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1. Preserving the shape of silver nanocubes under corrosive environment by covering their edges and corners with iridium

   https://doi.org/10.1039/d0nr05969b  

   Wang, Peng ; Ahn, Jaewan ; Gao, Ruoqi ; Qin, Dong ( October 2020 , Nanoscale)

   null (Ed.)

   Silver nanocubes have found use in an array of applications but their performance has been plagued by the shape instability arising from the oxidation and dissolution of Ag atoms from the edges and corners. Here we demonstrate that the shape of Ag nanocubes can be well preserved by covering their edges and corners with a corrosion-resistant metal such as Ir. In a typical process, we titrate a Na 3 IrCl 6 solution in ethylene glycol (EG) into a suspension of Ag nanocubes in an EG solution in the presence of poly(vinylpyrrolidone) (PVP) held at 110 °C. The Ir atoms derived from the reduction of Na 3 IrCl 6 by EG and Ag are deposited onto the edges and then corners for the generation of Ag–Ir core-frame nanocubes. Remarkably, our results indicate that a small amount of Ir atoms on the edges and corners is adequate to prevent the Ag nanocubes from transforming into nanospheres when heated in a PVP/EG solution up to 110 °C. We further demonstrate that these Ag–Ir nanocubes embrace plasmonic properties comparable to those of the original Ag nanocubes, making them immediately useful in a variety of applications. This strategy for stabilizing the shape of Ag nanocubes should be extendible to Ag nanocrystals with other shapes or nanocrystals comprised of other metals. 

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2. n‐Doping of a Low‐Electron‐Affinity Polymer Used as an Electron‐Transport Layer in Organic Light‐Emitting Diodes

   https://doi.org/10.1002/adfm.202000328  

   Smith, Hannah L. ; Dull, Jordan T. ; Longhi, Elena ; Barlow, Stephen ; Rand, Barry P. ; Marder, Seth R. ; Kahn, Antoine ( February 2020 , Advanced Functional Materials)

   n‐Doping electron‐transport layers (ETLs) increases their conductivity and improves electron injection into organic light‐emitting diodes (OLEDs). Because of the low electron affinity and large bandgaps of ETLs used in green and blue OLEDs, n‐doping has been notoriously more difficult for these materials. In this work, n‐doping of the polymer poly[(9,9‐dioctylfluorene‐2,7‐diyl)‐alt‐(benzo[2,1,3]thiadiazol‐4,7‐diyl)] (F8BT) is demonstrated via solution processing, using the air‐stable n‐dopant (pentamethylcyclopentadienyl)(1,3,5‐trimethylbenzene)ruthenium dimer [RuCp*Mes]₂. Undoped and doped F8BT films are characterized using ultraviolet and inverse photoelectron spectroscopy. The ionization energy and electron affinity of the undoped F8BT are found to be 5.8 and 2.8 eV, respectively. Upon doping F8BT with [RuCp*Mes]₂, the Fermi level shifts to within 0.25 eV of the F8BT lowest unoccupied molecular orbital, which is indicative of n‐doping. Conductivity measurements reveal a four orders of magnitude increase in the conductivity upon doping and irradiation with ultraviolet light. The [RuCp*Mes]₂‐doped F8BT films are incorporated as an ETL into phosphorescent green OLEDs, and the luminance is improved by three orders of magnitude when compared to identical devices with an undoped F8BT ETL.

    

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3. Batch‐Sprayed and Stamp‐Transferred Electrodes: A New Paradigm for Scalable Fabrication of Multilayer Dielectric Elastomer Actuators

   https://doi.org/10.1002/adfm.202205394  

   Cohen, Andy J. ; Kollosche, Matthias ; Yuen, Michelle C. ; Lee, Dae‐Young ; Clarke, David R. ; Wood, Robert J. ( August 2022 , Advanced Functional Materials)

