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![Isoindigo‐derived polymers for thermoelectric applications. a) Molecular structures of P157–P159. b) Electrical conductivities and c) power factors of doped P157–P159. (b,c) Reproduced with permission.[¹⁹⁷] Copyright 2015, American Chemical Society. d) Simulations of the backbone conformation of P115 in side‐chain‐disordered and non‐interdigitated structures (left). Electron effective mass obtained from the theoretical calculations. Band structures and partial densities of states of the polymer (right). Spin density distributions of the polymer (n = 6) as calculated by UwB97XD/6‐311g (d,p) (bottom). e) Conductivity of the doped polymers at different concentrations of the dopant N‐DMBI. f) Seebeck coefficients and power factors of P115 for different dopant ratios. (d–f) Reproduced with permission.[⁷²] Copyright 2019, Wiley‐VCH. g) Molecular structure of P160. h) AFM height images of pristine (left), 5 wt% doped (middle), and 30 wt% doped (right) P160 films. h) Reproduced with permission.[²⁰⁰] Copyright 2020, American Chemical Society. i) Molecular structure of P161. j) Schematic of TAM‐doped P161 film. The film exhibited low ionization, high carrierization properties, which contributes to the high thermoelectric performance. j) Reproduced with permission.[²⁰¹] Copyright 2020, American Chemical Society.](publication/349838093/figure/fig13/AS:11431281172988989@1688736283434/Isoindigo-derived-polymers-for-thermoelectric-applications-a-Molecular-structures-of.png)
Isoindigo‐derived polymers for thermoelectric applications. a) Molecular structures of P157–P159. b) Electrical conductivities and c) power factors of doped P157–P159. (b,c) Reproduced with permission.[¹⁹⁷] Copyright 2015, American Chemical Society. d) Simulations of the backbone conformation of P115 in side‐chain‐disordered and non‐interdigitated structures (left). Electron effective mass obtained from the theoretical calculations. Band structures and partial densities of states of the polymer (right). Spin density distributions of the polymer (n = 6) as calculated by UwB97XD/6‐311g (d,p) (bottom). e) Conductivity of the doped polymers at different concentrations of the dopant N‐DMBI. f) Seebeck coefficients and power factors of P115 for different dopant ratios. (d–f) Reproduced with permission.[⁷²] Copyright 2019, Wiley‐VCH. g) Molecular structure of P160. h) AFM height images of pristine (left), 5 wt% doped (middle), and 30 wt% doped (right) P160 films. h) Reproduced with permission.[²⁰⁰] Copyright 2020, American Chemical Society. i) Molecular structure of P161. j) Schematic of TAM‐doped P161 film. The film exhibited low ionization, high carrierization properties, which contributes to the high thermoelectric performance. j) Reproduced with permission.[²⁰¹] Copyright 2020, American Chemical Society.
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The past few decades have witnessed the tremendous development of semiconducting polymers in electronic applications, which is inextricably related to the diversity of polymer structure. The change of polymer structure significantly influences the polymer packing, thin film morphology, and other optoelectronic properties, thus meeting the need for...
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... [69] Since then, numerous studies have proved that this unit was easy to be modified and had great potential to be widely applied. [28] Fluorination is one of the effective methods to afford high performance polymer semiconductors. Fluorinated isoindigo based polymer, P27, was first synthesized by Pei and the co-workers. ...
