Shocked! Only two months, published a Science, more than 10 sub-Journal / AM / JACS- Canada academicians Professor Sargent highlights achievements
Professor Edward H. Sargent is the Royal Canadian Academy of Sciences, Canadian Academy of Engineering, Canada\’s chief scientist in the field of nanotechnology, Vice-Chancellor of the University of Toronto, Canada. Mainly in the light emitting devices and energy conversion, energy biosensor catalyst preparation and related research. He not only opened up thein the international (CQDs) conversion of light detection and research, but also focus on the growing prominence of energy shortage and environmental pollution problems through interdisciplinary chemistry, nanotechnology and energy research across theoretical modeling, a aspects developed a new type of green perovskite solar cells (photoelectric conversion efficiency world record holder), on the other hand actively explore and study new catalyst for the production of renewable fuels and chemical raw materials. Professor Edward at the same time continue to actively explore new methods, new materials and new principles, but also pay attention to the transformation of longitudinal research laboratory that can be mass-merchandise, has was founded three technology companies, science and technology and productivity achieved conversion between.
Here, we combed Professor Edward H. Sargent team since 2020 light conversion materials, devices and catalytic in the neighborhood research achievements, including a regular issue, six sub-Journal, 7 Joule / AM / JACS / ACS Nano / Adv.Sci, quite shocking! a: Xiao Bian will be around the following four points. Electrolytic catalyst II. Preparation and application of new colloidal quantum dots III. Perovskite optoelectronic devices Fourth, the other Note: This article only selected Edward H. Sargent academicians as (co) corresponding author of the paper; limited academic standards, selected articles and statements are subject to inappropriate, please criticized the correction.
a. Electrolytic catalyst
1.Science: record time, the ethylene is converted to carbon dioxide!
Electrolytic catalytic CO 2 and a plurality of carbon to CO reduction is expected to slow organicsSolutions currently increasingly prominent energy shortages and environmental pollution problems. General electrolysis catalyst device needs to be provided in an aqueous solution by the electrolysis of water to organic carbon multiple proton, which led to a serious problem: CO 2 in an aqueous solution diffusion poor ability (diffusion in alkaline solution length of only several tens of nanometers), thus resulting in a low current density electrolysis (<100 mA cm -2 ) and a low energy conversion efficiency, at the same time, since the catalytic reaction in the electrolytic gas (CO 2 ) – the solid (catalyst) – liquid (electrolyte) complex three-phase zone, a hydrophilic layer may be corroded catalyst activity at high alkaline electrolyte into the environment, resulting in increased catalytic activity and decreasing hydrogen evolution reaction. Based on this, the University of Toronto Professor Edward H. Sargent joint team Professor David Sinton team design [ 123] capable of decoupling the gas ions and electrons metalliferous – electrolytic ionic polymer composite catalytic system (CIBH) , the electrolysis CO.\’s 2 when preparing a multi-carbon compound current density exceeds 1 a cm -2 , the highest reported so far value. Selection of with hydrophilic -SO 3 – group and a hydrophobic -CF 2 radical polymerization of perfluorosulfonic acid (PFSA ) coated on this catalyst surface is achieved CIBH structure , a hydrophilic group of the surface of the coating layer so as to contact the catalyst with the electrolyte in contact sufficiently wetted, facilitate the generation of protons, and the internal hydrophobic facilitate the passage CO 2 of the transmission. The results showed that only the thickness of the coating layer can be made of 5-10nm CO 2 to to enhance the diffusion length of nearly 400-fold , to the micron level. The structures were applied to Cu and Ag-based catalyst is CO 2 prepared by reduction ofCO, Ag-CIBH Cu-CIBH and current density, respectively, of the catalytic system can reach 400 m Acm -2 , and 340 m Acm -2 , while the original current density of Ag and Cu catalysts were only 54 mA cm -2 and 64 mA cm -2 . On this concept, the design of the 3D Cu- CIBH catalyst system, in 7M KOH electrolyte CO 2 the flow rate reached 50 cm 3 min -1 , the maximum current density of 1.32 a cm -2 , the cathode to improve the energy efficiency by 45%, this technique greatly enhance the catalytic electrolysis CO 2 preparation of multi carbon organics its feasibility iNDUSTRIAL ( \”Science\”: a record rate, the carbon dioxide is converted to ethylene !). Reference:.. De Arquer FPG, Dinh CT, Ozden A, et al CO2 electrolysis to multicarbon products atactivities greater than 1 A cm- 2 [J] Science, 2020, 367 (6478): 661- 666. original link: https: //science.sciencemag.org/content/367/6478/661
