By applying mechanical strain to the nanowires, the researchers created piezoelectric potentials in them. This potential is used to regulate the transfer of charge and enhance the carrier injection of the LED. The control of this piezoelectric potential for optoelectronic devices is called the piezoelectric-photoelectric effect. This effect can increase the rate at which electrons and holes recombine to generate photons, and enhance the external efficiency of the device by increasing the luminous intensity and increasing the injection current by as much as 4 times.
The professor of the Department of Materials Science and Engineering of the school said that from the actual situation, this new effect can have many effects on the photoelectric process, including improving the energy efficiency of lighting installations. Traditional LEDs generally use structures such as quantum wells to trap electrons and holes, which requires the two to stay close enough for recombination for a long time. The longer the electrons and holes get closer, the higher the efficiency of the LED device. Although the internal quantum efficiency of a general LED can reach 80%, the external efficiency of a traditional single-pn junction thin-film LED is only 3%.
The zinc oxide nanowires in the new device constitute the n of the pn junction, and the gallium nitride film can be used as the p. Free carriers will be imprisoned in this interface area. The piezoelectric-photoelectric effect can increase the luminous intensity by 17 times and the junction current by 4 times when 0.093% compressive stress is applied to the device, thereby increasing the photoelectric conversion rate by about 4.25 times. Under the effect of appropriate external stress, the external efficiency of the new device can reach 7.82%, which greatly exceeds the external quantum efficiency of traditional LEDs.
The LED made by the research team can emit ultraviolet light with a wavelength of about 390 nanometers, but the professor believes that it can be extended to the visible light range in the future and is suitable for various types of optoelectronic equipment. At present, efficient ultraviolet emitters are needed in the fields of chemistry, biology, aerospace, military and medical technology.
The professor also said that this research has opened up a new field of using piezoelectric-photoelectric effect to adjust optoelectronic equipment. Significantly improving the efficiency of LED lighting equipment is expected to bring considerable energy savings, which is very important for the application of green and renewable energy technology. In addition, this discovery can also be applied to other optical devices controlled by electric fields.
Lithium iron phosphate battery has a series of unique advantages, such as high working voltage, high energy density, long cycle life, green environment protection, etc., and supports the scaleless expansion, which can be used for large-scale energy storage after the energy storage system is formed.The energy storage System of lithium iron phosphate Battery is composed of lithium iron phosphate Battery pack, Battery Management System (BMS), converter (rectifier, inverter), central monitoring System, transformer, etc.
In the charging stage, intermittent power supply or power grid will charge the energy storage system. After the alternating current passes through the rectifier, it will be rectified into a direct current to charge the ENERGY STORAGE BATTERY module and store energy.
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