RESUMEN
Thermoelectric textile devices represent an intriguing avenue for powering wearable electronics. The lack of air-stable n-type polymers has, until now, prevented the development of n-type multifilament yarns, which are needed for textile manufacturing. Here, the thermomechanical properties of the recently reported n-type polymer poly(benzodifurandione) (PBFDO) are explored and its suitability as a yarn coating material is assessed. The outstanding robustness of the polymer facilitates the coating of silk yarn that, as a result, displays an effective bulk conductivity of 13 S cm-1, with a projected half-life of 3.2 ± 0.7 years at ambient conditions. Moreover, the n-type PBFDO coated silk yarn with a Young's modulus of E = 0.6 GPa and a strain at break of εbreak = 14% can be machine washed, with only a threefold decrease in conductivity after seven washing cycles. PBFDO and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) coated silk yarns are used to fabricate two out-of-plane thermoelectric textile devices: a thermoelectric button and a larger thermopile with 16 legs. Excellent air stability is paired with an open-circuit voltage of 17 mV and a maximum output power of 0.67 µW for a temperature difference of 70 K. Evidently, PBFDO coated multifilament silk yarn is a promising component for the realization of air stable thermoelectric textile devices.
RESUMEN
n-Type polythiophene represents a promising category of n-type polymer thermoelectric materials known for their straightforward structure and scalable synthesis. However, n-type polythiophene often suffers from a twisted backbone and poor stacking property when introducing high-density electron-withdrawing groups for a lower lowest unoccupied molecular orbital (LUMO) level, which is considered to be beneficial for n-doping efficiency. Herein, we developed two isomers of polythiophene derivatives, PTTz1 and PTTz2, by inserting thiazole units into the polythiophene backbone composed of thieno[3,4-c]pyrrole-4,6-dione (TPD) and thiophene-3,4-dicarbonitrile (2CNT). Although PTTz1 and PTTz2 share a similar polymer skeleton, they differ in thiazole configuration, with the nitrogen atoms of the thiazole units oriented toward TPD and 2CNT, respectively. The insertion of thiazole units significantly planarizes the polythiophene backbone while largely preserving low LUMO levels. Notably, PTTz2 exhibits a more coplanar backbone and closer π-stacking compared to PTTz1, resulting in a greatly enhanced electron mobility. Both PTTz1 and PTTz2 can be easily n-doped due to their deep LUMO levels. PTTz2 demonstrates superior thermoelectric performance, with an electrical conductivity of 50.3 S cm-1 and a power factor of 23.8 µW m-1 K-2, which is approximately double that of PTTz1. This study highlights the impact of the thiazole unit on n-type polythiophene derivatives and provides valuable guidelines for the design of high-performance n-type polymer thermoelectric materials.
RESUMEN
Wearable electronic devices have emerged as a pivotal technology in healthcare and artificial intelligence robots. Among the materials that are employed in wearable electronic devices, organic thermoelectric materials possess great application potential due to their advantages such as flexibility, easy processing ability, no working noise, being self-powered, applicable in a wide range of scenarios, etc. However, compared with classic conductive materials and inorganic thermoelectric materials, the research on organic thermoelectric materials is still insufficient. In order to improve our understanding of the potential of organic thermoelectric materials in wearable electronic devices, this paper reviews the types of organic thermoelectric materials and composites, their assembly strategies, and their potential applications in wearable electronic devices. This review aims to guide new researchers and offer strategic insights into wearable electronic device development.