2.Nature catalysis: catalyst OH adjusted to achieve selective binding electrolysis ethylene to ethylene glycol ethylene glycol is an important refrigerant monomers and polymers, the global consumption of 20 million tons per year. Currently the industry is the use of ethylene as the main raw material, a high temperature oxide intermediate two-step process to prepare ethylene glycol, which causes a great pollution to the environment (the process will produce one ton of emissions 1.6 tons of ethylene glycol the CO
2 ). With the rapid development of renewable energy technologies, catalysis by an electrolytic method to prepare an ethylene glycol to become gradually replace the current two-step process is the best solution, however, present a major problem now has two: First, production efficiency low; Second-product obtained (acetaldehyde, acetic acid and ethylene oxide) more. Methods To solve this problem, University of Toronto, Canada, Professor Edward H. Sargent team direct doping prepared by a Pd Au-doped nano-dendritic structure the composite catalyst (Pd Au DNT), Pd Au DNT capable of with high selectivity to ethylene glycol electrolysis catalysis . It found by electrolytic catalytic preparation of ethylene glycol The most difficult step is OH Intermediate * C 2 H 4 OH to form ethylene , and OH conventional Pd catalyst higher binding energy (0.74 eV), is not conducive to adhering to the catalyst surface OH * next reaction. After density functional theory, the high energy release of Au (-0.06 eV) OH can be reduced with the binding energy of the catalyst, and experiments show: doped with only 3.2at% Au catalyst of Pd Au DNT electrolysis. Faradaic efficiency catalytic preparation of ethylene glycol is 80%, the local current density reached 5.7 mA cm -2 , at 1.1V, to Ag / AgCl as the reference electrode under conditions of continuous work than 100 its catalytic ability remains substantially unchanged after h, the catalyst Pd DNT Faraday efficiency under the same conditions only about 60% of the local current density is only 2.5 mA cm -2 , less than half of the catalyst Pd Au DNT . Reference:. Lum Y, Huang JE, Wang Z, et al Tuning OH binding energy enables selective electrochemicaloxidation of ethylene to ethylene glycol [J] Natu.re Catalysis, 2020: 1-9 description link:. https: //www.nature.com/articles/s41929-019-0386-4
3.JACS: reducing CO 2 an increased concentration of methane conversion rate of the catalytic electrolysis methane is the simplest structure organic chemicals, cleaning is an important industrial raw materials and fuel. It may be prepared in a large number of organic compounds including methane by catalysis electrolysis, but there is also the preparation of low methane selectivity, Faraday efficiency only about (18 ± 4)%, the production efficiency is greatly reduced. Recently,
the University of Toronto Professor Edward H. Sargent team found that the electrolysis process * CO protons into * CHO (methane precursor) and * CO CC coupled to the occurrence of C reaction 2 of a chemical reaction competition, and * CO concentration in a surface catalyst promotes protonation by reducing * CO, methane selectivity is improved electrolysis catalytic preparation of . Researchers 1M KHCO 3 electrolyte, nano Cu deposited on a porous PTFE as a catalyst system, the effects of different CO 2 Preparation of a selective catalytic electrolysis of methane concentration influences. CO 2 at a concentration of 25%, 50%, 75% and 100% of the test results show that the gas source, at low current density (≤100 mA cm -2 ), FE methane / FEC 2+ value (methane and two-carbon chemical content ratio) hardly with CO 2 concentration change varies, and in the at high current densities (200-250 mA cm -2 ), FE methane / FEC 2+ as the value of CO 2 decreased concentration rises, indicating that inAdjusting CO 2 * CO concentration and thus control the concentration method for preparing methane selectivity can be greatly enhanced. Finally, the CO 2 concentration of 75% and a current density of 108 ± 5 mA cm at Conditions -2 and methane Faradaic efficiency reached (48 ± 2)% , and after 22 h of continuous work efficiency can be maintained at 42%. Reference:. WangX, Xu A, Li F, et al Efficient methane electrosynthesis enabled by tuninglocal CO2 availability [J] Journal of the American Chemical Society, 2020. Original link:. Https: //pubs.acs.org /doi/10.1021/jacs.9b12445
4.Advanced Materials: promoting hydration reaction OER neutral conditions the oxygen reduction reaction in a neutral electrolyte conditions (OER) increased in biological hybrid system prepared feasibility of renewable fuels and chemicals. However, since the neutral solution reactant concentration lower than concentration of the alkaline electrolyte is several orders of magnitude, leading to the current in the OER overpotential neutral solution than 460 mV (10 mA cm
