Flexible Hybrid Eu 31 Doped P(VDF-HFP) Nanocomposite Film Possess Hypersensitive Electronic Transitions and Piezoelectric Throughput Prakriti Adhikary, 1 Samiran Garain, 1 Shanker Ram, 2 Dipankar Mandal 1 1 Organic Nano-Piezoelectric Device Laboratory (ONPDL), Department of Physics, Jadavpur University, Kolkata, West Bengal 700032, India 2 Materials Science Centre, Indian Institute of Technology, Kharagpur, West Bengal 721302, India Correspondence to: D. Mandal (E-mail: dipankar@phys.jdvu.ac.in) Received 24 March 2016; accepted 20 July 2016; published online 00 Month 2016 DOI: 10.1002/polb.24144 ABSTRACT: A novel red light-emitter made of Eu 31 doped self- poled electroactive poly(vinylidene fluoride–hexafluoropropy- lene) [P(VDF-HFP)] hybrid nanocomposite film possesses piezo- electric throughput that is suitable for flexible piezoelectric nanogenerator (PNG) fabrication. We observed that PNG is enabled to generate an open-circuit voltage of 5 V and 0.35 lA of short-circuit current under an applied pressure amplitude of 10.4 kPa. By simple mechanical energy scavenging, PNG demonstrates an ability to light more than ten blue commercial light emitting diodes instantly, without using an energy- storage device. Additionally, it successfully charges up capaci- tors by simple repeating finger touch motion, which indicates its potency as an efficient energy harvesting power source. The high performance of PNG is due to well-coated Eu 31 with P(VDF-HFP) in a hybrid nanocomposite so it displays improved dielectric permittivity and energy storage capacity. This flexible composite film also possesses a hypersensitive electronic tran- sition as it responds by an intense red light-emission con- firmed by the CIE 1931 chart. This enables applications in piezo-photonics as a high-performance, energy-saving, flexible solid-state red light emitter. V C 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 00, 000–000 KEYWORDS: electroactive phase; high performance polymer; composites; fluorescence; self-poled piezoelectric nanogenerator INTRODUCTION Dispersion of rare-earth ions in a dielectric insulator at atomic scales creates an important family of light-emitters, useful for versatile applications, lighting, dis- play, optical communication, laser and biological imaging. 1–9 Among them, Eu 31 ions exhibit a wide spectrum (6000– 200 cm 21 ) of 7 Fj (J 5 0 ! 6) levels of a ground state multi- plet. This is of both fundamental and technological impor- tance due to their characteristic light emission properties in the ultraviolet, visible, and near infrared regimes consisting of extremely sharp bands with long lifetimes and internal quantum efficiency. 6,8 However, uniform Eu 31 dispersibility in a pertinent host with good thermal stability and mechani- cal strength is a challenge in device fabrication, particularly for a wide range of applications. Thus, one acceptable solu- tion is to disperse Eu 31 into an organic, inorganic, or an organic-inorganic hybrid in a desirable device shape. 10,11 A suitable polymer film comprising Eu 31 (4f 6 ) ions in an inorganic-organic hybrid exhibits stimulated light emission over the photon centers. 12,13 This type of light-emitter repre- sents a new class of materials that combines the characteris- tics of both the light-emitter and the host of an integrated system applicable in a wide range of optical technologies. 14,15 In this study, we selected a co-polymer poly(vinylidene fluo- ride–hexafluoropropylene) [P(VDF-HFP)] as a host material doped with Eu 31 ions for enhanced piezoelectric response and good optical properties. P(VDF-HFP) is selected due to its good mechanical properties with excellent film forming ability, flexibility, cost effectiveness, chemical stability, and resilient weathering characteristics. 16,17 The piezoelectric performance of P(VDF-HFP) depends on the electroactive crystalline phase content. Generally, a (TGTG conformation)-, b (TTTT conformation)-, and c (TGTG’ conformation)-crystal- line phases are available in P(VDF-HFP). 18,19 Particularly, it is widely accepted that mechanical stretching is required to achieve a polar electroactive b- phase that exhibits piezoelec- tricity after external electrical poling treatment. 20 However, the stretched film suffers from surface and thickness inho- mogeneity, which is unfavorable for device fabrication. In addition, electrical poling steps must be performed carefully, as the film is susceptible to failure due to electrical Additional Supporting Information may be found in the online version of this article. V C 2016 Wiley Periodicals, Inc. WWW.MATERIALSVIEWS.COM JOURNAL OF POLYMER SCIENCE, PART B: POLYMER PHYSICS 2016, 00, 000–000 1 JOURNAL OF POLYMER SCIENCE WWW.POLYMERPHYSICS.ORG FULL PAPER