The Kynix Blog

SummaryIt has been successfully demonstrated that a nanocrystal of of perovskite can serve as a quantum emitter of light, and, when coupled with a nanophotonic cavity, can dramatically improve the efficiency of the light emission by an international research team from the University of Maryland and ETH Zurich in Switzerland.  A new device features perovskite nanocrystals and a series of nanophotonic cavities. The arrows indicate the way that the UV laser used to excite the crystals, and the light  the crystals produce, move in and out of the device. Described in the Journal Applied Physics Letters ,the resulting device and method could be used to build nanolasers and optical devices that exhibit much faster response times than currently possible. Previously, there have been other quantum emitting materials that have been coupled to nanophotonic cavities. In this area, epitaxial materials such as quantum dots have garnered the most research interest. Distinct advantage to using PerovskiteHowever, the researchers believe there are some distinct advantages to using perovskite nanocrystals instead of epitaxial materials, which involve the fairly complex deposition of a crystalline layer on a crystalline substrate.Instead of the epitaxial techniques, the perovskite nanocrystals are synthesized using inexpensive colloidal chemistry techniques. This also makes it possible for these crystals to be placed on a broad range of substrates using simpler solution-deposition techniques when they are coupled to various photonic structures. The other main set of advantages for perovskites in light-emitting applications relates back to why they have become such a darling in photovoltaics: their optical and electrical properties. Perovskites exhibit a slow non-radiative decay rate and low densities of carrier-trapping defects, which contributes to their high photoluminescence efficiency at room temperature.In addition, the emission spectrum could cover the whole visible range by controlling the size and material composition, especially for the blue-green wavelengths that are otherwise difficult to access. The device operates by exciting the coupled system using a UV laser. This excites the perovskites to a higher energy level. Within a nanosecond, the exciton (an excited electron-hole pair) will decay to its ground state while transforming its energy in the form of an emitting photon. The cavity introduces more decay channels to the emitting materials, so a majority of the photons are coupled into the cavity and form the standing mode of the cavity. Finally, the researchers are able to detect the photons leaking away from the cavity, which is the emission signal. Difficult metThe problem that previous attempts have encountered in working with nanocrystal perovskites has been the material quality. “We need emitters with good photostability, so it can hold the performance when coupling to the cavities, said Yang. “Our collaborators from ETH provided perovskites that make this coupling possible.” In addition to nanolasers and faster optoelectronics, Yang believes the device they have made could increase the efficiency of existing perovskite emitting devices, such as LEDs, which could open up real-world applications in efficient illumination and displays. Before these aspirations can be realized, Yang concedes that they will need to further improve the performance and stability of the material itself. Second, it would be better to excite the material electrically rather than optically for practical use.Yang will try to realize similar devices spanning the whole visible range and the next step it to find ways to further improve and stabilize the performance and also utilizing electrical gates to excite the material in devices. Article source: Applied Physics LettersArticle edited by kynix 

SummaryWe know that empty batteries are easy to recognize.However,it is much more complicated to know the charge status between full and empty.A complete new approach with ultrasound pluses offers a precise and simple method. Batteries are used in many "mobile" technologies,and that is why it is the snag in "mobile" technologies. Like smartphones,drones,or electric cars-in many cases he time between battery charges is much too short for many people. This is why it is important to determine the exact state of charge. But this is more complicated than you would imagine. Currently, battery management systems (BMS) carry out the necessary measurements. They calculate the state of charge for each cell based on the parameters current and voltage.  However, since the calculations are partly based on standard values, they reflect the current state only approximately. In particular, this is very inaccurate in case of frequent partial charges. The battery management systems also consume some of the energy that was actually to be used for the next song or mile. About the aboving picture:Sensors with 1 cm and 2 cm diameter to measure the state of charge of the battery Battery Management with UltrasoudIn the future this will be more reliable, more energy saving and cheaper with sensor systems that are being developed in the SoCUS project at the Fraunhofer ISC. They measure the density of the negative anode with the help of ultrasound pulses. This changes as the state of charge of the cell changes.The method has several advantages: there is a direct linear connection between the state of charge and the measurement signal. This makes the evaluation simpler and more precise than with the technologies currently in use.The new battery sensors can be easily integrated into existing systems.One evaluation unit can monitor several battery cells simultaneously and measures the state of charge only during charging and discharging. The fact that this system does not check the charge continuously saves energy and, consequently, costs.Since the ultrasound signal correlates directly with the mechanical properties of the cell, all aging processes are taken into account better. This allows more accurate statements to be made about the current remaining capacity and, hence, the performance.  About the above picture: Principle of the state-of-charge estimation by ultrasonic pulsed excitations: A RCN-pulse transmitted through the cell gives rise to two wave packets (wave I and II), where the slower (wave II) ones' amplitude shows a linear relationship on the state-of-charge. For optimized signal strength of-the-shelf piezo transducers are attached centered on opposite sides of commercial pouch-type cells. Battery Management with All TypesThe new measuring method is suitable for almost all types of battery. However, to date only lithium ion batteries have been tested. In particular, electric vehicles should benefit from reliable recording of the battery charge status. After all, the distance covered between charges is the key factor for further development. But reliable monitoring of the state of charge is also important for drones that monitor industrial plants and wind parks or that manage agricultural land. The ultrasound method could be especially profitable for stationary storage systems with a large number of connected battery cells. A sensor that works only when required and records the state of charge of several cells simultaneously can save energy and also costs. In this application, flame retardant battery types are often used where the state of charge cannot be determined accurately with current methods. The new method could extend existing measurement methods of battery management systems in the future, especially also in electric mobility with a reliable, energy-saving, inexpensive variant. 