2 Current lower densities). Although recent studies iridium oxide coverage (IrO 2 ), Co base, Ni-based and Mn-based catalysts can reduce the overpotential, but these catalysts can not meet the overpotential is lower than 350 mV and long use life (> 500 h) that request. To solve this problem, University of Toronto, Canada, Professor Edward H. Sargent team and Nankai University Zhang Xiaodan Professor teamwork The hydrated ions incorporated in the catalyst to promote the absorption of water by reducing the policy from the catalyst with oxygen, the reaction of neutral solution of OER overpotential reduced to 310 mV (10 mA cm 2 at a current density) . Studies have shown that improved adsorption catalyst with water can improve the performance of the reaction in neutral OER, two kinds of hetero ion composite catalyst researchers prepared: one containing the Ni-Fe Mg ions promote hydration -Mg (HEP) catalyst , further containing Ba ions inhibiting hydration of Ni-Fe-Ba (HEL) catalyst. In the CO 2 saturated 0.5 M KHCO 3 solution for three-electrode linear sweep voltammetry (the LSV) polarization test results show that compared to HEL catalyst, the HEP-type catalyst at 10 mA cm 2 at a current density of only overpotential of 514 mV. The HEP catalyst supported on Au wrapped Ni foam which OER reaction overpotential reduced to 310 mV, a continuous 900 h testing process, faraday efficiency remained within the range of 98% ± 2%, greatly enhance the energy utilization. Reference:. WangN, Cao Z, Zheng X, et al Hydration-Effect-Promoting Ni-Fe OxyhydroxideCatalysts for Neutral Water Oxidation [J] Advanced Materials, 1906806. description link:. Https: // onlinelibrary .wiley.com / doi / 10.1002 / adma.201906806
II. Preparation and application of new colloidal quantum dots
1.Nature Communication: series colloidal quantum dots modified method for a solar cell
colloidal quantum dot (CQDs) with precise dimensions and characteristics of the chemical structure of an adjustable bottom, has important applications in the field of photovoltaic. For example, in terms of energy, the surface properties and structure of the control device CQDs can improve the diffusion length of carriers in turn prepared high power conversion efficiency (PCE) of the solar cell. However, in the preparation of uniform structure CQDs intrinsic device discovery: Although CQD extraction and transport the carrier has advantages, but because of the hard surface CQD highly efficient and stable passive, and therefore the intrinsic homogeneous structure of the device It has not exceeded the performance of the device plane. When doped fundamental reason is that the ligand modification on a large sterically hindered, resulting in a large number of surface defects. And different ligands modified ink CQDs poor compatibility will lead to aggregation CQD mixed together in the preparation of thin film solar cells, thus affecting the performance of the photovoltaic device. In view of this, University of Toronto, Canada, Professor Edward H. Sargent team and the Korea Institute of Advanced Science and Technology Professor Lih Juann Chen Team researchers based policy series surface modification (CSM), the intrinsic homogeneous structure CQDs block an n-type and p-type ink uniformly distributed CQD prepared, for preparing a thin film solar cell . Wherein, the CSM strategy comprises two steps: an initial first halide (passivation) of CQD surface, and then use the new functionality with weight CQD surface modified to control ink CQD obtained having and the solubility characteristics of a particular doping . The synthetic strategy p-type and n-type while the ink CQD with excellent miscibility and surface passivation, can be mixed to obtain a stable colloidal quantum dots. The intrinsic structure of the film prepared by homogeneous mixing colloid, since the light-excited carriers and transport separated on different physical path has been optimized, the carrier diffusion length and therefore significantly improved, reached 340 nm, compared to before the film produced the highest value CQD pure p- type ink (221 nm) lift 150%, PCE value of the solar cell produced the current CQDs battery reaches the highest 13.3% , and AM1.5G measuredAfter the test conditions (nitrogen atmosphere) 110 h of continuous work only 13% lower. Reference: ChoiM J, de Arquer FPG, Proppe AH, et al Cascade surface modification ofcolloidal quantum dot inks enables efficient bulk homojunctionphotovoltaics [J] Nature Communications, 2020, 11 (1):… 1-9 description link : https: //www.nature.com/articles/s41467-019-13437-2
2. Advanced Materials : surface of the passivation improved stable colloidal quantum point air atmosphere photovoltaic device operation stability
