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A research group you should know

Time:2021/01/19 丨 source:Fast Silver 丨 visit count:

You should know A group, which can publish a sub-journal in two months

Academician Huang Wei and Professor Chihaya Adachi of Kyushu University in Japan are leaders in the field of optoelectronic materials. Huang Wei was one of the well-known scholars who were very active in the research of polymer light-emitting diode display in his early days. Since the early 1990s, he has been committed to the research of organic optoelectronics, an international frontier discipline developed across multiple disciplines such as physics, chemistry, materials, electronics, information and life, and is building a theoretical system framework for organic optoelectronics. , Realizing the high performance and multifunctionalization of organic semiconductors, and promoting the transformation and industrialization of scientific and technological achievements. He has done a lot of pioneering, innovative and systematic research work. He is the founder and pioneer of China's organic optoelectronics discipline. A large number of systematic and innovative research results have been achieved in the fields of organic optoelectronics and flexible electronics. Professor Chihaya Adachi of Kyushu University in Japan is one of the pioneer researchers in the field of organic electronics in the world. His main research focuses on organic optoelectronics, physical properties of organic semiconductor devices, and organic photophysical chemistry. Professor Chihaya Adachi has been committed to the theoretical research and industrial production of luminescent materials based on Thermally Activated Delayed Fluorescence (TADF). This article has compiled 16 articles published by Academician Huang Wei and Professor Chihaya Adachi in the past 2020, including 15 sub-journals and 1 regular Nature issue.
 
1. Ebinazar B. Namdas, Shih-Chun Lo & Kyushu University Chihaya Adachi Nat. Commun., University of Queensland, Australia: a solid triplet quencher based on cyclooctatriene, which exhibits excellent singlet states in light and electrical excitation Triplet annihilation suppression

 
Triplet excitons are considered to be the main obstacle to the realization of organic laser diodes because the accumulation of triplet excitons can cause significant losses under continuous wave (CW) operation and/or electrical excitation. Ebinazar B. Namdas, Shih-Chun Lo and Chihaya Adachi of Kyushu University of Queensland in Australia reported the design and synthesis of solid organic triplet quenchers, and their dispersibility in bisstyrene-based laser dyes that can be processed in solution. In-depth study. By mixing the laser dye with 20 wt% quencher, the influence on the ASE threshold is negligible, but the singlet-triplet annihilation (STA) is completely suppressed, and the excited state light of the laser dye under CW excitation Stability has been increased by 20 times. We used a small area OLED (0.2mm2) to demonstrate the effective STA suppression of the quencher in the nanosecond range, and provided insights through simulation to gain insight into the STA quenching observed under electrical excitation. The results show that it has excellent triplet quenching ability and excellent solution processability under nanosecond light and electrical excitation. Literature link: Solid cyclooctatetraene-based triplet quencher demonstrating excellent suppression of singlet–triplet annihilation in optical and electrical excitation Nat. Commun., 2020, 10.1038/s41467-020-19443-z
 
 2. Toshinori Matsushima, Atula S. D. Sandanayaka & Chihaya Adachi: Toshinori Matsushima, Atula S. D. Sandanayaka & Chihaya Adachi: Eliminating triplet excitons to suppress the decrease in the external quantum efficiency of organic light-emitting diodes
 

In organic light-emitting diodes (OLED), the large external quantum efficiency drop at high current density is usually caused by the quenching of radiating singlet excitons by long-lived triplet excitons (singlet-triplet annihilation (STA) )). Toshinori Matsushima, Atula S. D. Sandanayaka & Chihaya Adachi, Japan's Science Promotion Agency, adopted a triplet elimination strategy to overcome the above STA problem. In order to construct a model system for triplet removal, the author chose DCNP as the emitter and BSBCz as the host material, considering their singlet and triplet energy levels. In this system, BSNPz effectively cleared the triplet state of DCNP, while the singlet state of DCNP was intact, thereby inhibiting STA under electrical excitation. Therefore, even at a higher current density, the OLED with a 1 wt%-DCNP-doped BSBCz light-emitting layer showed a suppressed efficiency drop. From the perspective of suppressing efficiency degradation, this discovery advantageously provides OLEDs and organic semiconductor laser diodes with advanced light-emitting performance. Literature link: Suppression of external quantum efficiency rolloff in organic light emitting diodes by scavenging triplet excitons Nat. Commun., 2020, 10.1038/s41467-020-18292-0
 
3. Cambridge University Cui Linsong, Richard H. Friend & Georgia Institute of Technology Xian-Kai Chen  & Kyushu University Chihaya Adachi Nature Photon.: Fast spin flip can realize efficient and stable organic electroluminescence from the charge transfer state.