RESUMEN
Poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT: PSS) is a promising material for organic thermoelectric (TE) applications. However, it is challenging to achieve PEDOT: PSS composites with stretchable, self-healable, and high TE performance. Furthermore, some existing self-healing TE materials employ toxic reagents, posing risks to human health and the environment. In this study, a novel intrinsically self-healable and wearable composite is developed by incorporating environmentally friendly, highly biocompatible, and biodegradable materials of polyvinyl alcohol (PVA) and citric acid (CA) into PEDOT: PSS. This results in the formation of double hydrogen bonding networks among CA, PVA, and PEDOT: PSS, inducing microstructure alignment and leading to simultaneous enhancements in both TE performance and stretchability. The resulting composites exhibit a high electrical conductivity and power factor of 259.3 ± 11.7 S·cm-1, 6.9 ± 0.4 µW·m-1·K-2, along with a tensile strain up to 68%. Furthermore, the composites display impressive self-healing ability, with 84% recovery in electrical conductivity and an 85% recovery in tensile strain. Additionally, the temperature and strain sensors based on the PEDOT: PSS/PVA/CA are prepared, which exhibit high resolution suitable for human-machine interaction and wearable devices. This work provides a reliable and robust solution for the development of environmentally friendly, self-healing and wearable TE thermoelectrics.
RESUMEN
Achieving high electrical conductivity (σ) and power factor (PF) simultaneously remains a significant challenge for n-type organic themoelectrics (OTEs). Herein, we demonstrate the state-of-the-art OTEs performance through blending a fused bithiophene imide dimer-based polymer f-BTI2g-SVSCN and its selenophene-substituted analogue f-BSeI2g-SVSCN with a julolidine-functionalized benzimidazoline n-dopant JLBI, vis-à-vis when blended with commercially available n-dopants TAM and N-DMBI. The advantages of introducing a more lipophilic julolidine group into the dopant structure of JLBI are evidenced by the enhanced OTEs performance that JLBI-doped films show when compared to those doped with N-DMBI or TAM. In fact, thanks to the enhanced intermolecular interactions and the lower-lying LUMO level enabled by the increase of selenophene content in polymer backbone, JLBI-doped films of f-BSeI2g-SVSCN exhibit a unprecedent σ of 206â S cm-1 and a PF of 114â µW m-1 K-2. Interestingly, σ can be further enhanced up to 326â S cm-1 by using TAM dopant as a consequence of its favorable diffusion behavior into densely packed crystalline domains. These values are the highest to date for solution-processed molecularly n-doped polymers, demonstrating the effectiveness of the polymer-dopant matching approach carried out in this work.
RESUMEN
Conjugated polymers are emerging as competitive candidates for organic thermoelectrics (OTEs). However, to make the device truly pervasive, both p- and n-type conjugated polymers are essential. Despite great efforts, no n-type equivalents to the p-type benchmark PEDOT:PSS exist to date mainly due to the low electrical conductivity (σ). Herein, a near-amorphous n-type conjugated polymer, namely pDFSe, is reported with high σ by achieving the synergy between charge transport and doping efficiency. The polymer pDFSe is synthesized based on an acceptor-triad moiety of diketopyrrolopyrrole-difluorobenzoselenadiazole-diketopyrrolopyrrole (DFSe), which has the noncovalently-fused-ring structure to reinforce the backbone rigidity. Furthermore, an axisymmetric thiophene-selenophene-thiophene donor is introduced, which enables the formation of near-amorphous microstructures. The above merits ensure good doping efficiency without scarifying efficient intrachain charge-carrier transport. Thus, pDFSe-based n-type transistors exhibit high electron mobility up to 6.15â cm2 V-1 s-1, much higher than its reference polymer pDSe without the noncovalently-fused-ring structure (0.77â cm2 V-1 s-1). Further upon n-doping, pDFSe demonstrates excellent σ of 62.6â S cm-1 and maximum power factor of 133.1â µW m-1 K-2, which are among the highest values reported for solution-processed n-type polymers. The results demonstrate the great potential of near-amorphous n-type conjugated polymers with noncovalently-fused-ring structure for the next-generation OTEs.
