Weilaizhixing, the highest ever undoped conductive polymer
Multipurpose conductor emerging technical requirements simultaneously have mechanical properties, geometry and Engineering (opto) electronic functions, which is the conventional materials can not match. Wherein the conductive polymer (CPs) has the absolute advantage, such as the possibility to adjust the molecular and electronic structure by chemical synthesis, and the low-temperature method for manufacturing a large area and adapted to various forms of factors. Typically CPs, such as poly (3,4 – ethylene dioxythiophene) required to achieve high electrical conductivity ([sigma]) by doping, implementation of mobile charge carriers in the form of polarons and bipolarons. Although researchers worldwide efforts to get satisfactory σ value, but doping also brought a series of adverse consequences, such as high variability instability of chemical reactivity, materials and equipment, processing and performance, and with various substrates and electronic components incompatibility. At the same time, the need to overcome the organic material in the chemical doping system, there are still many significant challenges. Many previous studies have shown that open-shell polymer DA has a strong π- correlation can promote the formation of a variety of electronic states, providing new opportunities for the development of conductive material. Therefore, there remains an urgent need for bottom-up chemical binding band gap structure and electronic control, the conformational details, aspects and associated transport phenomena associated with the emerging systems which may provide. Based on this, recently, Jason D. Azoulay et University of Southern Mississippi US researchers demonstrated using cyclopentadienyl-thiadiazole and thiophene-quinoline open shell composed of alternating conjugated polymer can be obtained at a high undoped native form conductivity. Spectroscopy, electrochemical, electron paramagnetic resonance and magnetic susceptibility measurements show that the donor – acceptor framework to promote the formation of a very narrow band gap, strong electron correlation, high spin ground state and a long range delocalized π-. Comparative studies of the structure and processing method showed variable conductivity adjusted to 8.18 S cm-1, a narrow band gap than the other neutral conjugated polymer, doped with many polymers, radical conductor, and with poly ( styrene – sulfonate) – doped poly (3,4-dioxythiophene) comparable to commercial grade material. X-ray and morphological studies have shown that by the interaction of high conductivity and strong π formed by self-organization of the long-range order to produce a rigid backbone conformation, resulting in open shell site delocalized electronic communications network. The research results, entitled \”Open-Shell Donor-Acceptor Conjugated Polymers with High Electrical Conductivity \”papers published in the\” Advanced Functional Materials \”(see the text description link)
Preparation of static cross-coupled open-shell-type donor Method – acceptor conjugated polymer [123 DA open shell polymer backbone thiadiazol-quinoline (CPDT-TQ), as shown in configuration 1 .CPDT donor improved the highest occupied molecular orbital (HOMO) -] thiophene series having a cyclopentadiene researchers prepared and promotes a rigid backbone, the side chains provides a linearly -C16H33 solubility strong front receptors TQ reduced quinones lowest unoccupied molecular orbital (the LUMO), promotes strong intramolecular interaction, promote a very narrow band gap, a pattern bonded quinones, rigid backbone and unpaired spin density with methyl (Pl), phenyl (P2) and thiophene (P3) substituted TQ receptor, and polymer structure can be fine-tune the electronic properties
solid state properties [123 ] Figure 1a shows the absorption spectrum of polymer films maximum (max) followed by 1.60 μm (P1), 1.45 μm (P2), 1.66 μm (P3) and a relatively sharp band tail undoped polymer characterized in voltammetry display method, P1 is located in the HOMO of -4.93 eV, LUMO located -3.90 eV, so electrochemical bandgap (Egelec) is 1.03 eV (FIG. 1b). compared with the P1, P2 and P3 accumulation amount significantly reduced (Figure 1a) .P2 electrochemical characteristics and P3 (P2: EHOMO = -5.06 eV, ELUMO = -4.19 eV, = 0.87 eV; P3: EHOMO = -4.95 eV, ELUMO = -4.15 eV, = 0.80 eV), also described substituent group frontier orbital energy may be varied (FIG. 1b). electron paramagnetic resonance (EPR) spectrum at room temperature in g- factor (g) of 2.006, followed by a spin concentration 6.03 × 1022 (P1), 6.68 × 1022 (P2) and 5.23 × 1022 spins mDisplay ol-1 (P3) a broad singlet, and spectral properties similar to a dipole (FIG. 1c). P1 EPR with increasing temperature of the cooling intensity, exhibit paramagnetic ground state (FIG. 1e). Measuring the superconducting quantum interference device (SQUID-) magnetic method in which an anti-magnetic state, which is also shown as the temperature changes, such as when the temperature is increased 2 from 50 K, the magnetic susceptibility ([chi]) sharp decline; and when the temperature changes in the range of 50-300 K, magnetic susceptibility ([chi]) is maintained relatively flat (FIG. 1f). Two-point probe measurement shows a linear current-voltage P1-P3 of (I-V) characteristics were σRT = 3.05 × 10-2, 9.25 × 10-5 and 4.13 × 10-4 S cm-1 (FIG. 1 d).