 
The spin reversal from triplet excitation to singlet excitation, that is, reverse intersystem crossing (RISC), is a good way to improve the luminescence of organic light-emitting diodes. However, due to the slow RISC rate (kRISC), equipment stability and efficiency drop are still challenging issues. Cambridge University Cui Linsong, Richard H. Friend & Georgia Tech Xian-Kai Chen & Kyushu University Chihaya Adachi reported a TADF molecule with multiple donor units, these donor units formed a charge resonance type hybrid tristate, resulting in The singlet-triplet energy split is small, the spin-orbit coupling and the triplet dense manifolds close to the triplet state. The kRISC speed in this TADF molecule is as high as 1.5×107/s, which is two orders of magnitude higher than a typical TADF emitter. Organic light-emitting diodes based on this molecule show good stability, high maximum external quantum efficiency (> 29.3%) and low efficiency drops. Literature link: Fast spin-flip enables efficient and stable organic electroluminescence from charge-transfer states Nature Photon., 2020, 10.1038/s41566-020-0668-z
 
4. Chihaya Adachi Nature, Kyushu University: Stable room temperature continuous wave lasing in a quasi-2D perovskite film
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Organic-inorganic lead halide quasi-two-dimensional (2D) perovskite has become a promising gain medium in laser applications due to its low cost, adjustable emission wavelength, excellent stability and solution processibility. Optically pumped continuous wave (CW) lasing is a high requirement for practical applications in high-density integrated optoelectronic devices, and is a key step towards electrically pumped lasers. However, due to the phenomenon of "laser death" (the laser is suddenly terminated under CW optical pumping), CW laser emission has not yet been achieved at room temperature, and the reason is not clear. Chihaya Adachi of Kyushu University has studied quasi-2D perovskite films with different organic cations based on lead halide, and observed that long-lived triplet excitons significantly hinder the doubling of spontaneous emission and optical pump pulses and CW lasers. Reverse. This result indicates that singlet-triplet exciton annihilation is a possible internal mechanism that causes laser death. By using a distributed feedback cavity with a high quality factor and applying a triplet management strategy, a stable quasi-2D perovskite green quasi-laser can be obtained under continuous light pumping in the air at room temperature. This discovery will pave the way for future current injection perovskite lasers. Literature link: Stable room-temperature continuous-wave lasing in quasi-2D perovskite films Nature, 2020, 10.1038/s41586-020-2621-1
 
5. Chihaya Adachi Nat. Commun., Kyushu University: Nanosecond-level time-delayed fluorescent molecules, suitable for dark blue OLEDs, with low efficiency degradation

 
The aromatic organic dark blue emitter exhibiting thermally activated delayed fluorescence (TADF) can collect all excitons in the electrically excited singlet and triplet states as light emission. However, the blue TADF emitter generally has a long exciton lifetime, resulting in a severe drop in efficiency due to exciton annihilation in an organic light emitting diode (OLED) at high current density and brightness. Chihaya Adachi of Kyushu University reported a dark blue TADF small molecule with a simple molecular design, in which the activation energy and the spin-orbit coupling between excited states with different spin multiplicity are simultaneously controlled. In the donor-acceptor molecular structure without heavy metals, the lifetime of excitons reaches 750 ns. The OLED using this TADF small molecule displays dark blue electroluminescence (EL), the CIE chromaticity coordinates are (0.14, 0.18), and the maximum EL quantum efficiency is 20.7%. In addition, even at high brightness, the highest maximum efficiency remains at 20.2% and 17.4%. Literature link: Nanosecond-time-scale delayed fluorescence molecule for deep-blue OLEDs with small efficiency rolloff Nat. Commun., 2020, 10.1038/s41467-020-15558-5
 
6. Chuanjiang Qin & Chihaya Adachi, Japan Science Promotion Agency: Triplet management can realize high-efficiency perovskite light-emitting diodes

 
Perovskite light-emitting diodes have high color purity and high performance, so they are expected to be used in next-generation lighting and displays. Although the management of singlet and triplet excitons is critical to the design of high-efficiency organic light-emitting diodes, the nature of how excitons affect performance in perovskite and quasi-two-dimensional (2D) perovskite-based devices remains unclear. . Chuanjiang Qin & Chihaya Adachi of Japan Science Promotion Agency showed that triplet excitons are the key to effective emission in green quasi-2D perovskite devices, and the quenching of triplet states by organic cations is the main loss path. The use of organic cations with high triplet energy levels in the quasi-2D perovskite based on FAPbBr3 can effectively harvest triplet states. The external quantum efficiency and current efficiency of this green (527 nm) device reached 12.4% and 52.1 cd/A, respectively. Literature link: Triplet management for efficient perovskite light-emitting diodes Nat. Photon., 2020, 10.1038/s41566-019-0545-9
 
