Enhanced electro-active phase in a luminescent P(VDF–HFP)/Zn2+ flexible composite film for piezoelectric based energy harvesting applications and self-powered UV light detection

We have prepared a flexible polymer composite film containing poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF–HFP)) and Zn2+ for the fabrication of a multifunctional piezoelectric based nanogenerator (MFNG), where a traditional electrical poling treatment was avoided. The desirable amount of Zn2+ yields more than 99% of electro-active phases in the P(VDF–HFP) matrix that co-operates to enhance the dielectric properties of the composite film via hydrogen bonding interactions. In situ thermal Fourier transform infrared (FT-IR) spectroscopy affirms the improved thermal stability of the electro-active β-phase and the β → γ phase transition temperature in the Zn2+ doped composite film. It also shows UV absorption and intense blue light emission confirmed by a CIE 1931 chart that gives it applicability as a flexible optical sensor. The MFNG behaves as an efficient mechanical energy harvester that delivers an open-circuit voltage ∼6 V and an output power of 2.4 μW and successfully enables the charging of a capacitor by simple repetitive finger touch and release motions (a pressure amplitude of ∼14 kPa). The UV light sensing ability of the MFNG is confirmed under the continuous application and removal of applied stress, which is very promising for designing versatile self-powered optoelectronic smart sensors. Our approach is very simple and cost effective for the construction of a new class of flexible multifunctional energy harvesters that have wonderful applications in the areas of piezo-photonics, wireless detection and flexible self-powered opto-electronics.