In recent years, conjugated polymers have received widespread attention due to their characteristic advantages of light weight, favorable solution processability, and structural modifiability. Among various conjugated polymers, fluorinated ones have developed rapidly to achieve high‐performance n‐type or ambipolar polymeric semiconductors. The uniqueness of fluorinated conjugated polymers contains the high coplanarity of their structures, lower frontier molecular orbital energy levels, and strong nonbonding interactions. In this review, first the fluorinated building blocks, including fluorinated benzene and thiophene rings, fluorinated B←N bridged units, and fluoroalkyl side chains are summarized. Subsequently, different synthetic methods of fluorinated conjugated polymers are described, with a special focus on their respective advantages and disadvantages. Then, with these numerous fluorinated structures and appropriate synthetic methods bear in mind, the properties and applications of the fluorinated conjugated polymers, such as cyclopentadithiophene‐, amide‐, and imide‐based polymers, and B←N embedded polymers, are systematically discussed. The introduction of fluorine atoms can further enhance the electron‐deficiency of the backbone, influencing the charge carrier transport performance. The promising fluorinated conjugated polymers are applied widely in organic field‐effect transistors, organic solar cells, organic thermoelectric devices, and other organic opto‐electric devices. Finally, the outlook on the challenges and future development of fluorinated conjugated polymers is systematically discussed.
... Therefore, excellent but limited strong electron acceptors such as benzobisthiadiazole, thiadiazoloquinoxaline, triazoloquinoxaline, diketopyrrolopyrrole, isoinidigo and their derivatives have been frequently used. [21][22][23][24][25][26] More recently, novel acceptor building blocks such as imide-functionalized fluorenones [27] and d π -p π conjugated di-metallaaromatics were developed. [28] However, due to their highly planar structures, aggregation-caused quenching (ACQ) caused by intra/interchain π-π stacking interaction in condensed states frequently occurred and poor luminescent properties were observed in films and NPs. ...
Luminescence in the second near‐infrared (NIR‐II, 1,000–1,700 nm) window is beneficial especially for deep tissue imaging and optical sensors because of intrinsic high permeability through various media. Strong electron‐acceptors with low‐lying lowest unoccupied molecular orbital (LUMO) energy levels are a crucial unit for donor–acceptor (D–A) π‐conjugated polymers (CPs) with the NIR‐II emission property, however, limited kinds of molecular skeletons are still available. Herein, D–A CPs involving fluorinated boron‐fused azobenzene complexes (BAz) with enhanced electron‐accepting properties are reported. Combination of fluorination at the azobenzene ligand and trifluoromethylation at the boron can effectively lower the LUMO energy level down to −4.42 eV, which is much lower than those of conventional strong electron‐acceptors. The synthesized series of CPs showed excellent absorption/fluorescence property in solution over a wide NIR range including NIR‐II. Furthermore, owing to the inherent solid‐state emissive property of the BAz skeleton, obvious NIR‐II fluorescence from the film (up to λFL=1213 nm) and the nanoparticle in water (λFL=1036 nm, brightness=up to 29 cm⁻¹ M⁻¹) were observed, proposing that our materials are applicable for developing next‐generation of NIR‐II luminescent materials.
... Isoindigo and its derivatives have been extensively utilised as core building blocks in organic semiconductors [25][26][27][28] , but have rarely been explored as redox molecules for organic electrodes. We envisage isoindigos bearing α,β-unsaturated 1,4-diketone functionalities to be redox-active and can complex with CO 2 at the oxygen centres in the reduced state. ...
... This is likely due to the charge-transfer effect that lowers the energy level of the molecule, offsetting the electronic effect from EDGs. Specifically, isoindigo species are electron acceptors (n-type organic semiconductors) 28 , where charge transfer can be induced between the electron-deficient isoindigo rings and the electron-rich methoxy group. UV-vis absorption spectra suggest an optical bandgap of 1.90~1.98 ...
Efficient CO2 separation technologies are essential for mitigating climate change. Compared to traditional thermochemical methods, electrochemically mediated carbon capture using redox-tunable sorbents emerges as a promising alternative due to its versatility and energy efficiency. However, the undesirable linear free-energy relationship between redox potential and CO2 binding affinity in existing chemistry makes it fundamentally challenging to optimise key sorbent properties independently via chemical modifications. Here, we demonstrate a design paradigm for electrochemically mediated carbon capture sorbents, which breaks the undesirable scaling relationship by leveraging intramolecular hydrogen bonding in isoindigo derivatives. The redox potentials of isoindigos can be anodically shifted by >350 mV to impart sorbents with high oxygen stability without compromising CO2 binding, culminating in a system with minimised parasitic reactions. With the synthetic space presented, our effort provides a generalisable strategy to finetune interactions between redox-active organic molecules and CO2, addressing a longstanding challenge in developing effective carbon capture methods driven by non-conventional stimuli.
