An Amorphous n-Type Conjugated Polymer with an Ultra-Rigid Planar Backbone

High charge carrier mobility polymer semiconductors are always semi-crystalline. Amorphous conjugated polymers represent another kind of polymer semiconductors with different charge transporting mechanism. Here we report the first near-amorphous n-type conjugated polymer with decent electron mobility, which features a remarkably rigid, straight and planar polymer backbone. The molecular design strategy is to copolymerize two fused-ring building blocks which are both electron-accepting, centrosymmetrical and planar. The polymer is the alternating copolymer of double B←N bridged bipyridine (BNBP) unit and benzobisthiazole (BBTz) unit. It shows a decent electron mobility of 0.34 cm² V⁻¹ s⁻¹ in organic field-effect transistors. The excellent electron transporting property of the polymer is possibly due to the ultrahigh backbone stiffness, small π-π stacking distance, and high molecular weight.     

Functionalized Phenanthrene Imide-Based Polymers for n-Type Organic Thin-Film Transistors

High-performing n-type polymers are crucial for the advance of organic electronics field, however strong electron-deficient building blocks with optimized physicochemical properties for constructing them are still limited. The imide-functionalized polycyclic aromatic hydrocarbons ( PAH s) with extended π-conjugated framework, high electron deficiency and good solubility serve as promising candidates for developing high-performance n-type polymers. Among the PAH s, phenanthrene ( PhA ) features a well-delocalized aromatic π-system with multiple modifiable active sites . However, the PhA -based imides are seldom studied, mainly attributed to the synthetic challenge. Herein, we report two functionalized PhA s, CPOI and CPCNI , by simultaneously incorporating imide with carbonyl or dicyanomethylene onto PhA . Notably, the dicyanomethylene-modified CPCNI exhibits a well stabilized LUMO energy level (−3.84 eV), attributed to the synergetic inductive effect from imide and cyano groups. Subsequently, based on CPOI and CPCNI , two polymers PCPOI-Tz and PCPCNI-Tz were developed. Applied to organic thin-film transistors, owing to the strong electron-deficiency of CPCNI , polymer PCPCNI-Tz shows an improved electron mobility and largely decreased threshold voltage compared with PCPOI-Tz . This work affords two structurally novel electron-deficient building blocks and highlights the effectiveness of dual functionalization of PhA s with strong electron-withdrawing groups for devising n-type polymers.     

Electrochemical Characterization of Chemically Synthesized Polythiophene Thin Films: Performance of Asymmetric Supercapacitor Device

Polythiophene (PT) thin films have been prepared by chemical bath deposition (CBD) method at room temperature (300 K) via oxidative polymerization of thiophene using ammonium peroxodisulfate (APS) as an oxidizing agent. Globular particulates of PT are deposited on the stainless steel and glass substrates. The morphology and chain structure of PT are studied using scanning electron microscopy (SEM) and Raman spectroscopy techniques, respectively. The electrochemical behavior of PT electrode is studied using cyclic voltammetry and galvanostatic charge? discharge studies. PT thin film shows maximum specific capacitance of 300 F g^?1 at 5 mV s^?1 in 0.1 M LiClO₄/PC electrolyte. The asymmetric device formed with PT and graphite shows supercapacitive properties useful in the power applications.     

Self-Doped n-Type Quinoidal Compounds with Good Air Stability and High Electrical Conductivity for Organic Electronics

Air stable n-type conductive molecules with high electrical conductivities and excellent device performance have important applications in organic electronics, but their synthesis remains challenging. Herein, we report three self-doped n-type conductive molecules, designated QnNs, with a closed-shell quinoidal backbone and alkyl amino chains of different lengths. The QnNs are self-doped by intermolecular electron transfer from the amino groups to the quinoidal backbone. This process is ascertained unambiguously by experiments and theoretical calculations. The use of a quinoidal structure effectively improves the self-doping level, and thus increases the electrical conductivity of self-doped n-type conductive molecules achieved by a closed-shell structure from<10⁻⁴ S cm⁻¹ to>0.03 S cm⁻¹. Furthermore, the closed-shell quinoidal structure results in good air stability of the QnNs, with half-lives>73 days; and Q4N shows an electrical conductivity of 0.019 S cm⁻¹ even after exposure to air for 120 days. When applying Q6N as the cathode interlayer in organic solar cells (OSCs), an outstanding power conversion efficiency of up to 18.2 % was obtained, which represents one the best results in binary OSCs.     

