Research on the Recombination Mechanism of Excited Carriers in Perovskite Solar Cells by the Chinese University of Science and Technology of China
Recently, the team of professor Zhao Jin from the Institute of Physics of the University of Science and Technology of China and the International Research Center for Quantum Design of Functional Materials (ICQD) of the National Research Center for Microscale Material Science of Hefei made new progress in the study of the electron-hole recombination mechanism of perovskite solar cells The first-principles excited state dynamics program independently developed by the team revealed the important role of low-frequency vibratory phonons in the electron-hole recombination mechanism. This result is explained by Low-frequency lattice phonons in halide perovskites explain high defect tolerance toward electron-hole The topic of recombination was published in Science Advances. The first author, Chu Weibin, obtained a Ph.D. from the National Research Center for Microscale Physical Sciences in Hefei. Zhao Jin and Professor Wissam A. Saidi of the University of Pittsburgh are co-corresponding authors.
How semiconductor defects and impurities affect electron-hole recombination is an important scientific issue in this field. As early as the 1850s, the famous scientists Shockley, Read and Hall proposed the Shockley-Read-Hall (SRH) model. In this model, they believed that the "deep energy level" in the middle of the energy gap would form electrons- The Hole Recombination Center has been used by many scientists in the semiconductor science community for many years. However, in the SRH model, the electroacoustic coupling effect has not been taken into account, and the electroacoustic coupling is the decisive factor for the recombination of electron holes through non-radiative transitions. In this work, the team of Zhao Jin used the self-developed first-principles excited state kinetics software Hefei-NAMD to study the effect of defects in MAPbI3 of lead-halogen perovskite batteries on electron-hole recombination, accurately considering the electroacoustic coupling , Energy level difference, atomic velocity, electron decoherence, carrier concentration and other factors, found that in this system, the defect will not form an electron hole recombination center, and the SRH model has completely failed. Through quantitative electroacoustic coupling analysis, it is found that due to the low hardness of the material, phonons that contribute to electron-hole recombination are low-frequency phonons with or without defects, and the corresponding amount of non-adiabatic coupling is small, making electron-hole recombination slow. This is why lead-halogen perovskite batteries have many defects, but still have good solar energy conversion efficiency.
In this work, Wissam A. Saidi is responsible for the construction of the defect structure of the system and the calculation of the ground state, and the group of Zhao Jin is responsible for the calculation of the excited state dynamics. This work is another important application of Hefei-NAMD software. Since 2016, nearly 30 academic papers have been published using this software.
This work is supported by the Fund Committee, Ministry of Science and Technology, Anhui Province, etc.
Figure: Defects in lead-halogen perovskite solar cell systems cannot form electron-hole recombination centers. (a) Schematic diagram of recombination of electron holes through defects; (b) Probability of recombination of electron holes in different systems within 2 ns; (c) Probability of direct recombination of electron holes; (d) Probability of recombination of electron holes through defects.
Sectional Door Accessories: motor 220V-380V, control box, spring break device, cable break device , aluminum alloy rope pulley, enhanced shaft bracket, air bag system, duplex enhanced guide wheel bracket.
Detail introduction for above main accessories
1.Motor and controller:
The garage door operator is designed for residential overhead sectional and tilt doors.
The operator memorizes the limit positions and unique braking system that slows the unit down at the end of its travel.
Rolling code remote control with max. 20 pcs hand transmitters.
The operator is equipped with a manual release lever which allows manual operation of the door in case of power failure.
The controller has a security LOCK function which prevents operation of the door from transmitter.
2.spring break device:
Sectional doors are hinged and they bend in the tracks as the door opens and closes. Many of these doors are counterbalanced with extension springs, also designated "stretch springs," and they have seven characteristics. The length is the measurement of all the coils pressed together. This, along with the inside diameter of the coils and wire size - the thickness of the wire from which the springs are made - determine the stretch, the distance the spring is extended - normally half the door height, and pull, the force the spring pulls when stretched its normal length. The type of ends determine how the ends of the spring are mounted. The initial tension is the percentage of pull needed to separate the coils. This is determined by the pitch with which the springs are wound. On sectional garage door springs this is normally 15 percent. For example a 100 pound pull spring requires 15 pounds of weight to separate the coils; when a door is open the two springs will support 15 pounds of door weight without any stretch.
Most extension springs are made of oil tempered wire. These are normally coated or painted. Some springs are made of galvanized wire.
3.able break device:
cable break device ,door hardware
adjustable bottom bracket .
the raw material hot plate
zinc plated
safety device
adjustable bottom bracket
the raw material hot plate
zinc plating
spring safety device ,2" and 3" safety device
once the cable is broken ,this devoice can keep the hurt away from the door falling
4.aluminum alloy rope pulley
Equipment: CNC stamping/punching machine, CNC bending machine, CNC cutting
machine, 5~250 tons punching machines, welding machine, polish machines...
Processed material: stainless steel: copper, carbon steel
Surface treatment: Hot galvanized, polishing
Making process:Stamping, deep drawing,bending, punching, laser cutting,threading,
welding, tapping, riveting, grinding
5.air bag system
It is a safety device. When the door is down to hit something, it will up automatically.
Operation pressure:<3mbar
Battery:CR2032*2
Battery lifetime>1 year
Emission frequency: 315MHZ
Emission power:<10mW
Receiver power source:12V
6.duplex enhanced guide wheel bracket
Determining the right type of sectional door roller for your garage door tracks can be a little confusing, especially when you do not know what you need to look for in a garage door roller. To simplify things, there are two primary things you need to be aware of. First are the actual dimensions of the roller, and second is purpose that you will be using the door for. You can read below about measuring your roller and choosing the right quality of material for your door.
Other Door Accessories,Electronic Door Accessories,Automatic Door Accessories,High Speed Door Radar Detector
Shenzhen Hongfa Automatic Door Co., Ltd. , https://www.hongfadoor.com