RESUMEN
While research on organic thermoelectric polymers is making significant progress in recent years, realization of a single polymer material possessing both thermoelectric properties and stretchability for the next generation of self-powered wearable electronics is a challenging task and remains an area yet to be explored. A new molecular engineering concept of "conjugated breaker" is employed to impart stretchability to a highly crystalline diketopyrrolepyrrole (DPP)-based polymer. A hexacyclic diindenothieno[2,3-b]thiophene (DITT) unit, with two 4-octyloxyphenyl groups substituted at the tetrahedral sp3-carbon bridges, is selected to function as the conjugated breaker that can sterically hinder intermolecular packing to reduce polymers' crystallinity. A series of donor-acceptor random copolymers is thus developed via polymerizing the crystalline DPP units with the DITT conjugated breakers. By controlling the monomeric DPP/DITT ratios, DITT30 reaches the optimal balance of crystalline/amorphous regions, exhibiting an exceptional power factor (PF) value up to 12.5 µW m-1 K-2 after FeCl3-doping; while, simultaneously displaying the capability to withstand strains exceeding 100%. More significantly, the doped DITT30 film possesses excellent mechanical endurance, retaining 80% of its initial PF value after 200 cycles of stretching/releasing at a strain of 50%. This research marks a pioneering achievement in creating intrinsically stretchable polymers with exceptional thermoelectric properties.
RESUMEN
Conjugated polymers are promising materials for thermoelectric applications, however, at present few effective and well-understood strategies exist to further advance their thermoelectric performance. Here a new model system is reported for a better understanding of the key factors governing their thermoelectric properties: aligned, ribbon-phase poly[2,5-bis(3-dodecylthiophen-2-yl)thieno[3,2-b]thiophene] (PBTTT) doped by ion-exchange doping. Using a range of microstructural and spectroscopic methods, the effect of controlled incorporation of tie-chains between the crystalline domains is studied through blending of high and low molecular weight chains. The tie chains provide efficient transport pathways between crystalline domains and lead to significantly enhanced electrical conductivity of 4810 S cm-1, which is not accompanied by a reduction in Seebeck coefficient or a large increase in thermal conductivity. Respectable power factors of 173 µW m-1 K-2 are demonstrated in this model system. The approach is generally applicable to a wide range of semicrystalline conjugated polymers and could provide an effective pathway for further enhancing their thermoelectric properties and overcome traditional trade-offs in optimization of thermoelectric performance.
RESUMEN
Doping is a crucial strategy to enhance the performance of various organic electronic devices. However, in many cases, the random distribution of dopants in conjugated polymers leads to the disruption of the polymer microstructure, severely constraining the achievable performance of electronic devices. Here, it is shown that by ion-exchange doping polythiophene-based P[(3HT)1-x-stat-(T)x] (x = 0 (P1), 0.12 (P2), 0.24 (P3), and 0.36 (P4)), remarkably high electrical conductivity of >400 S cm-1 and power factor of >16 µW m-1 K-2 are achieved for the random copolymer P3, ranking it among highest ever reported for unaligned P3HT-based films, significantly higher than that of P1 (<40 S cm-1, <4 µW m-1 K-2). Although both polymers exhibit comparable field-effect transistor hole mobilities of ≈0.1 cm2 V-1 s-1 in the pristine state, after doping, Hall effect measurements indicate that P3 exhibits a large Hall mobility up to 1.2 cm2 V-1 s-1, significantly outperforming that of P1 (0.06 cm2 V-1 s-1). GIWAXS measurement determines that the in-plane π-π stacking distance of doped P3 is 3.44 Å, distinctly shorter than that of doped P1 (3.68 Å). These findings contribute to resolving the long-standing dopant-induced-disorder issues in P3HT and serve as an example for achieving fast charge transport in highly doped polymers for efficient electronics.
RESUMEN
The general strategy for n-type organic thermoelectric is to blend n-type conjugated polymer hosts with small molecule dopants. In this work, all-polymer n-type thermoelectric is reported by dissolving a novel n-type conjugated polymer and a polymer dopant, poly(ethyleneimine) (PEI), in alcohol solution, followed by spin-coating to give polymer host/polymer dopant blend film. To this end, an alcohol-soluble n-type conjugated polymer is developed by attaching polar and branched oligo (ethylene glycol) (OEG) side chains to a cyano-substituted poly(thiophene-alt-co-thiazole) main chain. The main chain results in the n-type property and the OEG side chain leads to the solubility in hexafluorineisopropanol (HFIP). In the polymer host/polymer dopant blend film, the Coulombic interaction between the dopant counterions and the negatively charged polymer chains is reduced and the ordered stacking of the polymer host is preserved. As a result, the polymer host/polymer dopant blend exhibits the power factor of 36.9 µW m-1 K-1, which is one time higher than that of the control polymer host/small molecule dopant blend. Moreover, the polymer host/polymer dopant blend shows much better thermal stability than the control polymer host/small molecule dopant blend. This research demonstrates the high performance and excellent stability of all-polymer n-type thermoelectric.