导电高分子及其纳米复合材料的热电性质

与无机热电材料相比, 有机热电材料具有资源丰富、 成本低、 质量轻、 柔韧性好及热导率低等优点, 成为热电研究领域关注的热点. 理论和实验结果表明, 低维化和小尺度化是热电材料研究和开发的发展方向. 本文对低维有机热电材料的合成、 器件组装及热电性质的影响因素等进行简要评述, 并对低维有机热电材料的研究方向进行了讨论.     

Non-Covalent Interactions between Polyvinyl Chloride and Conjugated Polymers Enable Excellent Mechanical Properties and High Stability in Organic Solar Cells

The incorporation of insulating polymers into conjugated polymers has been widely explored as a strategy to improve mechanical properties of flexible organic electronics. However, phase separation due to the immiscibility of these polymers has limited their effectiveness. In this study, we report the discovery of multiple non-covalent interactions that enhances the miscibility between insulating and conjugated polymers, resulting in improved mechanical properties. Specifically, we have added polyvinyl chloride (PVC) into the conjugated polymer PM6 and observed a significant increase in solution viscosity, indicative of favorable miscibility between these two polymers. This phenomenon has been rarely observed in other insulating/conjugated polymer composites. Thin films of PM6/PVC exhibit a much-improved crack-onset strain of 19.35 %, compared to 10.12 % for pristine PM6 films. Analysis reveal that a “cyclohexyl-like” structure formed through dipole-dipole interactions and hydrogen bonding between PVC and PM6 acted as a cross-linking site in the thin films, leading to improved mechanical properties. Moreover, PM6/PVC blend films have demonstrated excellent thermal and bending stability when applied as an electron donor in organic solar cells. These findings provide new insights into non-covalent interactions that can be utilized to enhance the properties of conjugated polymers and may have potential applications in flexible organic electronics.     

N-Doped Nonalternant Nanoribbons with Excellent Nonlinear Optical Performance

Two novel N-doped nonalternant nanoribbons ( NNNR-1 and NNNR-2 ) featuring multiple fused N-heterocycles and bulky solubilizing groups were prepared via bottom-up solution synthesis. NNNR-2 achieves a total molecular length of 33.8 Å, which represents the longest soluble N-doped nonalternant nanoribbon reported to date. The pentagon subunits and doping of N atoms in NNNR-1 and NNNR-2 have successfully regulated their electronic properties, achieving high electron affinity and good chemical stability enabled by the nonalternant conjugation and electronic effects. When applied a laser pulse of 532 nm, the 13-rings nanoribbon NNNR-2 shows outstanding nonlinear optical (NLO) responses, with the nonlinear extinction coefficient of 374 cm GW⁻¹, much higher than those of NNNR-1 (96 cm GW⁻¹) and the well-known NLO material C₆₀ (153 cm GW⁻¹). Our findings indicate that the N-doping of nonalternant nanoribbons is an effective strategy to access another type of excellent material system for high-performance NLO applications, which can be extended to construct numerous heteroatom-doped nonalternant nanoribbons with fine-tunable electronic properties.     