spin coating grazing incidence angle X-ray scattering (GIWAXS) show cross-section, a weak crystal Pl, and P2 and P3 are almost amorphous (FIG. 2a, b). Three polymers are present peak low q (≈0.25 Å-1, 25.13 Å) and no higher-order Bragg reflection, this is due to a weakly-ordered layered accumulation caused from the polymer side chain (100) scattered peak can be seen. (AFM) can be seen from FIG atomic force microscope, P1 spin-coated film exhibits self-assembled nanostructures 100 nm diameter semicircular RMS (RMS) roughness of 1.62 nm, the polymer built up of interconnected grid results in a higher σRT (FIG. 2c). In contrast, P2 and P3 film surface relatively smooth (RMS roughness was 0.40 nm, respectively, and 0.32 nm), aggregates of small particles randomly distributed on the surface of a particle size of 510nm. At room temperature, fast spin-lattice relaxation dominates, followed like Eliot – Yafei Te mechanism. Thus, when the emergence of more effective ways, and may interact shock wave function along the backbone of the more robust or enhanced π-π, will reduce the spin relaxation time (FIG. 2a, b).
for PA film, when dried slowly CHCl3, σRT enhanced nearly 100 times the average value increased from 3.05 × 10-2 2.46 S cm-1, and high-performance devices made over 8 S cm-1, and when the film P1 when placed in hexanes slowly dried, σRT reduced to 1.91 × 10-5, while a similar trend seen (FIG. 3a) in P2 and P3 of the thin film. FIG 3 b summarizes the FET μ P1-P3 is measured, which is extracted from the linear region of the transfer curve. Slowly in CHCl3 – the average moving speed is dried to give 1.75 × 10-1 (P1), 4.50 × 10-4 (P2) and 1.95 × 10-3 cm2 V-1 s-1 (P3). Calculated in these systems the carrier concentration in the range of between 1017 to 1019 cm-3, which is comparable to a heavily doped high-performance system. All samples, under different gate voltage (Vg), and the output curve (FIG. 3c) showed no significant linear and saturated region, the drain current (Id) with a drain voltage (Vd) changes from -60 to 60 sometimes V increases linearly. Under different processing conditions, the film P1 measured variable temperature (160-380 K) with demonstrated temperature [sigma] (Figure 3d) increases, and the following equation σ (T) = σ0exp (-Ea / kBT) .
In CH3Cl slowly dried film P1 GIWAXS shows the structured surface of the outer form higher order diffraction peak, as q ≈ (200), and 0.86 Å-1 at the q ≈ (300) 0.54 Å-1 at, show that the modified layered stacked side chains ( FIG. 4a). Further, when the film P1 are slowly dried in CHCl3 and hexane, a direction out of the plane of the sharper appeared at (d≈12.32 Å) and q≈1.04 Å-1 q ≈ 0.51 Å-1, more narrow a diffraction peak (001) and (002), indicates that the main-chain bulk is enhanced (FIG. 4a-c). Although GIWAXS show very similar in sequence enhanced, but the AFM measurements showed that the film was slowly dried in high performance P1 in CHCl3When dry, RMS roughness of 23.1 nm, there were significant differences (FIG. 4d, e) nanoscale morphology fibrillated structure. Similar structures have higher molecular order, no grain boundaries and enhance transport. From FIG. 4f, g can be seen in hexanes was slowly dried film P1 has a more granular structure and a rough surface having a clear grain boundaries between the domains (RMS roughness = 25.8 nm).
FIG. 5, the narrow band gap neutral investigator, self-doped heteroaryl radical and commercial conductive polymer as a reference, the conductivity of the high-performance thin film P1 comparison, the highest conductivity P1. Meanwhile, in all of the undoped polymer, the film shows a record Pl of σRT, up to 8.18 S cm-1.
In conclusion, the researchers realized without synthetic polymer doped with conductive material comparable with the commercial material, its narrow band gap, open shell structure, strong electron correlation, workability, stability and robust solution provides new opportunities for charge transport molecule in the system, it can implement new features and optoelectronic devices. Original link: https: //doi.org/10.1002/adfm.201909805