351 results found
Electronic doping in organic materials has remained an elusive concept for several decades. It drew considerable attention in the early days in the quest for organic materials with high electrical conductivity, paving the way for the pioneering work on pristine organic semiconductors (OSCs) and their eventual use in a plethora of applications. Despite this early trend, however, recent strides in the field of organic electronics have been made hand in hand with the development and use of dopants to the point that are now ubiquitous. Here, we give an overview of all important advances in the area of doping of organic semiconductors and their applications. We first review the relevant literature with particular focus on the physical processes involved, discussing established mechanisms but also newly proposed theories. We then continue with a comprehensive summary of the most widely studied dopants to date, placing particular emphasis on the chemical strategies toward the synthesis of molecules with improved functionality. The processing routes toward doped organic films and the important doping-processing-nanostructure relationships, are also discussed. We conclude the review by highlighting how doping can enhance the operating characteristics of various organic devices.
Lin Y-H, Han Y, Sharma A, et al., 2021, A Tri-Channel Oxide Transistor Concept for the Rapid Detection of Biomolecules Including the SARS-CoV-2 Spike Protein, ADVANCED MATERIALS, ISSN: 0935-9648
Allen JDW, Adlem K, Heeney M, 2021, The synthesis and application of novel benzodithiophene based reactive mesogens with negative wavelength dispersion birefringence, JOURNAL OF MATERIALS CHEMISTRY C, ISSN: 2050-7526
Allen TG, Kafourou P, Larson BW, et al., 2021, Reconciling the Driving Force and the Barrier to Charge Separation in Donor-Nonfullerene Acceptor Films, ACS ENERGY LETTERS, Vol: 6, Pages: 3572-3581, ISSN: 2380-8195
Pletzer M, Plasser F, Rimmele M, et al., 2021, [184.108.40.206]Paracyclophanetetraenes (PCTs): cyclic structural analogues of poly(p‑phenylene vinylene)s (PPVs), Open Research Europe, Vol: 1, Pages: 1-12, ISSN: 2732-5121
Background: Poly(p-phenylene vinylene)s (PPVs) and [220.127.116.11]paracyclophanetetraene (PCT) are both composed of alternating π-conjugated para-phenylene and vinylene units. However, while the former constitute a class of π-conjugated polymers that has been used in organic electronics for decades, the latter is a macrocycle that only recently revealed its potential for applications such as organic battery electrodes. The cyclic structure endows PCT with unusual properties, and further tuning of these may be required for specific applications. Methods: In this article, we adopt an approach often used for tuning the properties of PPVs, the introduction of alkoxy (or alkylthio) substituents at the phenylene units, for tuning the optoelectronic properties of PCT. The resulting methoxy- and methylthio-substituted PCTs, obtained by Wittig cyclisation reactions, are studied by UV-vis absorption, photoluminescence, and cyclic voltammetry measurements, and investigated computationally using the visualisation of chemical shielding tensors (VIST) method. Results: The measurements show that substitution leads to slight changes in terms of absorption/emission energies and redox potentials while having a pronounced effect on the photoluminescence intensity. The computations show the effect of the substituents on the ring currents and chemical shielding and on the associated local and global (anti)aromaticity of the macrocycles, highlighting the interplay of local and global aromaticity in various electronic states. Conclusions: The study offers interesting insights into the tuneability of the properties of this versatile class of π-conjugated macrocycles.
Huang Y, Lukito Tjhe DH, Jacobs IE, et al., 2021, Design of experiment optimization of aligned polymer thermoelectrics doped by ion-exchange, Applied Physics Letters, Vol: 119, ISSN: 0003-6951
Organic thermoelectrics offer the potential to deliver flexible, low-cost devices that can directly convert heat to electricity. Previous studies have reported high conductivity and thermoelectric power factor in the conjugated polymer poly[2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene] (PBTTT). Here, we investigate the thermoelectric properties of PBTTT films in which the polymer chains were aligned uniaxially by mechanical rubbing, and the films were doped by a recently developed ion exchange technique that provides a choice over the counterions incorporated into the film, allowing for more optimized morphology and better stability than conventional charge transfer doping. To optimize the polymer alignment process, we took advantage of two Design of Experiment (DOE) techniques: regular two-level factorial design and central composite design. Rubbing temperature Trub and post-alignment annealing temperature Tanneal were the two factors that were most strongly correlated with conductivity. We were able to achieve high polymer alignment with a dichroic ratio >15 and high electrical conductivities of up to 4345 S/cm for transport parallel to the polymer chains, demonstrating that the ion exchange method can achieve conductivities comparable/higher than conventional charge transfer doping. While the conductivity of aligned films increased by a factor of 4 compared to unaligned films, the Seebeck coefficient (S) remained nearly unchanged. The combination of DOE methodology, high-temperature rubbing, and ion exchange doping provides a systematic, controllable strategy to tune structure-thermoelectric property relationships in semiconducting polymers.