RESUMEN
Recent research efforts have concentrated on the development of flexible and stretchable thermoelectric (TE) materials. However, significant challenges have emerged, including increased resistance and reduced electrical conductivity when subjected to strain. To address these issues, rigid semiconducting polymers and elastic insulating polymers have been incorporated and nanoconfinement effects have been exploited to enhance the charge mobility. Herein, a feasible approach is presented for fabricating stretchable TE materials by using a doped semiconducting polymer blend consisting of either poly(3-hexylthiophene) (P3HT) or poly(3,6-dithiophen-2-yl-2,5-di(2-decyltetradecyl)-pyrrolo[3,4-c]pyrrole-1,4-dione-alt-thienylenevinylene-2,5-yl) (PDVT-10) as the rigid polymer with styrene-ethylene-butylene-styrene (SEBS) as the elastic polymer. In particular, the blend composition is optimized to achieve a continuous network structure with SEBS, thereby improving the stretchability. The optimized polymer films exhibit well-ordered microstructural aggregates, indicative of good miscibility with FeCl3 and enhanced doping efficiency. Notably, a lower activation energy and higher charge-carrier concentration contribute to an improved electrical conductivity under high tensile strain, with a maximum output power of 1.39 nW at a ΔT of 22.4 K. These findings offer valuable insights and serve as guidelines for the development of stretchable p-n junction thermoelectric generators based on doped semiconducting polymer blends with potential applications in wearable electronics and energy harvesting.
RESUMEN
Developing low-cost and high-performance n-type polymer semiconductors is essential to accelerate the application of organic thermoelectrics (OTEs). To achieve this objective, it is critical to design strong electron-deficient building blocks with simple structure and easy synthesis, which are essential for the development of n-type polymer semiconductors. Herein, we synthesized two cyano-functionalized highly electron-deficient building blocks, namely 3,6-dibromopyrazine-2-carbonitrile (CNPz) and 3,6-Dibromopyrazine-2,5-dicarbonitrile (DCNPz), which feature simple structures and facile synthesis. CNPz and DCNPz can be obtained via only one-step reaction and three-step reactions from cheap raw materials, respectively. Based on CNPz and DCNPz, two acceptor-acceptor (A-A) polymers, P(DPP-CNPz) and P(DPP-DCNPz) are successfully developed, featuring deep-positioned lowest unoccupied molecular orbital (LUMO) energy levels, which are beneficial to n-type organic thin-film transistors (OTFTs) and OTEs performance. An optimal unipolar electron mobility of 0.85 and 1.85â cm2 V-1 s-1 is obtained for P(DPP-CNPz) and P(DPP-DCNPz), respectively. When doped with N-DMBI, P(DPP-CNPz) and P(DPP-DCNPz) show high n-type electrical conductivities/power factors of 25.3â S cm-1 /41.4â µW m-1 K-2 , and 33.9â S cm-1 /30.4â µW m-1 K-2 , respectively. Hence, the cyano-functionalized pyrazine CNPz and DCNPz represent a new class of structurally simple, low-cost and readily accessible electron-deficient building block for constructing n-type polymer semiconductors.
RESUMEN
Rational design, synthesis, and characterization of a new efficient versatile n-type dopant with a closed-shell electronic structure are described. By employing the tetraphenyl-dipyranylidene (DP0) framework with two 7π-electron systems modified with N,N-dimethylamino groups as the strong electron-donating substituent, 2,2',6,6'-tetrakis[4-(dimethylamino)phenyl]-4,4'-dipyranylidene (DP7), a closed-shell molecule with an extremely high-lying energy level of the highest occupied molecular orbital, close to 4.0 eV below the vacuum level, is successfully developed. Thanks to its thermal stability, DP7 is applicable to vacuum deposition, which allows utilization of DP7 in bulk doping for the development of n-type organic thermoelectric materials and contact doping for reducing contact resistance in n-type organic field-effect transistors. As vacuum-deposition processable n-type dopants are very limited, DP7 stands out as a useful n-type dopant, particularly for the latter purpose.
