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1. ipso ‐Arylative Ring‐Opening Polymerization as a Route to Electron‐Deficient Conjugated Polymers

   https://doi.org/10.1002/anie.201809610  

   Shih, Feng‐Yang ; Choi, Deokkyu ; Wu, Qin ; Nam, Chang‐Yong ; Grubbs, Robert B. ( December 2018 , Angewandte Chemie International Edition)

   ipso‐Arylative ring‐opening polymerization of 2‐bromo‐8‐aryl‐8H‐indeno[2,1‐b]thiophen‐8‐ol monomers proceeds to M_nup to 9 kg mol⁻¹with conversion of the monomer diarylcarbinol groups to pendent conjugated aroylphenyl side chains (2‐benzoylphenyl or 2‐(4‐hexylbenzoyl)phenyl), which influence the optical and electronic properties of the resulting polythiophenes. Poly(3‐(2‐(4‐hexylbenzoyl)phenyl)thiophene) was found to have lower frontier orbital energy levels (HOMO/LUMO=−5.9/−4.0 eV) than poly(3‐hexylthiophene) owing to the electron‐withdrawing ability of the aryl ketone side chains. The electron mobility (ca. 2×10⁻³ cm² V⁻¹ s⁻¹) for poly(3‐(2‐(4‐hexylbenzoyl)phenyl)thiophene) was found to be significantly higher than the hole mobility (ca. 8×10⁻⁶ cm² V⁻¹ s⁻¹), which suggests such polymers are candidates for n‐type organic semiconductors. Density functional theory calculations suggest that backbone distortion resulting from side‐chain steric interactions could be a key factor influencing charge mobilities.

    

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2. Wafer-Scale Synthesis of WS 2 Films with In Situ Controllable p-Type Doping by Atomic Layer Deposition

   https://doi.org/10.34133/2021/9862483  

   Yang, Hanjie ; Wang, Yang ; Zou, Xingli ; Bai, Rongxu ; Wu, Zecheng ; Han, Sheng ; Chen, Tao ; Hu, Shen ; Zhu, Hao ; Chen, Lin ; et al ( January 2021 , Research)

   Wafer-scale synthesis of p-type TMD films is critical for its commercialization in next-generation electro/optoelectronics. In this work, wafer-scale intrinsic n-type WS₂films and in situ Nb-doped p-type WS₂films were synthesized through atomic layer deposition (ALD) on 8-inchα-Al₂O₃/Si wafers, 2-inch sapphire, and 1 cm²GaN substrate pieces. The Nb doping concentration was precisely controlled by altering cycle number of Nb precursor and activated by postannealing. WS₂n-FETs and Nb-doped p-FETs with different Nb concentrations have been fabricated using CMOS-compatible processes. X-ray photoelectron spectroscopy, Raman spectroscopy, and Hall measurements confirmed the effective substitutional doping with Nb. The on/off ratio and electron mobility of WS₂n-FET are as high as 10⁵and 6.85 cm² V^-1 s^-1, respectively. In WS₂p-FET with 15-cycle Nb doping, the on/off ratio and hole mobility are 10 and 0.016 cm² V^-1 s^-1, respectively. The p-n structure based on n- and p- type WS₂films was proved with a 10⁴rectifying ratio. The realization of controllablein situNb-doped WS₂films paved a way for fabricating wafer-scale complementary WS₂FETs.

    

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3. Probing Charge Transport and Background Doping in Metal‐Organic Chemical Vapor Deposition‐Grown (010) β‐Ga 2 O 3

   https://doi.org/10.1002/pssr.202000145  

   Feng, Zixuan ; Bhuiyan, A. F. M. Anhar Uddin ; Xia, Zhanbo ; Moore, Wyatt ; Chen, Zhaoying ; McGlone, Joe F. ; Daughton, David R. ; Arehart, Aaron R. ; Ringel, Steven A. ; Rajan, Siddharth ; et al ( June 2020 , physica status solidi (RRL) – Rapid Research Letters)

   A new record‐high room‐temperature electron Hall mobility (μ_RT = 194 cm² V⁻¹ s⁻¹atn ≈ 8 × 10¹⁵ cm⁻³) for β‐Ga₂O₃is demonstrated in the unintentionally doped thin film grown on (010) semi‐insulating substrate via metal‐organic chemical vapor deposition (MOCVD). A peak electron mobility of ≈9500 cm² V⁻¹ s⁻¹is achieved at 45 K. Further investigation on the transport properties indicates the existence of sheet charges near the epilayer/substrate interface. Si is identified as the primary contributor to the background carrier in both the epilayer and the interface, originating from both surface contamination and growth environment. The pregrowth hydrofluoric acid cleaning of the substrate leads to an obvious decrease in Si impurity both at the interface and in the epilayer. In addition, the effect of the MOCVD growth condition, particularly the chamber pressure, on the Si impurity incorporation is studied. A positive correlation between the background charge concentration and the MOCVD growth pressure is confirmed. It is noteworthy that in a β‐Ga₂O₃film with very low bulk charge concentration, even a reduced sheet charge density plays an important role in the charge transport properties.