... In this content, we focused on thienoisoindigo (TII), 46,47 a thiophene-based analogue of isoindigo (IIG), 48,49 as the recoverable monomer. Both TII and IIG monomers have been extensively used to synthesize semiconducting polymers for organic electronics, [50][51][52][53][54] with a TII-based copolymer reported to have a hole-transporting field-effect transistor (FET) mobility of 10 cm 2 V −1 s −1 . 55 In contrast to TDPP monomers, we found that TII monomers do not decompose in the presence of neat trifluoroacetic acid (TFA), a desirable characteristic for imine-based polymers that degrade under acidic conditions (Fig. 1). ...
Imine-based semiconducting polymers based on thiophene-flanked diketopyrrolopyrrole (TDPP) are widely used to realize naturally disposable electronic devices. However, TDPP easily decomposes under mildly acidic conditions, limiting its potential for use in recyclable systems. Herein, we designed and synthesized two chemically recyclable thienoisoindigo (TII)-based polymers bearing an imine bond. These polymers were prepared from polycondensation reactions of the dialdehyde-functionalized monomer TII-(CHO)2 with p-phenylenediamine (PD) to produce p(TII-PD) and with 2,6-naphthalenediamine (2,6ND) to produce p(TII-2,6ND), respectively. Using ultraviolet-visible-near infrared spectroscopy, nuclear magnetic resonance, and mass spectroscopy, we examined the recyclability of both polymers. Under mildly acidic conditions, the imine-based polymers fully degrade into the original TII-(CHO)2 in as little as one day. Moreover, the recovered TII-(CHO)2 monomer is chemically stable for up to 6 months under acidic conditions, allowing us to isolate the monomer in high yield (>90%). Using the recovered TII-(CHO)2 monomer, we prepared recycled polymers, re-p(TII-PD) and re-p(TII-2,6ND). The recycled polymers displayed nearly the same electrical properties as the pristine polymers, with field-effect transistor mobilities in the order of 10⁻²–10⁻³ cm² V⁻¹ s⁻¹. These results demonstrate the versatility of the TII-based monomer unit for developing fully recyclable semiconducting polymers.
... The extra carbonyl group in the imine portion makes NDI more electronegative than those of lactamcontaining DPPs. [70] The multi-aromatic ring structure with the double electron-absorbing imine functional groups makes NDI an ideal electron A unit for the construction of semiconducting D−A type COFs. ...
Covalent organic frameworks (COFs) are new organic porous materials constructed by covalent bonds, with the advantages of pre‐designable topology, adjustable pore size and abundant active sites. Many research studies have shown that COFs exhibit great potential in gas adsorption, molecular separation, catalysis, drug delivery, energy storage, etc. However, the electrons and holes of intrinsic COF are prone to compounding in transport, and the carrier lifetime is short. The donor‐acceptor (D−A) type COFs, which are synthesized by introducing D and A units into the COFs backbone, combine separated electron and hole migration pathway, tunable band gap and optoelectronic properties of D‐A type polymers with the unique advantages of COFs and have made great progress in related research in recent years. Here, the synthetic strategies of D−A type COFs are firstly outlined, including the rational design of linkages and D−A units as well as functionalization approaches. Then the applications of D−A type COFs in catalytic reactions, photothermal therapy and electronic materials are systematically summarized. In the final section, the current challenges, and new directions for the development of D−A type COFs are presented.