colloidal quantum dot (CQDs) application of a problem on a photovoltaic device (PV) is not currently facing a stable operation in the air, which is because CQDs has a large surface area, it is easily oxidized in the O 2 atmosphere. Study found halide having a large atomic radius, such as iodide, surface passivation may CQDs modified to inhibit oxidation, such as with PbI 2 of the PbS type CQDs be modified photovoltaic device in air after saving 1000h can still maintain the efficiency of 90%. However, in practical application are carried out under field conditions, it should be run at the maximum power point (MPP) the test is performed, and then again to evaluate the performance of the photovoltaic device. For example, PbI 2 Modified CQDs photovoltaic device was tested in a passive state MPP found after the continuous test 50 h in air is only 75% of the available power has been maintained, which is far below previously reported in the literature of 1000 h and 90%. How can we prepare excellent antioxidant properties CQDs photovoltaic devices it? Recently, CanadaUniversity of Toronto large Prof. Edward H. Sargent by a group A second method for modification – in PbI 2 Modified CQDs surface passivation layer further modified Antioxidant KI of more housing, CQDs photovoltaic device was prepared in a continuous operation state MPP (air atmosphere) 300 h may remain after [ 123] 80% of the effective power . KI + PbI 2 combinations of modifications to oxidation inhibiting system significantly better than pure PbI 2 modified system , according to the theory, Pb-O Gibbs free energy (ΔG O PbO = -189.24 kJ mol -1 ) Pb-I is less than the Gibbs free energy (ΔG O PbI2 = -173.59 kJ mol -1 ), thus O 2 after the invasion, PbI 2 is oxidized to PbO, PbS colloidal inside quantum dots are oxidized to PbSO 3 and PbSO 4 ; and K and I stronger binding (ΔG O KI = – 322.29 kJ mol -1 is less than ΔG O K2O = -240.58 kJ mol -1 ), is not easily oxidized, while the density Functional theory (DFT) is calculated KI stronger protective effect of S CQDs site. It was found that 0.02M of KI to enhance antioxidant capacity CQDs maximum film photovoltaic device prepared absorption spectrum after treatment also remains substantially unchanged in air at 85 ℃, the instructional material is not oxidized; added KI addition to the improved antioxidant capacity of a photovoltaic device, but also to improve the carrier lifetime of the material (1.2 fold increase), current and charge carrier mobility external quantum11.4% efficiency (EQE), and thus its power conversion efficiency (PCE) also from a pure PbS CQDs device to a 12.6% increase. Reference:. ChoiJ, Choi MJ, Kim J, et al Stabilizing Surface Passivation Enables StableOperation of Colloidal Quantum Dot Photovoltaic Devices at Maximum Power Pointin an Air Ambient [J] Advanced Materials, 2020:. 1906497. original link: https: //onlinelibrary.wiley.com/doi/10.1002/adma.201906497 3.Nano Letter:
emission angle adjustable colloidal quantum dot laser transmitter [ 123] solution processable colloidal quantum dot (CQDs) having a higher fluorescence quantum yield and better light stability, etc. so as to have the advantage of an important potential in the field of the coherent light source. However, due to the excitation light receiving CQDs electron – hole recombination energy is transferred to the third charge carriers, rather than as a photon emission, leading to the loss of non-radiative Auger, resulting in lower emission efficiency. Strategy currently generally employed is prepared CQD putamen structure nonradiative Auger suppressed losses because of the wide-gap case that the addition CQD carriers of electrons and holes in the case of reduced coupling are spatially separated to increase the nuclear optical gain outer shell (> 10 monolayer) bulky structure can also be excited by light. However, the projected display, remote sensing, optical inter-chip applications neighborhood, often require steerable laser, and transmitter CQDs unfortunately difficult to do this. For this application problems, University of Toronto, Canada,
Professor Edward H. Sargent team joint United StatesNorthwestern University Prof. Teri W. Odom group using the lattice plasma nano high symmetry, the excitation laser emitter CQDs prepared adjustable angle. Researchers first pitch on the Si board 400 nm, the diameter and height of 70 nm and 60 nm Ag nano-pillar 2D lattice, and then coated on the matrix layer a thickness of 90 nm was prepared containing shell (CdS) – CQD core (CdSe) excitation layer film structure. This is close to the lattice point Δ hybrid resonance waveguide lattice surface (W-SLR) mode will benefit from the angle of laser light emitted abnormality, will be due to the optical feedback, the laser beam from the side of the W-SLR band mode is azimuthal polarization and of annular shape. By changing the periodicity of the lattice, since the adjustment can overlap other high symmetry points (or Gamma] M) and a CdS shell excitation light generating laser control of different angles. At the same time, by simply increasing the thickness CQDs film can be obtained to avoid the higher order mode W-SLR intersect in the photonic band structure, and further extends the cavity mode is selected, can be achieved at any angle of the laser emission. Reference: Guan J, Sagar LK, Li R, et al Engineering Directionality in Quantum Dot Shell Lasing UsingPlasmonic Lattices [J] Nano Letters, 2020. Original link:.. Https: //pubs.acs. org / doi / 10.1021 / acs.nanolett.9b05342 4.ACS Nano:
