Energy harvesting is one of the most promising research areas to produce sustainable power sources from the ambient environment. Which found applications to attain the extensive lifetime self-powered operations of various devices such as MEMS wireless sensors, medical implants and wearable electronic devices. Piezoelectric nanogenerators can efficiently convert the vastly available mechanical energy into electrical energy to meet the requirements of low-powered electronic devices. Among the piezoelectric materials, poly (vinylidene fluoride) (PVDF) and its copolymers are extensively studied for the development of energy harvesting devices. Due to the outstanding properties such as high flexibility, ease of processing, long-term stability, biocompatibility makes them a promising candidate for piezoelectric generators. Nevertheless, compared to piezoceramic materials, PVDF based generators produce lower piezoresponse. Over the last decades, tremendous research activities have been reported to endorse the performance of PVDF based energy harvesters. This review article mainly focused on the recent progress in the performance improvement with processing methods, piezoelectric materials, different filler loading. The new developments and design structures will lead to an increase in piezoelectricity, alignment of dipoles, dielectric properties and subsequently enhance the output performance of the device. Electronic circuits play a vital role in energy harvesting to efficiently collect the developed charge from the device. Here, we have proposed a detailed description of the electronic circuits. Also, in the application part deals with the recent progress in flexible, biomedical and hybrid generators based on PVDF polymers.

Small-scale energy harvesting to power self-powered electronic devices is tremendously increasing. In this context, the ability to combine thermal and mechanical energy harvesting using smart materials deserves more attention for further study. We have presented the feasibility of using P(VDF-TrFE) piezoelectric polymer coupled with NiTi shape memory alloy (SMA) to harvest both mechanical and thermal energy in simple scalable devices. A novel hybrid composite consisting of SMA, and P(VDF-TrFE) has been developed without any complex composites or patterned structures, which couples the piezoelectric effect of the poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) and the shape memory effects of NiTi SMA. We have also fabricated a multi-layer SMA/PEN/P(VDF-TrFE) device using epoxy as an interface and bonding layer. During bending, the P(VDF-TrFE) device with an active area of 3.68 cm2 generated an output voltage of 8 V and an output power of 6.25 µW. When coupled with NiTi SMA to create a hybrid composite thermoelectric material, the device can convert the phase change associated with SMA, and thus thermal energy is converted to mechanical energy and finally into electrical energy. The SMA/P(VDF-TrFE) hybrid composite produced an output voltage of ∼2 V for one cyclic heating and cooling of the device. This is a promising approach for the further development of coupled hybrid energy harvester devices for the powering of small-scale electronic devices such as sensors, MEMS, or biomedical devices.

Single-electronic transistors (SETs) are considered as the attractive component for the next generation of transistors due to their ultrasmall size and low power consumption. Because SETs with single island cannot work at high temperature normally, more researchers begin to carry out research on the SETs with N-dimension multi-islands. In this paper, we introduce a new architecture of single-electron memory; ideally the memory should operate in combination of SETs with a nanowire of two-dimensional regular array of multiple tunnel junctions (MTJs). This structure is analyzed and studied with Monte Carlo simulator, SIMON. The Coulomb blockade effect and thermionic effect play an important role in carrier conduction in the system at room temperature. Nanowire MTJs are used as an electrometer to sense the memory-node charge. The well-defined parameter in tunnel junction circuits helps to obtain the charging of single electrons in these circuits at room temperature.

In this paper we report charge trapping effect in a few number of nanocrystals silicon (2-4 nc-Si) embedded in SiO 2 layer tunnel oxide of small area single electron photodetector (Photo-SET or nanopixel). The device detection time which estimated using capacitance versus time (C-t) measurements gives us a detection time about 350 s at T = 280 K. Capacitance versus voltage (C-V-T) measurements as a function of temperature confirm the presence of thermally activated trap centers localized at the tunnel oxide layer (trap activation energy: Ea ∼ 0.41 eV and capture section: σ ∼ 1.72 × 10 −17 cm 2 ). It is found that traps contribute to determine the detection process state where a threshold voltage shift of 60 mV at T = 280 K which corresponds to the trapping of one electron in the nc-Si dot. This process is probably due to the dominance of tunneling of electrons from traps level to the poly-Si/SiO x = 1.5 interface via the nc-Si. The Photo-SET estimated detection time is influenced by oxide traps.