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... It is now recognized as a pioneering direction for future research in this domain, offering significant advantages over traditional metal-catalyzed polymerization methods. [6] It stands out as a costeffective and sustainable approach, avoiding the need for expensive metals and producing water as a byproduct, making it environmentally friendly. Moreover, aldol condensation allows for the synthesis of unique structures, particularly continuous double-and-single-bond linked halffused polymers and double-bond linked rigid-rod fused polymers, which are unattainable through conventional metal-catalyzed methods (Figure 1a). ...
Aldol condensation is a cost‐effective and sustainable synthetic method, offering the advantages of low complexity, substrate universality, and high efficiency. Over the past decade, it has become popular for creating next‐generation organic functional materials, particularly rigid‐rod conjugated (semi)conductors. This review focuses on conjugated small molecules, oligomers, and polymeric (semi)conductors synthesized through aldol condensation, with emphasis on their remarkable features in advancing n‐type organic field‐effect transistors (OFETs), organic electrochemical transistors (OECTs), organic photovoltaics (OPVs), and organic thermoelectrics (OTEs) as well as NIR‐II photothermal conversion. Coherence character, optical properties, microstructure, and chain conformation are investigated to understand material‐property relationships. Future applications and challenges in this area are also discussed.
... [8][9][10][11] Nonetheless, it is required to enhance the performance of both p-type and n-type organic semiconductors at the same time to implement diverse organic electronics applications. [10][11][12][13] Hence, there is a vital requirement for the development of high-mobility n-type organic semiconductors that can perform at ambient conditions. ...
... The rationale behind choosing the isoindigo acceptor unit in our CMPs is because of its proven excellent properties including low-lying frontier molecular orbital (FMO) energy levels, backbone planarity and extended conjugation, a large local dipole, good solubility after N-alkylation, and the ease of synthesis on a large scale. [8,13] To achieve the optimum stacking and flexibility for the fabrication of the CMPs, we opted to N-alkylate the isoindigo unit with a hexyl side chain. [8,13] The current work offers an appealing synthetic chemistry for making 2D-CMPs with high electron mobility, conductivity, and the useful fabrication of thin films, which has a wide range of potential applications in thin-film optoelectronic devices. ...
... [8,13] To achieve the optimum stacking and flexibility for the fabrication of the CMPs, we opted to N-alkylate the isoindigo unit with a hexyl side chain. [8,13] The current work offers an appealing synthetic chemistry for making 2D-CMPs with high electron mobility, conductivity, and the useful fabrication of thin films, which has a wide range of potential applications in thin-film optoelectronic devices. This work sheds light on the fundamental understanding of the donor-acceptor interaction required to elucidate relationships between the structureelectronic properties by using an adequate combination of first-principles calculations with the deformation potential (DP) formalism, which might facilitate the progress of organic semiconducting materials in new directions. ...
The development of n‐type organic semiconductors has evolved significantly slower in comparison to that of p‐type organic semiconductors mainly due to the lack of electron‐deficient building blocks with stability and processability. However, to realize a variety of organic optoelectronic devices, high‐performance n‐type polymer semiconductors are essential. Herein, conjugated microporous polymers (CMPs) comprising isoindigo acceptor units linked to benzene or pyrene donor units (BI and PI) showing n‐type semiconducting behavior are reported. In addition, considering the challenges of deposition of a continuous and homogeneous thin film of CMPs for accurate Hall measurements, a plasma‐assisted fabrication technique is developed to yield uniform thin films. The fully conjugated 2D networks in PI‐ and BI‐CMP films display high electron mobility of 6.6 and 3.5 cm² V⁻¹ s⁻¹, respectively. The higher carrier concentration in PI results in high conductivity (5.3 mS cm⁻¹). Both experimental and computational studies are adequately combined to investigate structure–property relations for this intriguing class of materials in the context of organic electronics.