a controllable polarization mode quantum dot / laser transmitter plasma coherent polarization Everbright large promote the development of photonic technology has important applications in microscopy, biological physics, quantum optics and other fields. Most rely on laser technology bulky polarizing optical element is difficult to implement applications in the micro-chip device, it is possible to transmit efficiently, having the desired polarization mode light source and an nanoscalePieces now become the focus of research in this field. Wherein colloidal quantum dots (CQDs) having high workability, etc., and fluorescence quantum yield of the solution phase, is a promising nano luminescent medium, but there is also a simple device is difficult to CQDs effective laser polarization control. And plasma nanoparticles (NP) as a special kind of matrix nanostructures surface lattice resonance (although SLRs.) Wherein the diffractive coupling between the NPs produced with high quality factor and constrained sub-wavelength mode. Adjusting the belt structure SLRs mode by controlling the refractive index, polarization of light and the geometry of the lattice, such that the excitation wavelength can be adjusted in real time, in order to achieve multi-mode switchable laser emission. By combining plasma NP lattice and CQDs advantage, University of Toronto, Canada,
Professor Edward H. Sargent joint team of Northwestern University Teri W. Odom Professor group preparation of a plasma-based metal and CQDs NP, controls the laser polarization modes by a quantum dot laser plasma near field coupling . On the Ag NP-containing matrix layer coated CdSe-CdS core – shell structure CQD film, the surface of the high refractive index optical waveguide lattice resonance Ag NP lattice film formed CQD initiated together form a waveguide having a hybrid surface resonance lattice structure (W-SLR) mode. This W-SLR structure such that the laser emission mode plane wave mode in converter zero, may be implemented transmit in any radial orientation and polarization CQD by controlling the thickness of the film to achieve a micro material capable of generating the desired polarization mode system from nanometer laser source to a desired quantum communication and quantum information applications body / plasma hybrid system design offers the prospect. Reference:.. Guan J, Sagar L K, Li R, et al Quantum Dot-Plasmon Lasing withControlled Polarization Patterns [J] ACS nano, 2020. Original link:https://pubs.acs.org/doi/10.1021/acsnano.9b09466 Third, the perovskite photovoltaic device
set records! inverted perovskite solar light conversion efficiency up to 22.3% inverted with respect to the conventional metal type, metal / perovskite halogen, a hole transport layer and an electron inversion / halogen perovskite device has a more stable state and long life when used in a solar cell and therefore the neighborhood has been widely studied. However, the optical power loss of voltage non-radiative recombination of the charge carriers results in causing an inverted solar cell perovskite low power conversion efficiency (PCE), according to the current authentication result, the perovskite-type inverted solar cell can only reach a PCE 20.9%, well below the 25.2% conventional highest. How to further enhance the value of the inverted type perovskite PCE is a question of better practical application of solar cells to be needed to solve. Current research indicates that caused by an internal defect perovskite crystal trapping states of charge carriers is non-radiative recombination, that is the source of the low value of PCE, solve this problem, recently University of Toronto,
Edward Professor H. Sargent King Saud University of Science and Technology joint team Professor Osman M. Bakr team jointly study the use of alkyl amines (AALs) small molecules be prepared through the perovskite to the surface of the grain boundaries and in situ formed self-assembly method for modifying, when the arrangement by promoting highly oriented perovskite grain growth and reduction of defects to significantly improve inverted perovskite PCE ore after the solar cell, reached 22.3% (in the testing result of 23%), and at maximum power to run over under simulated AM1.5 illumination condition that 1000 hours efficiency is almost no decline. In Cs 0.05 (FA 0.92 MA 0.08 ) 0.95 Pb (I 0.92 Br 0.08 ) 3 Preparation of perovskite-type inversion process, the anchor amino AALs perovskite crystal grains held on the alkyl chain hydrophobic tail filled at the interface of the grain and stable under van der Waals forces, the presence of the inclined limits AALs perovskite crystal grains in the growth process of the particles, the final forming a (100) oriented film led, which is lower than the defect density of randomly oriented film. As the growth, having long hydrophobic chains AALS eventually is discharged to the surface of the perovskite thin film, increase the hydrophobicity of the film. The results show that the anisotropic perovskite section having electronic properties so that the film will turn reduces the overall orientation of the crystal defects, which provides an important theoretical foundation for the design and subsequent preparation of excellent and stable inverted perovskite solar cell. Reference: Zheng, Xiaopeng, etal \”Managing grains and interfaces via ligand anchoring enables22.3% -efficiency inverted perovskite solar cells.\” Nature Energy (2020):. 1-10 description link:. Https: // www .nature.com / articles / s41560-019-0538-4 2.Nature Materials:
perovskite depth analysis component – the relationship between performance [- structure 123] by optimizing the currently active layer perovskite element content, it can be the most outstanding performance perovskite solar cell energy conversion efficiency of 25.2%. Usually the active layer composed of a perovskite of the formula ABX3, where part A is methylamine (MA) combination of metal cesium (Cs) and formamidine (FA), X is a halogen moiety is a combination of I and Br. In principle Cs and FA is an essential component forming a stable perovskite structure, and the MA part is optional. But the results of the experiment show that only when the groupTime division containing at least 5% of MA, the perovskite that has the excellent energy conversion efficiency. How to understand and grasp the different components on the crystal structure, thereby affecting the relationship of the material properties of perovskite materials, for the preparation of new and more excellent performance perovskite material having an important role in guiding. Based on this, the University of Toronto Professor Edward H. Sargent
team and MIT William A. Professor Tisdale team using the transient photoluminescence microscopy (TPLM) in combination with the theoretical model, the explored depth perovskite material component – structure – the relationship between performance, found inside the single crystal perovskite material contained diffusivity and structure independent of the composition of the carrier; composition significantly affect the behavior of the internal diffusion of carriers within the film of the chemical constituents have a polycrystalline perovskite material: CsFA MA of perovskite-type calcium-free carrier diffusion CsMAFA rate of carrier than the perovskite-type diffusion flow rate (0.034 cm 2 s -1 ) an order of magnitude. Researchers diffusion of carriers between the different kinetics of calcium component perovskite made intensive studies, found that with respect to the perovskite-type CsFA, CsMAFA perovskite containing more cations not only have a more long carrier diffusion length, which has a long carrier lifetime, derived mainly from the low potential barrier between the interior of the grains, according to the detection EDX and XPS analysis, CsFA perovskite higher potential barrier from its non-uniform crystal, resulting in inconsistent internal and external elements in crystal grains, is not conducive to forming a carrier diffusion \”shell core structure.\” Reference: Saidaminov MI, WilliamsK, Wei M, et al Multi-cation perovskites prevent carrier reflection from grainsurfaces [J] Nature Materials, 2020:.. 1-7 description link:. Https: //www.nature. com / articles / s41563-019-0602-2 3.Nature Photonics: lifting the perovskite quantum dot LED luminous efficiency
The organic / inorganic hybrid perovskite ( QDIP) is a combination of excellent charge transport characteristics and new composite perovskite adjustable band gap of the quantum dot, the generated high brightness, high efficiency light source in the infrared night vision, optical communication, and bio-medicine field It has important applications. However, in the conventional system QDiP, perovskite metal halide rapid and uneven carriers led to efficient emission disadvantageous uneven charge accumulation, a high current and high injection problems such as Auger recombination. Further, in order to add a large amount of high-brightness light emitting quantum dot (QD) in the LED device runtime phase separation occurs, resulting in a poor passivation effect and ineffective energy transfer route generated, which is also detrimental to efficient light emission. In view of this, the University of Toronto Professor Edward H. Sargent
team with Professor Jiang Tang Huazhong University of Science and Technology team jointly developed a solution stabilizer is added to make a stable dispersion PbS QD fast initiator and a perovskite crystal nucleation method, the composite film PbS QD uniformly dispersed in the low-dimensional layered perovskite is prepared (QDLP), exhibits excellent luminescence properties . In this study the authors selected phenethylamine (PEA) as a stabilizer, PbS QD can obtain a highly ordered array of quantum dots passivated multilayer perovskite-based oriented uniformly, and to maintain the solution phase pure quite photoluminescence quantum yield (45%). When the LED device is oriented composite film prepared ultrafast energy transferred to the PbS QD, to avoid the non-radiative recombination inside the perovskite uneven accumulation of free carriers caused. Emission test results indicate that the short infrared wavelength region, QDLP type LED external quantum efficiency (EQE of) reached 8.1% (980nm) , a brightness of 7.4 WSr -1 m -2 , the value40 times the highest value of conventional QDiP system. Reference: GaoL, Quan LN, de Arquer FPG, et al Efficient near-infrared light-emittingdiodes based on quantum dots in layered perovskite [J] Nature Photonics, 2020:… 1-7 description link : https: //www.nature.com/articles/s41566-019-0577-1 4.Advanced Materials: Pb-Sn to simultaneously improve the perovskite defect by blunting the solar cell efficiency and working stability