SummaryAs is known,one of the main barriers to a wider adoption of OLED technology resides in its lack of efficiency compared to fluorescent lamps or Light-emitting diodes(LED).  The SOLED project hoped to solve this problem using chiral organic semiconductor structures. The difference is undisputable: when put side by side with an LED display (display modules), its OLED counterpart will stand out thanks to its sharper images, better contrast and crisp colours.  BodyEnergy efficiency, however, is a key concern for consumers, and OLED is still lagging behind other technologies in this regard. In fact, the only type of display it can top is LCD, but only marginally.To solve this problem, the Weizmann Institute kicked off the SOLED (Chiral organic semiconductor structures) project in January 2016. They aimed to tackle the OLED efficiency problem at its source: ‘The low efficiency of OLED technology is a result of low light emission yield due to the formation of triplet electronic states, in which the two electrons have the same orientation,’ explains Prof. Ron Naaman, coordinator of SOLED.The project’s plan was to use electrons’ spin control with a view to reducing the probability of producing triplet states. This is known as the spin-LED/OLED concept: electrons injected into and from the light-emitting species have a predetermined spin, which helps avoid the formation of ‘dark’, non-emitting triplet states. The team had already benefitted from past experience in this field. They could capitalise on their earlier research on the Chiral-induced spin selectivity (CISS) effect, and proposed to develop chiral organic semiconductor structures to control the spin state of injected electrons and holes in OLEDs.As they initiated the SOLED project, they expected this effect to be able to increase the energy efficiency of OLED devices by a factor of four. Prof. Naaman said "The chiral-induced spin selectivity effect is supposed to allow full control of the electrons’ spin orientation by ensuring that the electron that leaves the emitting molecule has the same spin orientation as the electron entering into the molecule." "Whilst the concept was successfully demonstrated in principle, the team quickly realised that further research would be required to reach their objective. In collaboration with the group of Richard Friend from Cambridge and E. W. (Bert) Meijer from Eindhoven, we could demonstrate our ability to affect the spin orientation in the OLED, but the efficiency of the process was not very high." . "The reason for it is the organisation of the molecules in the OLED. Now, we pursue this work with our collaborators towards better control of material organisation." Until this problem is solved, the team has had to postpone the pre-commercialisation measures they had originally planned for. However, Prof. Naaman is still hopeful that the technology will help OLED technology spread throughout European homes in the form of flexible light emitters. He also underlines the realisation that material organisation is the key factor in achieving spin control as a major outcome for the project. At the end,Prof. Naaman concluded:"We intend to study molecules that self-assemble into three dimensional organised structures, like micro-crystals. We hope to do that under either the FET-OPEN programme or other specific programmes." 

