Piezo-photovoltaic micro-energy transducer

П’єзо-фотовольтаїчний мікроенергетичний перетворювачKeywords
Technology use new fuels, renewable and alternative energy sources Energy and Energy Efficiency Semiconductors and semiconductor equipment

The proposed innovation corresponds to the device of simultaneous environment energy conversion due to the combining of piezoelectric and semiconductor properties of the same functional material. Such functional material based multilayer device structure allows implementation of energy conversion by utilization of two parallel principles: 1) piezoelectric conversion of mechanical energy of vibrations and air movements into electric energy, 2) electric energy generation by solar energy conversion using photovoltaic transducers. Zinc oxide is wide-band semiconductor nontoxic biocompatible material with piezoelectric properties and it is used as a single functional material of the device.
Formation of zinc oxide nanoparticles is accompanied by changes of existing properties for unstructured material and appearance of fundamentally new properties. The sudden increase of mechanic-to-electrical transformation effectiveness is occurred due to reduction of effective dielectric permeability and increase of elastic compliance in composites based on it. The dimensional effect begins to appear at reducing of the rod hexagonal structures’ diameter to few-tens of nanometers, leading to the piezoelectric coefficients increase 10 ... 200 times. Additional transformation effectiveness increase is achieved by broadband matching (active impedance transducers) and increasing of effective converting frequency. The reducing to nanometer sizes zinc oxide crystals leads to the appearance of quantum-dimensional effects and accordingly to the substantial change in the photophysical and photochemical properties of the material. Such properties as high electron mobility, high excitonic excitation energy, and high surface area of nanosrtuctured zinc oxide allow the application of this material in hybrid solar cells, which are photovoltaic devices of third generation. The combination of zinc oxide nanostructures and state-of-the-art organic polymer materials allows reducing the price of photovoltaic transducers with simultaneous efficiency upgrading by high efficiency of charges generation. Optical absorption spectrum of the transducer includes the UV radiation, and can reaches up to IR.
Nanotechnological approach "bottom-up" which provides the creation of nanostructures with different morphologies and structures by self-organization at the low-temperature chemical and electrochemical processes without expensive vacuum and other microelectronic technologies is used for the formation of nanostructured zinc oxide. Micro- and nanoimprint, silkscreen process, etc. are used for the formation of the patterned electrodes and other separated layers. The inexpensive flexible polymer materials, glass, textiles are used as the substrate. The synthesis process and materials recycling are environmentally friendly.
Besides perspective application in the innovation, nanostructured zinc oxide is a multifunctional semiconductor material and suitable for the development of other components of electronic systems which are powered: supercapacitors, sensors, transistors, RF and microwave MEMS devices, photodetectors and light emitters of different regions of the spectrum.

Innovative aspect and main advantages:
This innovation offers a comprehensive approach to an efficiency enhancement and decrease in value of environment energy transducers. For the first time the combined structure of nanostructured materials based piezo-photovoltaic micro-energy transducer is offered.
Among other well-known transducers of mechanical energy into electrical energy, piezoelectric transducers have the highest energy density, they are practically feasible and the most promising. The hybrid solar cells are promising photovoltaic devices due to the low cost, the development of new advanced materials, and predictable increases of conversion efficiency in the near future.
The application of nanostructured multifunctional semiconductor material synthesized by nanotechnology approach "bottom-up", which is characterized by lower cost when to compare it to expensive microelectronic technologies (vacuum deposition, photolithography, etc.), and application of low-cost flexible polymer or textile substrates, including a substrates with large area, improves the cost-performance of these devices salvaging compared with analogues.
The efficiency of the piezoelectric transducer increases due to the application of nanostructured zinc oxide because of the "composite" effect and the appearance of a giant piezoelectric size-effect as compared with the classic piezoelectric materials based devices.
Zinc oxide is nontoxic and has a large electromechanical coupling coefficient, while content of a large lead amount (up to 70% Pb by weight) in the most modern and efficient piezoelectric materials such as PZT and PMN-PT limits their manufacturing in large quantities and makes difficulties for recycling. At the same time, polymeric piezoelectrics materials have extremely low piezoelectric coefficients. Additionally for the first time the circuit methods of broadband matching (active impedance transducers) and increasing of effective translation frequency are offered to further efficiency enhancing of the device.
Moreover, the same zinc oxide nanosructures provide efficient photovoltaic conversion and ZnO additional layers form the transparent electrode, extend the absorption spectrum of optical radiation and provide a self-cleaning surface.

Problem solved:
At the present stage of techniques and technologies development an actual problem is a creation of a universal high-performance power supply for micro- and nanoelectronic devices such as wireless sensors, mobile communication devices, medical implants, and wireless electronic systems. Galvanic cells or accumulator batteries are used as power supply for great number of electronic devices, but its application in the case of wireless or medical devices can be expensive, sometimes inconvenient, impossible, and in the case of in-vivo devices even dangerous.
The development of new materials and power efficient technologies for the application of alternative renewable energy sources is a key solution to the universal energy problem of the XXI century. Existing wind power station and photovoltaic solar cells have a high initial cost due to the application of expensive materials and power-consuming technological approaches in the manufacturing and therefore have a long payback period; the stability and efficiency of renewable energy transducers remain low. Solar cells of the second and third generations, which have lower cost, are characterized by low efficiency, instability, and the dye-sensitized solar cells contain volatile organic compounds that pollute the environment.
The proposed transducers can be applied directly as a micro-power power supply of electronic devices and for charging them as well, and as alternative energy transducers of higher power in the future. Simultaneous parallel conversion of light energy and energy of mechanical vibrations can create variations of the proposed piezo-photovoltaic devices to supply the wireless sensors of building structures, vibrating mechanisms, biomedical sensors and lab-on-a-chip, street lighting and architectural lighting in the forms of artificial trees and flowing fabrics (flags), conversion of sea waves energy, movements of the living and nonliving objects etc.
Its application would be cost-beneficial due to the low cost and natural abundance of the raw materials, lower energy consumption and manufacturability of used designing methods and low cost of substrates’ materials. Ecological compatibility, low cost of recycling at end of lifetime and the biomedical applications possibility is provided by non-toxicity and biocompatibility of materials and processes.
The proposed innovative piezo-photovoltaic micro-energy transducer is a universal attractive and perspective device for widespread applications because of combining of the two energy conversion mechanisms.

Development status:
Prototype with favorable lab results

Potential customers, markets:
Potential consumers of innovation are manufacturers and users of electronic devices which require power supply or recharging. The piezo-photovoltaic micro-energy transducer could be the best device for charging of a large number of mobile devices, that fact causes the increasing of the potential consumers number from the users of mobile devices, as well as music players, e-books, navigation systems, which have a rechargeable battery.
It is predicted that the market for environment energy transducers will grow by 30% annually. Declared innovation could be used in the following areas: consumer electronics, industrial electronics, road construction (road markings), military and space technology, healthcare, safety, food industry, environmental protection, agriculture.
Promising applications of the devise are in remote control devices, lighting, monitoring, electronic locks/access control devices, gaming devices, medical systems (wireless inhalers, drug delivery systems, patient monitoring systems, and many others), implantable sensors, charging systems, street, sidewalk and architectural lighting, radio frequency identification, tracking and other portable devices.
The areas that will become a popular application area of micro-power transducers in the construction of wireless sensors of physical quantities or chemicals and radio frequency identification systems with potential customers in the next 10 years include: smart home technology, agricultural security, external security, and so on.