Pb-Sn perovskite lower power conversion efficiency (PCE) limits the efficient and stable full-Sn-Pb perovskite tandem solar cell (Sn-Pb of PSCs) further development. Studies have shown that introduction of a layered perovskite then combined to form the system efficiency and stability of the 2D / 3D composite structure can improve the battery simultaneously, but experiments have shown that for a pure Pb perovskite structure have a significant effect, whereas for Pb-Sn perovskite, to some extent, although this configuration increases the stability of the battery, but prevents the layered perovskite transport carriers out of the plane, resulting in a low fill factor (FF University of Toronto Professor Edward H. Sargent
为了制备高效且稳定的Sn-Pb PSCs，近日， joint team of Nanjing University Professor Hairen Tan team in the process of preparation of Sn-Pb PSCs , the phenylethylamine (PEA) directly into a cationic anti-solvent using a perovskite thin film surface and an inner boundary edge to reduce defects in situ immobilization trap states of charge carriers, while avoiding the layered calcium excessive formation of perovskite phase, to enhance the transmission efficiency of the charge carriers in comparison with the conventional method such in situ passivation of isopropanol (IPA) processing methodFilm surface defects and blemishes less preparation, the passivation layer is formed having a reducing effect on the inhibition and charge carrier trap states, operating efficiency of the device has been greatly improved. Test results show, Sn-Pb PSCs prepared by the method reaches 79% fill factor and power conversion efficiency of 19.4% , and its operating life than the non-passivated Sn-Pb PSCs [123 ] 200-fold increased , the efficiency of successive working under the test conditions of AM1.5G free fall 200 H , the full performance expected for the perovskite tandem solar cell. Reference: WeiM, Xiao K, Walters G, et al Combining Efficiency and Stability in MixedTin-Lead Perovskite Solar Cells by Capping Grains with an Ultrathin 2DLayer [J] Advanced Materials, 2020:.. 1907058. description link: https: //onlinelibrary.wiley.com/doi/10.1002/adma.201907058 5.Joule: preparation of solvent solute optimization perovskite efficient solar concentrator
solar concentrators (the LSC) can concentrate the sunlight from a large area to a smaller area, thus reducing the consumption of photovoltaic (PV) material, greatly improving the conversion of light energy effectiveness. LSC is a translucent optical plate, wherein the chromophore is embedded in the transparent waveguide, it is first absorbed photons from the incident sunlight, and then re-emits longer wavelength photons. Re-emitted photons are guided to the edge of the LSC, then by the solar cell herein will gather light into electrical energy. Low dimensional perovskite nanosheets (PNPLs) due to the energy funnel multiple quantum well (MQWs) may provide a large Stokes shift and highly efficientPhotoluminescence (PL), has become one of the most potential applied LSC chromogenic material. Since the wavelength of the absorption capacity in the narrow range, Br group PNPLs currently used only 1.5% of the light conversion efficiency (ηopt), development and preparation of a new structure having PNPLs LSC important for improving the conversion efficiency of solar light. University of Toronto
Professor Edward H. Sargent team and King Saud University of Science and Technology Professor Osman M. Bakr team We have jointly developed a the I group PNPLs, 10 × 10 cm size was prepared with the obtained PMMA composite LSC thin film device , the fluorescence quantum yield (PLQY) reached 56%, light 2% conversion efficiency was 1.3 times the maximum value of the previous reports . Compared with the group PNPLs Br, in order to achieve broadband group PNPLs While I have a broader range of absorption wavelengths, but only the current drive member PbI x 2-x to provide the appropriate MQWs the absorption of solar light waves. To this end, the researchers achieved by regulation of the composition and the ratio of solvent and anti-solvent this. It found: high polarity (Goodman contribution value = 26.6 kcal / mol) in DMF with low polarity CB (Goodman contribution value = 3.3 kcal / mol) mixed solvent of group I as precursors prepared PNPLs solvent , the system PbI 2 and to reduce the proportion of active coordination iodide PbI 3 – to increase the