SummaryPublished in the Joural Nature Materials in Nov.13,2017,reaearchers from Princeton University,the Georgia Institute of Technology and Humboldt Uniersity in Berlin is pointing the way to possibly more widespread use of organic electronics. Their research focuses on organic semiconductors,a class of materials prized for their applications in emerging technologies such as flexible electronics, solar energy conversion, and high-quality color displays for smartphones and televisions. In the short term, the advance should particularly help with organic light-emitting diodes that operate at high energy to emit colors such as green and blue.  Body“Organic semiconductors are ideal materials for the fabrication of mechanically flexible devices with energy-saving low-temperature processes,” said Xin Lin, a doctoral student in electrical engineering at Princeton and the lead author. “One of their major disadvantages has been their relatively poor electrical conductivity. In some applications, this can lead to difficulties and inefficient devices. We are working on new ways to improve the electrical properties of these organic semiconductors.” Semiconductors, typically made of silicon, are the foundation of modern electronics because engineers can take advantage of their unique properties to control electrical currents. Among many applications, semiconductor devices are used for computing, signal amplification and switching( signal switches ). They are used in energy-saving devices such as light-emitting diodes and devices that convert energy such as solar cells. In the doping process used to make semiconductors their chemical makeup is modified by adding a small amount of chemicals or impurities. By carefully choosing the type and amount of dopant, researchers are able to alter the electronic structure and electrical behaviour of the semiconductor in a number of ways. As the article shows,researchers have developed an approach for greatly increasing the conductivity of organic semiconductors,which are formed of carbon-based molecules rather than silicon atoms. The dopant, a ruthenium-containing compound, is a reducing agent, which means it adds electrons to the organic semiconductor as part of the doping process. The addition of the electrons is the key to increasing the semiconductor’s conductivity. The compound belongs to a newly introduced class of dopants called dimeric organometallic dopants. Unlike many other powerful reducing agents, these dopants are stable when exposed to air but still work as strong electron donors both in solution and solid state. Seth Marder and Stephen Barlow from the Georgia Institute of Technology, who led the development of the new dopant, called the ruthenium compound a “hyper-reducing dopant.” They said it is unusual, not only in its combination of electron donation strength and air stability, but in its ability to work with a class of organic semiconductors that have previously been very difficult to dope. In studies conducted at Princeton, the researchers found that the new dopant increased the conductivity of these semiconductors about a million times. The ruthenium compound is a dimer, which means it consists of two identical molecules, or monomers, connected by a chemical bond. As is, the compound is relatively stable and, when added to these difficult-to-dope semiconductors, it does not react and remains in its equilibrium state. That posed a problem because to increase the conductivity of the organic semiconductor, the ruthenium dimer needs to react with the semiconductor it and then split apart. The researchers looked for different ways to break up the ruthenium dimer and activate the doping, eventually they added energy by irradiating with ultraviolet light, which effectively excited the molecules in the semiconductor and initiated the reaction. Under exposure to the light, the dimers split into monomers, and the conductivity rose. "Once the light is turned off, one might expect the reverse reaction to occur" and the increased conductivity to disappear, Marder said. "However, this is not the case." The researchers found that the ruthenium monomers remained isolated in the semiconductor even though thermodynamics should return the molecules to their original configuration as dimers. The team's hypothesis is that the monomers are scattered in the semiconductor in such a way that it is very difficult for them to return to their original configuration and re-form the ruthenium dimer. They are, according to the team “kinetically trapped." The researchers also discovered that doping was continuously re-activated by the light produced by the device. The light activates the system more, which leads to more light production and more activation until the system is fully activated, Marder said. "This alone is a novel and surprising observation." The work was supported in part by the National Science Foundation and the U.S. Department of Energy. Article edited by kynix   

DescriptionFor everyone,electrical energy is essential. We always trying to get unlimited electrical energy without spending money. Now kynix share a simple design proposed as small wind turbine for home use or low power usage,it requires low initial cost and gives best return in terms of electrical energy. Use the following small wind turbine circuit and setup to charge laptop,to charge electronic gadgets or to electronic appliances in home and outstations.  NoteBefore we start,we should emphasis that we should note:* High voltage caution! This Circuit Involves in operating High voltage handle with extreme care.* Handle the Wind Turbine Generator and Rotor blade as per the Instructions given by manufacturer.  Windmill Generator DesignSmall 12V wind turbine generator is capable of producing alternate energy through wind, the Bridge rectifier and controller rectifies the energy came from wind turbine generator and regulator-battery charger circuit helps 12V/4.5Ah SLA battery to get charging, then Step-up inverter circuit produce high voltage AC enough to operate home appliances.  