... For instance, donor-acceptor conjugated polymers based on IID derivatives showed hole and electron mobilities of up to 14.40 and 16.07 cm 2 V −1 s −1 , respectively [1,2]. The power conversion efficiencies of solar cells based on IID-polymer solar cells and IID small molecules exceed 10% and 8%, respectively [3,4]. Furthermore, various IID-based polymers have been used for other applications, such as chemical sensors, organic electrochemical transistors, organic phototransistors, organic thermoelectric generators, etc. [5][6][7][8][9]. ...
Isoindigo (IID) is widely used as a building block for the fabrication of organic semiconductor devices. Understanding the impact of cross-conjugation and linear conjugation on the optoelectronic properties of disubstituted IID is of great importance for the design of improved materials. In this study, phenyl and thienyl groups were substituted at the cross-conjugated 7,7′ position of IID to generate three novel organic semiconductor structures with a donor–acceptor architecture. The optoelectronic properties of this IID derivative were investigated and compared with those of the 6,6′ linearly conjugated IID analogs using UV–Vis spectroscopy and cyclic voltammetry. The experimental results were compared using density functional theory calculations to provide structure–property relationships based on substitution types and attachment sites for IID. The frontier orbital energy levels of the material did not vary dramatically with the position of the substituent, while the type of substituent showed a more significant influence on the HOMO’s energy level and oscillator strength. Phenyl-disubstituted 7,7′ IID (7Ph7′Ph) and thienyl-disubstituted 7,7′ IID (7Th7′Th) materials were used as electron transport layers in perovskite solar cells with a power conversion efficiency of 5.70% and 6.07%, respectively. These observations enhance our understanding of the electronic structure and optoelectronic properties of IID, guiding the design of the next generation of IID-based semiconductors.
... The edge-on orientation can facilitate lateral charge carrier transport in OFETs, but the bimodal orientation is also favorable for charge carrier transport in OFETs, in that the three-dimensional charge carrier transport happens in OFETs. 39,40 The GIWAXS pattern of P29DPP-TT film spin-coated on SAM-treated substrate revealed (h00) and (010) peaks at q ≈ 0.214, 0.431, 0.641, 0.853, and 1.072 Å −1 , and q ≈ 1.82 Å −1 , giving d-spacing and π−π stacking distances of 29.4 and 3.45 Å, respectively ( Figure S4b). However, the (h00) peaks in the scattering patterns of EHD-printed polymer films appeared at lower q values compared to those of spin-coated polymer films, indicating that the d-spacing was increased. ...
... [7][8][9] In the search of efficient polymeric materials for organicelectronics, synthesis of donor-acceptor conjugated polymers has been the most widely approach utilized to date. Several electron-accepting building blocks, such as diketopyrrolopyrrole (DPP), 10,11 cyclic imides, 12,13 benzothiadizole (BT), [14][15][16] and isoindigo (IIG), 17 have demonstrated to be important units and quite efficient. The combination of these acceptor units with different electrondonating groups have yielded either p-type or n-type polymers with hole and electron mobilities now exceeding 14 cm 2 V -1 s -1 . ...
... To the best of our knowledge, this is one of the best balanced ambipolar performance in terms of the electron and hole mobilities among the solution processed OFETs fabricated with IIG-based polymers in a BG-TC device structure. 17,[40][41][42][43] However, further extended fluorination degree in P4 reduces OFET performance, with hole mobilities nearly 5-fold higher than electron mobilities (0.07 vs 0.01 cm 2 V −1 s −1 , respectively), even though the lower energy levels and the slightly increased coplanarity than those of P3. This fact suggests that other factors such as solid-state morphology are also influencing the charge transport properties. ...
We report here the synthesis and physico-chemical characterization of a series of donor-acceptor (D-A) copolymers consisting of 4,7-di(2-thienyl)-2,1,3-benzothiadiazole and isoindigo building blocks, which has been progressively fluorinated with the aim...