侧链含自由基单元的1,4-吡咯并吡咯二酮共轭聚合物的合成和半导体性质研究

合成了两个侧链含有2,2,6,6-四甲基哌啶-1-氧自由基单元(TEMPO)的1,4-吡咯并吡咯二酮(DPP)共轭聚合物PDPP4T-1和PDPP4T-2,并开展了其半导体性质研究。薄膜场效应晶体管器件测试结果显示,相对于不含TEMPO的聚合物PDPP4T,PDPP4T-1和PDPP4T-2的场效应器件性能有所降低,不过,含TEMPO的聚合物器件性能最高仍达到了2.12cm²·V^-1·s^-1。进一步通过原子力显微镜和X射线衍射对TEMPO引入后导致性能降低的可能原因进行了研究。     

NaCdSb: An Orthorhombic Zintl Phase with Exceptional Intrinsic Thermoelectric Performance

Many Zintl phases are promising thermoelectric materials owning to their features like narrow band gaps, multiband behaviors, ideal charge transport tunnels, and loosely bound cations. Herein we show a new Zintl phase NaCdSb with exceptional intrinsic thermoelectric performance. Pristine NaCdSb exhibits semiconductor behaviors with an experimental hole concentration of 2.9×10¹⁸ cm⁻³ and a calculated band gap of 0.5 eV. As the temperature increases, the hole concentration rises gradually and approaches its optimal one, leading to a high power factor of 11.56 μW cm⁻¹ K⁻² at 673 K. The ultralow thermal conductivity is derived from the small phonon group velocity and short phonon lifetime, ascribed to the structural anharmonicity of Cd−Sb bonds. As a consequence, a maximum zT of 1.3 at 673 K has been achieved without any doping optimization or structural modification, demonstrating that NaCdSb is a remarkable thermoelectric compound with great potential for performance improvement.     

Pyrazine-linked Iron-coordinated Tetrapyrrole Conjugated Organic Polymer Catalyst with Spatially Proximate Donor-Acceptor Pairs for Oxygen Reduction in Fuel Cells

Nitrogen-coordinated iron (Fe−N₄) materials represent the most promising non-noble electrocatalysts for the cathodic oxygen reduction reaction (ORR) of fuel cells. However, molecular-level structure design of Fe−N₄ electrocatalyst remains a great challenge. In this study, we develop a novel Fe−N₄ conjugated organic polymer (COP) electrocatalyst, which allows for precise design of the Fe−N₄ structure, leading to unprecedented ORR performance. At the molecular level, we have successfully organized spatially proximate iron-pyrrole/pyrazine (FePr/Pz) pairs into fully conjugated polymer networks, which in turn endows FePr sites with firmly covalent-bonded matrix, strong d-π electron coupling and highly dense distribution. The resulting pyrazine-linked iron-coordinated tetrapyrrole (Pz−FeTPr) COP electrocatalyst exhibits superior performance compared to most ORR electrocatalysts, with a half-wave potential of 0.933 V and negligible activity decay after 40,000 cycles. When used as the cathode electrocatalyst in a hydroxide exchange membrane fuel cell, the Pz−FeTPr COP achieves a peak power density of ≈210 mW cm⁻². We anticipate the COP based Fe−N₄ catalyst design could be an effective strategy to develop high-performance catalyst for facilitating the progress of fuel cells.     

Mg(C3O4H2)(H2O)2: A New Ultraviolet Nonlinear Optical Material Derived from KBe2BO3F2 with High Performance and Excellent Water-Resistance

Acquiring high-performance ultraviolet (UV) nonlinear optical (NLO) materials that simultaneously exhibit a strong second harmonic generation (SHG) coefficients, as short as possible SHG phase-matching (PM) wavelength and non-hygroscopic properties has consistently posed a significant challenge. Herein, through multicomponent modification of KBe₂BO₃F₂ (KBBF), an excellent UV NLO crystal, Mg(C₃O₄H₂)(H₂O)₂, was successfully synthesized in malonic system. This material possesses a unique 2D NLO-favorable electroneutral [Mg(C₃O₄H₂)₃(H₂O)₂]_∞ layer, resulting in the rare coexistence of a strong SHG response of 3×KDP (@1064 nm) and short PM wavelength of 200 nm. More importantly, it exhibits exceptional water resistance, which is rare among ionic organic NLO crystals. Theoretical calculations revealed that its excellent water-resistant may be originated from its small available cavity volumes, which is similar to the famous LiB₃O₅ (LBO). Therefore, excellent NLO properties and stability against air and moisture indicate it should be a promising UV NLO crystal.