commercial) nanoparticles. The PENG with PVDF and the 1.5 wt% MOF based Co3O4 (MPNG) shows an excellent open circuit voltage (∼37 V) and short circuit current (∼0.711 µA) upon human finger tapping. The maximum power density generated from the MPNG is ∼8.55 µW cm-2, which is well sufficient for the driving of portable electronic devices like LEDs, calculator wrist watches, humidity sensors etc. Also, from various easily accessible mechanical and biomechanical energy sources like heel pressing, walking, and machine vibration, the MPNG is capable of harvesting energy.