A novel potassium-containing quadruple-cation absorber realizes over 20% efficiency and hysteresis elimination for planar perovskite solar cells.

We demonstrate the presence of ferroelectric domains in CH 3 NH 3 PbI 3 by piezoresponse force microscopy and quantify the coercive field to the switching of the polarization of ferroelectric CH 3 NH 3 PbI 3 . For CH 3 NH 3 PbI 3 perovskite solar cell, negative electric poling decreases the net built-in electric field, driving potential and width of depletion region inside the absorber layer, which hinders charge separation and deteriorates photovoltaic performance; while positive poling boosts these electrostatic parameters and therefore improves the charge separation inside the absorber. Low coercive field (8 kV/cm) enables the switching of CH 3 NH 3 PbI 3 polarization during the current density-voltage (J-V) measurement. Forward scan initially activates the negative poling, whereas reverse scan first activates the positive poling, which can lead to the J-V hysteretic behavior. Comparative analysis with a traditional ferroelectric 0.25BaTiO 3 -0.75BiFeO 3 solar cell is conducted to confirm the impact of ferroelectric polarization and J-V scanning direction on photovoltaic performance.

Piezoelectric microelectromechanical systems (PiezoMEMS) are attractive for developing next generation self-powered microsystems. PiezoMEMS promises to eliminate the costly assembly for microsensors/microsystems and provide various mechanisms for recharging the batteries, thereby, moving us closer towards batteryless wireless sensors systems and networks. In order to achieve practical implementation of this technology, a fully assembled energy harvester on the order of a quarter size dollar coin (diameter=24.26 mm, thickness=1.75 mm) should be able to generate about 100 μW continuous power from low frequency ambient vibrations (below 100 Hz). This paper reviews the state-of-the-art in microscale piezoelectric energy harvesting, summarizing key metrics such as power density and bandwidth of reported structures at low frequency input. This paper also describes the recent advancements in piezoelectric materials and resonator structures. Epitaxial growth and grain texturing of piezoelectric materials is being developed to achieve much higher energy conversion efficiency. For embedded medical systems, lead-free piezoelectric thin films are being developed and MEMS processes for these new classes of materials are being investigated. Non-linear resonating beams for wide bandwidth resonance are also reviewed as they would enable wide bandwidth and low frequency operation of energy harvesters. Particle/granule spray deposition techniques such as aerosol-deposition (AD) and granule spray in vacuum (GSV) are being matured to realize the meso-scale structures in a rapid manner. Another important element of an energy harvester is a power management circuit, which should maximize the net energy harvested. Towards this objective, it is essential for the power management circuit of a small-scale energy harvester to dissipate minimal power, and thus it requires special circuit design techniques and a simple maximum power point tracking scheme. Overall, the progress made by the research and industrial community has brought the energy harvesting technology closer to the practical applications in near future.

A novel energy capturing technique for wasted parasitic magnetic noise based upon a magneto-mechano-electric (MME) generator, consisting of piezoelectric single crystal fibers and Ni metal plate in the form of cantilever structure.