proportion of , [123 ] when the ratio of the two solvents is 1: 1, PNPLs finally obtained has the best crystalline MQW configuration and wider distribution, and thus has a broader wavelength absorption range, more efficient energy funnel and higher light-emitting ability of . And a solution containing no CB generated due PbI 2 dominant, resulting PNPLs structurally unstable, and the light emission efficiency is very low. ReferenceDocument:. Li Z, Johnston A, Wei M, et al Solvent-Solute Coordination Engineering for EfficientPerovskite Luminescent Solar Concentrators [J] Joule, 2020. Original link:. Https: //www.sciencedirect.com/science/article/abs /pii/S25424351203003016.Advanced Science: Effect of twin defects perovskite solar cell performance Although the perovskite-based thin-film solar cell maximum power conversion efficiency (PCE) close to the single crystal silicon solar cell substrate, but defects in the perovskite growth is formed between the surface of the grains and grain limits further improved their performance, which is a typical twin defects defect. Theoretical calculation shows that mixed ion density functional perovskites may be formed (111) twin defects, it will cause secondary nucleation Cs-rich and rich phases I, resulting in a hole near the edge of the valence band into the defect, the trap is formed state. However, the specific relationship between the current generation path of twin defects of the solar cell and the value of PCE is not yet clear. To explore this issue clear, the University of Toronto
Professor Edward H. Sargent team and the National Tsing Hua University
Professor Lih Juann Chen [123 ] group in this crystal structure analysis showed that the amount of anti-solvent twin defects perovskite related added, twin defects will reduce the performance of photovoltaic material perovskite direct observation by TEM and binding XRD, and by heteroepitaxial supersaturation nucleation rule crystal twinning defects can be suppressed. Comparative study of the preparation process containing, respectively, 200 – 500 μL CB antisolvent perovskite found antisolvent prepared perovskite low levels in the TEM showed fewer twin defects and exhibits fluorescence in the test longer life carriersCommand (200 μL antisolvent corresponding to 930 ns, 500 μL antisolvent corresponding to 330 ns), and therefore a higher output power and stability of PCE (an SPO) value. XRD analysis showed that the (111) twin boundary tends on (100) plane forming a stress caused by twin defects, leading to a smaller interplanar spacings, diffraction peaks shifted to a high angle. The study explores the link between the twin defects calcium and titanium solar cell performance, and noted that further reduce defect perovskite particles may help to further enhance the perovskite polycrystalline solar cell performance. Reference: Tan CS, Hou Y, Saidaminov MI, et al Heterogeneous Supersaturation in MixedPerovskites [J] Advanced Science, 2020:.. 1903166. link description: https: //onlinelibrary.wiley.com/doi/10.1002/ advs.201903166 Fourth, the other directions: 1.JPCL: the transition dipole moments of the optical Stark effect and the many-body perturbation theory obtained perovskite n = 1,2,3 quantum well reference:. Proppe AH, Walters GW, Alsalloum AYY, et al Transition Dipole Momentsof n = 1, 2, and 3 Perovskite quantum wells from the Optical Stark Effect andMany-Body Perturbation Theory [J] .. The Journal of Physical Chemistry Letters, 2020 original link: https: //pubs.acs.org/doi/10.1021/acs.jpclet. T.9b03349 2 \”Nature Nanotechn.\” Selectively magnetized region of the semiconductor nanorods (first article Corresponding author Professor USTC Yushu Hong) Reference: Zhuang TT, Li Y, Gao X, et al Regioselective magnetization insemiconducting nanorods [J] Nature Nanotechnology, 2020:.. 1-6 description link:. https: //www.nature.com/articles/s41565-019-0606-8 Edward H. Sargen academician Introduction Professor Edward H. Sargent, vice president of the University of Toronto, the Royal Canadian Academy of Sciences, Canadian Academy of Engineering, Ministry of Science and president of the Canadian branch of nanotechnology, InVisage technologies founder, Xagenic co-founder, AAAS Fellow, IEEE Fellow, ACS Photonics deputy editor. Professor Edward H. Sargen is material and photonics neighborhood world-renowned scientists, because of their outstanding contributions to the battery and the light detector semiconductor solar research in the soluble phase treated made, was elected Fellow of the AAAS; because in colloidal quantum contribution of dot optoelectronic devices made elected Fellow of the IEEE; solar cell and its contribution to the ultra-sensitive photodetectors preparation quantum confinement material using the full spectrum made elected Canadian Academy of Engineering. Professor Edward H. Sargen published in Nature and Science and other top international journals multiple papers, are currently already quoted more than 61,894 times (Google data), of which 100 citations of papers more than 100 times.