   Multilayer dielectric elastomer actuators  have a wide range of potential applications, but their development and commercial implementation have been hindered by existing manufacturing processes. Existing processes are low‐throughput, limited in area, and/or can only process a narrow range of elastomers. This study presents a novel fabrication paradigm that overcomes these challenges: instead of sequentially patterning electrodes directly onto successive elastomer layers, electrode stamps are patterned onto a carrier film in an independent batch‐spray process and the electrodes are then stamp‐transferred onto each elastomer layer. By modularizing the production and assembly of electrodes, a laboratory‐scale implementation of the process achieves a throughput of 15 layers h⁻¹, a maximum electrode size of 300×300 mm, and tuning‐free compatibility with a wide range of elastomers. The batch‐spraying paradigm also provides the unique capability to evaluate and modify electrodes before they are assembled into a multilayer; a method of mechanically treating the electrodes is employed to increase the breakdown strength of Elastosil P7670 devices from 15.7 to 33.5 V µm⁻¹. The electrodes are conductive up to a strain of more than 200% and add negligible stiffness to the multilayer structure. The capabilities of this process to produce useful devices are demonstrated with a large‐area loudspeaker and an actuator with 60 active layers.

    

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4. A Solution Processable High‐Performance Thermoelectric Copper Selenide Thin Film

   https://doi.org/10.1002/adma.201606662  

   Lin, Zhaoyang ; Hollar, Courtney ; Kang, Joon Sang ; Yin, Anxiang ; Wang, Yiliu ; Shiu, Hui‐Ying ; Huang, Yu ; Hu, Yongjie ; Zhang, Yanliang ; Duan, Xiangfeng ( March 2017 , Advanced Materials)

   A solid‐state thermoelectric device is attractive for diverse technological areas such as cooling, power generation and waste heat recovery with unique advantages of quiet operation, zero hazardous emissions, and long lifetime. With the rapid growth of flexible electronics and miniature sensors, the low‐cost flexible thermoelectric energy harvester is highly desired as a potential power supply. Herein, a flexible thermoelectric copper selenide (Cu₂Se) thin film, consisting of earth‐abundant elements, is reported. The thin film is fabricated by a low‐cost and scalable spin coating process using ink solution with a truly soluble precursor. The Cu₂Se thin film exhibits a power factor of 0.62 mW/(m K²) at 684 K on rigid Al₂O₃substrate and 0.46 mW/(m K²) at 664 K on flexible polyimide substrate, which is much higher than the values obtained from other solution processed Cu₂Se thin films (<0.1 mW/(m K²)) and among the highest values reported in all flexible thermoelectric films to date (≈0.5 mW/(m K²)). Additionally, the fabricated thin film shows great promise to be integrated with the flexible electronic devices, with negligible performance change after 1000 bending cycles. Together, the study demonstrates a low‐cost and scalable pathway to high‐performance flexible thin film thermoelectric devices from relatively earth‐abundant elements.

    

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5. 3D Conformal Printing and Photonic Sintering of High‐Performance Flexible Thermoelectric Films Using 2D Nanoplates

   https://doi.org/10.1002/adfm.201901930  

   Saeidi‐Javash, Mortaza ; Kuang, Wenzheng ; Dun, Chaochao ; Zhang, Yanliang ( July 2019 , Advanced Functional Materials)

   Flexible thermoelectric (TE) devices hold great promise for energy harvesting and cooling applications, with increasing significance to serve as perpetual power sources for flexible electronics and wearable devices. Despite unique and superior TE properties widely reported in nanocrystals, transforming these nanocrystals into flexible and functional forms remains a major challenge. Herein, demonstrated is a transformative 3D conformal aerosol jet printing and rapid photonic sintering process to print and sinter solution‐processed Bi₂Te_2.7Se_0.3nanoplate inks onto virtually any flexible substrates. Within seconds of photonic sintering, the electrical conductivity of the printed film is dramatically improved from nonconductive to 2.7 × 10⁴S m⁻¹. The films demonstrate a room temperature power factor of 730 µW m⁻¹K⁻², which is among the highest values reported in flexible TE films. Additionally, the film shows negligible performance changes after 500 bending cycles. The highly scalable and low‐cost fabrication process paves the way for large‐scale manufacturing of flexible devices using a variety of high‐performing nanoparticle inks.

    

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