7. Kyushu University Chihaya Adachi & Ryota Kabe Nat. Commun.: The effect of the energy gap between the charge transfer and the locally excited state on the organic long afterglow luminescence

 
Organic Persistent Luminescence (LPL) is an organic light-emitting system that slowly releases stored exciton energy as light. In terms of functionality, flexibility, transparency and solution processability, organic LPL materials have several advantages over inorganic LPL materials. However, the molecular selection strategy of organic LPL systems is still unclear. Chihaya Adachi & Ryota Kabe of Kyushu University found that the energy gap between the lowest local triplet excited state and the lowest singlet charge transfer excited state in the exciplex system significantly controls the LPL performance. For three donor materials with different energy gaps, the changes in LPL duration and spectral characteristics were systematically studied. When the energy level of the lowest triplet excited state is much lower than the energy level of the charge transfer excited state, the LPL duration of the system is short, and two different emission caused by exciplex fluorescence and donor phosphorescence are eliminated feature. Literature link: Influence of energy gap between charge-transfer and locally excited states on organic long persistence luminescence Nat. Commun., 2020, 10.1038/s41467-019-14035-y
 
8. Huang Wei & Lai Wenyong Nat. Commun.: Self-template synthesis of uniform hollow spheres based on highly conjugated three-dimensional covalent organic framework

 
Covalent organic framework (COF) has been used as a series of porous crystalline molecules for various promising applications. However, the controllable synthesis of COFs with uniform morphology is the most important, but still very challenging. Huang Wei & Lai Wenyong reported the self-template synthesis of uniform and unique hollow spheres based on highly conjugated three-dimensional (3D) COF. Studies have shown that nanoparticles with a maturation mechanism similar to Ostwald change from the initial nanospheres to a uniform hollow spherical structure. The generated 3D COF (3D-Sp-COF) is easy to transport ions more efficiently, and the lithium ion transfer number (t +) of 3D-Sp-COF reaches 0.7, even overwhelming most typical PEO-based polymer electrolytes. The hollow spherical structure shows enhanced capacitance performance, with a specific capacitance of 251 F/g at 0.5 A/g, which has advantages over most two-dimensional COF and other porous electrode materials. Literature link: Self-templated synthesis of uniform hollow spheres based on highly conjugated three-dimensional covalent organic frameworks Nat. Commun., 2020, 10.1038/s41467-020-18844-4
 
9. University of Macau Xing Guichuan & Huang Wei, Chen Yonghua Nat. Energy: Two-dimensional Ruddlesden–Pop layered perovskite solar cell based on pure phase film

 
The two-dimensional Ruddlesden-Pop layered metal halide perovskite has attracted more and more attention due to its ideal photoelectric performance and higher stability. However, such perovskites are usually composed of multiple quantum wells with random well width distribution. Xing Guichuan & Huang Wei and Chen Yonghua from the University of Macau reported a pure phase quantum well with a single well width by introducing a molten salt spacer n-butylamine acetate instead of the traditional halide spacer n-butylamine iodide. Due to the strong ion coordination between n-butylamine acetate and the perovskite framework, a uniformly distributed mesophase gel can be formed. This allows pure phase quantum well films with micron-sized vertically arranged crystal grains to crystallize from their respective mesophases. The power conversion efficiency of the obtained solar cell is 16.25%, and the high open circuit voltage is 1.31 V. After keeping it at 65±10% humidity for 4680 h, working at 85oC for 558 h or continuous lighting for 1100 h, the cell shows <10% The efficiency drops. Literature link: Two-dimensional Ruddlesden–Popper layered perovskite solar cells based on phase-pure thin films Nat. Energy, 2020, 10.1038/s41560-020-00721-5
 
10. Gao Feng of Linkoping University & Huang Wei and Wang Jianpu of Nanjing University of Technology Nat. Commun.: Mesophase-assisted low-temperature formation of γ-CsPbI3 thin films for high-efficiency deep red light-emitting devices

 
The black phase CsPbI3 is very attractive for optoelectronic devices, and the black phase CsPbI3 usually has a higher formation energy and requires an annealing temperature higher than 300°C. The formation energy can be significantly reduced by adding HI to the precursor. However, due to the high trap density and low photoluminescence quantum efficiency, the resulting film is not suitable for luminescence applications, and the formation mechanism at low temperature is not well understood. Gao Feng of Linkoping University & Huang Wei and Wang Jianpu of Nanjing University of Technology demonstrated a general method of γ-CsPbI3 film deposition with high photoluminescence quantum efficiency at 100°C by adding organic ammonium cations, and the resulting light-emitting diode showed 10.4 % External quantum efficiency and suppressed efficiency degradation. The article revealed that the low-temperature crystallization process is due to the formation of low-dimensional intermediate states, followed by ion exchange. This work provides a basis for adjusting the phase change pathway at low temperature in CsPbI3 device applications. Literature link: Intermediate-phase-assisted low-temperature formation of γ-CsPbI3 films for high-efficiency deep-red light-emitting devices Nat. Commun., 2020, 10.1038/s41467-020-18380-1
 