RESUMEN
Developing high-performance n-type polymer mixed ionic-electronic conductors (PMIECs) is a grand challenge, which largely determines their applications in vaious organic electronic devices, such as organic electrochemical transistors (OECTs) and organic thermoelectrics (OTEs). Herein, two halogen-functionalized PMIECs f-BTI2g-TVTF and f-BTI2g-TVTCl built from fused bithiophene imide dimer (f-BTI2) as the acceptor unit and halogenated thienylene-vinylene-thienylene (TVT) as the donor co-unit are reported. Compared to the control polymer f-BTI2g-TVT, the fluorinated f-BTI2g-TVTF shows lower-positioned lowest unoccupied molecular orbital (LUMO), improved charge transport property, and greater ion uptake capacity. Consequently, f-BTI2g-TVTF delivers a state-of-the-art µC* of 90.2 F cm-1 V-1 s-1 with a remarkable electron mobility of 0.41 cm2 V-1 s-1 in OECTs and an excellent power factor of 64.2 µW m-1 K-2 in OTEs. An OECT-based inverter amplifier is further demonstrated with voltage gain up to 148 V V-1 , which is among the highest values for OECT inverters. Such results shed light on the impacts of halogen atoms on developing high-performing n-type PMIECs.
RESUMEN
Developing polymers with high electrical conductivity (σ) after n-doping is a great challenge for the advance of the field of organic thermoelectrics (OTEs). Herein, we report a series of thiazole imide-based n-type polymers by gradually increasing selenophene content in polymeric backbone. Thanks to the strong intramolecular noncovalent Nâ â â S interaction and enhanced intermolecular Seâ â â Se interaction, with the increase of selenophene content, the polymers show gradually lowered LUMOs, more planar backbone, and improved film crystallinity versus the selenophene-free analogue. Consequently, polymer PDTzSI-Se with the highest selenophene content achieves a champion σ of 164.0â S cm-1 and a power factor of 49.0â µW m-1 K-2 in the series when applied in OTEs after n-doping. The σ value is the highest one for n-type donor-acceptor OTE materials reported to date. Our work indicates that selenophene substitution is a powerful strategy for developing high-performance n-type OTE materials and selenophene incorporated thiazole imides offer an excellent platform in enabling n-type polymers with high backbone coplanarity, deep-lying LUMO and enhanced mobility/conductivity.
RESUMEN
The ability of n-type polymer thermoelectric materials to tolerate high doping loading limits further development of n-type polymer conductivity. Herein, two alcohol-soluble n-type polythiophene derivatives that are n-PT3 and n-PT4 are reported. Due to the ability of two polymers to tolerate doping loading more significantly than 100 mol%, both achieve electrical conductivity >100 S cm-1 . Moreover, the conductivity of both polythiophenes remains almost constant at high doping concentrations with excellent doping tunability, which may be related to their ability to overcome charging-induced backbone torsion and morphology change caused by saturated doping. The characterizations reveal that n-PT4 has a high doping level and carrier concentration (>3.10 × 1020 cm-3 ), and the carrier concentration continues to increase as the doping concentration increases. In addition, doping leads to improved crystal structure of n-PT4, and the crystallinity does not decrease significantly with increasing doping concentration; even the carrier mobility increases with it. The synergistic effect of these two leads to both n-PT3 and n-PT4 achieving a breakthrough of 100 in conductivity and power factor. The DMlmC-doped n-PT4 achieves a power factor of over 150 µW m-1 K-2 . These values are among the highest for n-type organic thermoelectric materials.