    

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4. Enhanced Piezoelectric, Ferroelectric, and Electrostrictive Properties of Lead‐Free (1‐ x )BCZT‐( x )BCST Electroceramics with Energy Harvesting Capability

   https://doi.org/10.1002/smll.202300549  

   Baraskar, Bharat G. ; Kolekar, Yesappa D. ; Thombare, Balu. R. ; James, Ajit. R. ; Kambale, Rahul C. ; Ramana, C. V. ( May 2023 , Small)

   Next‐generation electronics and energy technologies can now be developed as a result of the design, discovery, and development of novel, environmental friendly lead (Pb)‐free ferroelectric materials with improved characteristics and performance. However, there have only been a few reports of such complex materials’ design with multi‐phase interfacial chemistry, which can facilitate enhanced properties and performance. In this context, herein, novel lead‐free piezoelectric materials (1‐x)Ba_0.95Ca_0.05Ti_0.95Zr_0.05O₃‐(x)Ba_0.95Ca_0.05Ti_0.95Sn_0.05O₃, are reported, which are represented as (1‐x)BCZT‐(x)BCST, with demonstrated excellent properties and energy harvesting performance. The (1‐x)BCZT‐(x)BCST materials are synthesized by high‐temperature solid‐state ceramic reaction method by varyingxin the full range (x= 0.00–1.00). In‐depth exploration research is performed on the structural, dielectric, ferroelectric, and electro‐mechanical properties of (1‐x)BCZT‐(x)BCST ceramics. The formation of perovskite structure for all ceramics without the presence of any impurity phases is confirmed by X‐ray diffraction (XRD) analyses, which also reveals that the Ca²⁺, Zr⁴⁺, and Sn⁴⁺are well dispersed within the BaTiO₃lattice. For all (1‐x)BCZT‐(x)BCST ceramics, thorough investigation of phase formation and phase‐stability using XRD, Rietveld refinement, Raman spectroscopy, high‐resolution transmission electron microscopy (HRTEM), and temperature‐dependent dielectric measurements provide conclusive evidence for the coexistence of orthorhombic + tetragonal (Amm2+P4mm) phases at room temperature. The steady transition ofAmm2crystal symmetry toP4mmcrystal symmetry with increasingxcontent is also demonstrated by Rietveld refinement data and related analyses. The phase transition temperatures, rhombohedral‐orthorhombic (T_R‐O), orthorhombic‐ tetragonal (T_O‐T), and tetragonal‐cubic (T_C), gradually shift toward lower temperature with increasingxcontent. For (1‐x)BCZT‐(x)BCST ceramics, significantly improved dielectric and ferroelectric properties are observed, including relatively high dielectric constantε_r≈ 1900–3300 (near room temperature),ε_r≈ 8800–12 900 (near Curie temperature), dielectric loss, tanδ≈ 0.01–0.02, remanent polarizationP_r≈ 9.4–14 µC cm⁻², coercive electric fieldE_c≈ 2.5–3.6 kV cm⁻¹. Further, high electric field‐induced strainS≈ 0.12–0.175%, piezoelectric charge coefficientd₃₃≈ 296–360 pC N⁻¹, converse piezoelectric coefficient ≈ 240–340 pm V⁻¹, planar electromechanical coupling coefficientk_p≈ 0.34–0.45, and electrostrictive coefficient (Q₃₃)_avg≈ 0.026–0.038 m⁴C⁻²are attained. Output performance with respect to mechanical energy demonstrates that the (0.6)BCZT‐(0.4)BCST composition (x= 0.4) displays better efficiency for generating electrical energy and, thus, the synthesized lead‐free piezoelectric (1‐x)BCZT‐(x)BCST samples are suitable for energy harvesting applications. The results and analyses point to the outcome that the (1‐x)BCZT‐(x)BCST ceramics as a potentially strong contender within the family of Pb‐free piezoelectric materials for future electronics and energy harvesting device technologies.

    

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5. 3,4,5‐Trimethoxy Substitution on an N‐DMBI Dopant with New N‐Type Polymers: Polymer‐Dopant Matching for Improved Conductivity‐Seebeck Coefficient Relationship

   https://doi.org/10.1002/anie.202110505  

   Han, Jinfeng ; Chiu, Arlene ; Ganley, Connor ; McGuiggan, Patty ; Thon, Susanna M. ; Clancy, Paulette ; Katz, Howard E. ( November 2021 , Angewandte Chemie International Edition)

   Achieving high electrical conductivity and thermoelectric power factor simultaneously for n‐type organic thermoelectrics is still challenging. By constructing two new acceptor‐acceptor n‐type conjugated polymers with different backbones and introducing the 3,4,5‐trimethoxyphenyl group to form the new n‐type dopant 1,3‐dimethyl‐2‐(3,4,5‐trimethoxyphenyl)‐2,3‐dihydro‐1H‐benzo[d]imidazole (TP‐DMBI), high electrical conductivity of 11 S cm⁻¹and power factor of 32 μW m⁻¹ K⁻²are achieved. Calculations using Density Functional Theory show that TP‐DMBI presents a higher singly occupied molecular orbital (SOMO) energy level of −1.94 eV than that of the common dopant 4‐(1, 3‐dimethyl‐2, 3‐dihydro‐1H‐benzoimidazol‐2‐yl) phenyl) dimethylamine (N‐DMBI) (−2.36 eV), which can result in a larger offset between the SOMO of dopant and lowest unoccupied molecular orbital (LUMO) of n‐type polymers, though that effect may not be dominant in the present work. The doped polymer films exhibit higher Seebeck coefficient and power factor than films using N‐DMBI at the same doping levels or similar electrical conductivity levels. Moreover, TP‐DMBI doped polymer films offer much higher electron mobility of up to 0.53 cm² V⁻¹ s⁻¹than films with N‐DMBI doping, demonstrating the potential of TP‐DMBI, and 3,4,5‐trialkoxy DMBIs more broadly, for high performance n‐type organic thermoelectrics.

    

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