11. Huang Wei, Nanjing University of Posts and Telecommunications, and Nat. Commun. Xie Linghai: Stereo-selective and multi-grid formation of centrosymmetric molecular accumulation

 
Grid aromatics with well-defined edges and vertices represent general nanoscale building blocks for frame and architecture installation, but there are difficulties in stereoselective control during the synthesis process. Huang Wei and Xie Linghai from Nanjing University of Posts and Telecommunications reported on the diastereoselective gridding of a crescent-shaped superelectrophilic diazoferrocene substrate (AmBn), which is called Drawing Hands grids (DHGs) . During the gridding process of the A1B1 type substrate, the selectivity reached 75.6% of the diastereomeric excess, and during the polymerization process of the A2B2 type monomer, the mesoselectivity remained ~80%. This three-dimensional control stems from the centrosymmetric molecular stacking of two superelectrophiles with delocalized charges, which have coordinated π-π stacking attraction and Coulomb repulsion. Since the length of the regular three-dimensional structure is 20-30 nm, the Mark-Houwink index of the multigrid with alternating rigid loops/chains is 1.651, and the molecular weight (M) depends on the hydrodynamic radius Rh~M1.13. Through the simulation of chain collapse, the meso polyheteroarene still adopts a rod-like conformation, which is conducive to the high rigidity of organic nanopolymers, which is different from the cyclic skeleton of the rac-type polygrid. Literature link: Stereoselective gridization and polygridization with centrosymmetric molecular packing Nat. Commun., 2020, 10.1038/s41467-020-15401-x
 
12 Gao Feng of Linköping University, Sweden, Zhang Wenjing of Shenzhen University, and Huang Wei of Nanjing University of Technology Nat. Electron.: Two-way optical signal transmission between two identical devices using perovskite diodes

 
Integrating the generation and reception of optical signals into one device is of great significance in the development of miniaturized and integrated optoelectronic devices. However, conventional solution-processable semiconductors have inherent material and design limitations that prevent them from being used to manufacture devices with high performance. Gao Feng from Linköping University in Sweden, Wenjing Zhang from Shenzhen University, and Huang Wei from Nanjing University of Technology reported an efficient solution-processed perovskite diode that can work in both emission and detection modes. The device can switch between modes by changing the bias direction, and it exhibits light emission with an external quantum efficiency exceeding 21% and a sub-picowatt light detection limit. The operating speed of both functions can reach tens of megahertz. Thanks to the small Stokes shift of the perovskite, this diode has a high specific detection rate at its peak emission (~804 nm), allowing optical signal exchange between two identical diodes. To illustrate the potential of dual-function diodes, the author demonstrated that it can be used to create monolithic pulse sensors and bidirectional optical communication systems. Literature link: Bidirectional optical signal transmission between two identical devices using perovskite diodes Nat. Electron., 2020, 10.1038/s41928-020-0382-3
 
13 Zhang Lijun of Jilin University & Huang Wei of Nanjing University of Technology, Chen Yonghua Nat. Photon.: High-efficiency and stable Ruddlesden-Popper perovskite solar cell with customized interlayer molecular interaction

Two-dimensional Ruddlesden-Popper phase (2DRP) perovskite has better light stability and environmental stability than three-dimensional (3D). However, basic questions about the interaction between the bulky alkylammonium salt and the 2DRP perovskite framework still exist. Zhang Lijun of Jilin University & Huang Wei and Chen Yonghua of Nanjing University of Technology showed that the new bulk alkylammonium salt 2-(methylthio)ethylamine hydrochloride (MTEACl) has sulfur-sulfur interaction. In addition to the weak van der Waals interaction, the interaction between the sulfur atoms in the two MTEA molecules also makes the (MTEA)2(MA)4Pb5I16(n=5) perovskite framework have enhanced charge transport and stability. The result is that 2DRP perovskite solar cells have significantly improved efficiency and stability. The power conversion efficiency of the battery is as high as 18.06%, the humidity resistance is as high as 1512 h, and the thermal stability is 375 h. Literature link: Efficient and stable Ruddlesden–Popper perovskite solar cell with tailored interlayer molecular interaction Nat. Photon., 2020, 10.1038/s41566-019-0572-6
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