RESUMEN
Here, we examine the impact of the molecular weight of an n-type conjugated polymer (n-PT2) on molecular doping and thermoelectric parameters. Two common dopants TDAE and N-DMBI with different doping mechanisms are used for molecular doping of n-PT2. It turns out that n-PT2 with a higher molecular weight is more miscible with the dopant, leading to more charge carriers. Moreover, the crystal structures and morphology of n-PT2 with a higher molecular weight are more tolerant against the intrusion of dopant molecules and charging. Finally, these factors work in synergy to endow the doped n-PT2 with the best conductivity and power factor (144 S cm-1/75.0 µW m-1 K-2 and 75.4 S cm-1/98.5 µW m-1 K-2 after doping by TDAE and N-DMBI, respectively). This study indicates that regulating the molecular weight allows for synergistic regulation of conductivity and Seebeck coefficient and is a feasible means to improve the performance for a given n-type organic thermoelectric material.
RESUMEN
n-Doped polymers with high electrical conductivity (σ) are still very scarce in organic thermoelectrics (OTEs), which limits the development of efficient organic thermoelectric generators. A series of fused bithiophene imide dimer-based polymers, PO8, PO12, and PO16, incorporating distinct oligo(ethylene glycol) side-chain to optimize σ is reported here. Three polymers show a monotonic electron mobility decrease as side-chain size increasing due to the gradually lowered film crystallinity and change of backbone orientation. Interestingly, polymer PO12 with a moderate side-chain size delivers a champion σ up to 92.0 S cm-1 and a power factor (PF) as high as 94.3 µW m-1 K-2 in the series when applied in OTE devices. The PF value is among the highest ones for the solution-processing n-doped polymers. In-depth morphology studies unravel that the moderate crystallinity and the formation of 3D conduction channel derived from bimodal orientation synergistically contribute to high doping efficiency and large charge carrier mobility, thus resulting in high performance for the PO12-based OTEs. The results demonstrate the great power of simple tuning of side chain in developing n-type polymers with substantial σ for improving organic thermoelectric performance.
RESUMEN
Doped n-type polymers usually exhibit low electrical conductivities and thermoelectric power factors (PFs), restricting the development of high-performance p-n-junction-based organic thermoelectrics (OTEs). Herein, the design and synthesis of a new cyano-functionalized fused bithiophene imide dimer (f-BTI2), CNI2, is reported, which synergistically combines the advantages of both cyano and imide functionalities, thus leading to substantially higher electron deficiency than the parent f-BTI2. On the basis of this novel building block, a series of n-type donor-acceptor and acceptor-acceptor polymers are successfully synthesized, all of which show good solubility, deep-lying frontier molecular orbital levels, and favorable polymer chain orientation. Among them, the acceptor-acceptor polymer PCNI2-BTI delivers an excellent electrical conductivity up to 150.2 S cm-1 and a highest PF of 110.3 µW m-1 K-2 in n-type OTEs, attributed to the optimized polymer electronic properties and film morphology with improved molecular packing and higher crystallinity assisted by solution-shearing technology. The PF value is the record of n-type polymers for OTEs to date. This work demonstrates a facile approach to designing high-performance n-type polymers and fabricating high-quality films for OTE applications.
RESUMEN
Typical n-type conjugated polymers are based on fused-ring electron-accepting building blocks. Herein, we report a non-fused-ring strategy to design n-type conjugated polymers, i.e. introducing electron-withdrawing imide or cyano groups to each thiophene unit of a non-fused-ring polythiophene backbone. The resulting polymer, n-PT1, shows low LUMO/HOMO energy levels of -3.91â eV/-6.22â eV, high electron mobility of 0.39â cm2 â V-1 s-1 and high crystallinity in thin film. After n-doping, n-PT1 exhibits excellent thermoelectric performance with an electrical conductivity of 61.2â S cm-1 and a power factor (PF) of 141.7â µW m-1 K-2 . This PF is the highest value reported so far for n-type conjugated polymers and this is the first time for polythiophene derivatives to be used in n-type organic thermoelectrics. The excellent thermoelectric performance of n-PT1 is due to its superior tolerance to doping. This work indicates that polythiophene derivatives without fused rings are low-cost and high-performance n-type conjugated polymers.