Schematic of Wind Turbine Generator is as following.  WorkingThere are five stages:  1. 12V Wind turbine generator/Bridge Rectifier Circuit  2. Regulator / Battery charger circuit  3. Inverter circuit using CD4047  4. mosFET Drivers  5. Output Stage 12V Wind Turbine Generator12 Volt wind turbine or windmill available with different watts range, choose depends on your requirement. Bridge RectifierWe know the bridge rectifier converts AC supply into DC and here we used 1N4007 diode as a bridge rectifier element, it converts the energy from wind turbine into Direct Current (DC) supply. Regulator / Battery ChargerThe LM317 adjustable three terminal Positive voltage Regulator used here and it can give output voltage range from 1.25 V to 37 V with more than 1.5A current rating. final output from the regulator is given to 12/4.5Ah SLA Battery, this Battery provides DC bias to the inverter circuit. Regulator LM317 output voltage Vout can be obtained asVout = 1.25V *(R2/R1+1) R2 => R2+VR1 for given inverter circuit.Inverter Circuit using IC CD4047 (Switching Pulse Oscillator) Monostable / Astable multivibrator  CD4047 used here to produce switching pulse, This IC works in low power and available in 14 pin Dual in line package. It provides full Oscillation output F at Pin 13, 1/2 of oscillation at Pin 10 as Q and Pin 11 as Q’. each output pin gives 50% duty cycle.f = 1/8.8RCHere R => R4+VR2 and C=> C3. by using this formula we can obtain frequency output at pin 13. For pin 10 and 11 the formula changes as f=1/4.4RC. MosFET driversIRF540 N Channel power mosfet from vishay siliconix used as a switching drivers for this inverter circuit. It gives fast switching, and have high operating temperature characteristics (175ºC). Output StageMain part of wind turbine generator is output stage, here transformer X1 is used in reverse with specifications as 230V primary, 9V-0-9V / 1.5A secondary winding center tapped transformer. MOV (Metal oxide Varistor) protects electronic device connected at output. Wind turbine generator output voltage is directly fed into LM317 positive Regulator circuit and it is adjusted to give 12 volt output and Battery connected to this bias through (3A, 50V) Schottky diode. The CD4047 IC is connected and configured as Astable multivibrator, When we turn ON SPST switch this circuit starts oscillation. Output Q and Q’ are directly fed into switching power mosfet IRF540 & drives X1 transformer secondary winding, here the current flow occurs particular duration and not for particular duration. So varying electromagnet induced and primary winding coil produce EMF, hence we get Alternating current output. Depends on the count of winding and switching frequency output Voltage/Frequency get varied. 

SummaryDo you think that electornics and light one day can go well toghther on a standard‘CMOS' chip one day? It's reported that researchers have succeeded in introducting a light connection into the heart of a semiconductor chip a few days. In this way,two circuits can communicate.Or: the worlds of electronics and photonics are connected. BodyWhat is particularly attractive is researcher of the university of Twente--Satadal Dutta's solution--A light connection into the heart of a semiconductor chip. There is no special materials or manufacturing processes are needed: the light comes from silicon. The light source, detector and the light channel can be made using the technology that is used to make the electronic circuits. Fully optical circuits are available nowadays, but they use materials like indium phosphide and gallium arsenide, which can't easily be combined with the CMOS chip processes used for semiconductor chips you'll find in today's smartphones.  Connecting WorldsThere is a predictions say that all-optical circuits may become the‘new electronics'. In the transition from electronic to optic circuits, hybrid circuits, like the one Dutta designed, could play an important role. Satadal Dutta (1990, Barrackpore, India) did his PhD research in the Semiconductor Components group of Prof Jurriaan Schmitz, together with the Integrated Circuit Design group of Prof. Bram Nauta. Dutta defended his thesis 'Avalanche-mode silicon LEDs for monolithic optical coupling in CMOS technology' on 8 November. It was supported financially by NWO-TTW in The Netherlands and by NXP Semiconductors.  Avalanche LEDThe alternative would be: make a LED out of silicon. And that's the problem: silicon only emits a tiny amount of infrared light, while a detector made out of silicon needs visible light. They are talking and listening at different wavelengths. Dutta therefore chooses a remarkable way out: connect the LED reverse. At low voltages, there's no current, but at a voltage that is high enough, there will be a small current that amplifies itself like an avalanche. In this 'avalanche mode', the LED will transmit visible light. Using the same process, the light detector, as well as the light channel in-between can be made. Thanks to the special comb structure that Dutta designed, the light source gets more uniform and energy efficient. IsolationAn optical link on a chip is a good way to 'galvanically' isolate two circuits from each other. This is often necessary in cases where one circuit is a low-voltage and low-current one, while the other is a high-power circuit. They should be connected, but not by conducting wires, for reasons of safety. A classic transformer is an option then, but an optical connection is often used as well. Until now, this is a separate 'optocoupler', which is large and has a limited bit rate. Dutta's new solution is much more compact as an alternative: it total, it is just a few tens of microns and it offers the protection that's needed. Compared to optical channels in full-optical circuits, the energy consumption is relatively high, as there is quite some scattering of light. On the other hand: designing the electronics around the optical link in an efficient way, the amount of light needed for a successful connection, can be kept to a minimum.