Dey S, Attar S, Manley EF, et al., 2021, Transition-Metal-Free Homopolymerization of Pyrrolo[2,3-d:5,4-d']bisthiazoles via Nucleophilic Aromatic Substitution, ACS APPLIED MATERIALS & INTERFACES, Vol: 13, Pages: 41094-41101, ISSN: 1944-8244
Ding B, Kim G, Kim Y, et al., 2021, Influence of Backbone Curvature on the Organic Electrochemical Transistor Performance of Glycolated Donor–Acceptor Conjugated Polymers, Angewandte Chemie, Vol: 133, Pages: 19831-19836, ISSN: 0044-8249
Brabec CJ, Heeney M, Kim Y, et al., 2021, Preface to the Special Issue of ChemSusChem on Advanced Organic Solar Cells, CHEMSUSCHEM, Vol: 14, Pages: 3426-3427, ISSN: 1864-5631
Ding B, Kim G, Kim Y, et al., 2021, Influence of Backbone Curvature on the Organic Electrochemical Transistor Performance of Glycolated Donor-Acceptor Conjugated Polymers, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, Vol: 60, Pages: 19679-19684, ISSN: 1433-7851
Rimmele M, Nogala W, Seif-Eddine M, et al., 2021, Functional group introduction and aromatic unit variation in a set of π‑conjugated macrocycles: revealing the central role of local and global aromaticity, Organic Chemistry Frontiers, Vol: 8, Pages: 4730-4745, ISSN: 2052-4110
π-Conjugated macrocycles are molecules with unique properties that are increasingly exploited for applications and the question of whether they can sustain global aromatic or antiaromatic ring currents is particularly intriguing. However, there are only a small number of experimental studies that investigate how the properties of π‑conjugated macrocycles evolve with systematic structural changes. Here, we present such a systematic experimental study of a set of [18.104.22.168]cyclophanetetraenes, all with formally Hückel antiaromatic ground states, and combine it with an in-depth computational analysis. The study reveals the central role of local and global aromaticity for rationalizing the observed optoelectronic properties, ranging from extremely large Stokes shifts of up to 1.6 eV to reversible fourfold reduction, a highly useful feature for charge storage/accumulation applications. A recently developed method for the visualization of chemical shielding tensors (VIST) is applied to provide unique insight into local and global ring currents occurring in different planes along the macrocycle. Conformational changes as a result of the structural variations can further explain some of the observations. The study contributes to the development of structure–property relationships and molecular design guidelines and will help to understand, rationalize, and predict the properties of other π‑conjugated macrocycles.
Yoo D-J, Heeney M, Glocklhofer F, et al., 2021, Tetradiketone macrocycle for divalent aluminium ion batteries, Nature Communications, Vol: 12, Pages: 1-9, ISSN: 2041-1723
Contrary to early motivation, the majority of aluminium ion batteries developed to date do not utilise multivalent ion storage; rather, these batteries rely on monovalent complex ions for their main redox reaction. This limitation is somewhat frustrating because the innate advantages of metallic aluminium such as its low cost and high air stability cannot be fully taken advantage of. Here, we report a tetradiketone macrocycle as an aluminium ion battery cathode material that reversibly reacts with divalent (AlCl2+) ions and consequently achieves a high specific capacity of 350 mAh g−1 along with a lifetime of 8000 cycles. The preferred storage of divalent ions over their competing monovalent counterparts can be explained by the relatively unstable discharge state when using monovalent AlCl2+ ions, which exert a moderate resonance effect to stabilise the structure. This study opens an avenue to realise truly multivalent aluminium ion batteries based on organic active materials, by tuning the relative stability of discharged states with carrier ions of different valence states.
Adamczak D, Perinot A, Komber H, et al., 2021, Influence of synthetic pathway, molecular weight and side chains on properties of indacenodithiophene-benzothiadiazole copolymers made by direct arylation polycondensation, JOURNAL OF MATERIALS CHEMISTRY C, Vol: 9, Pages: 4597-4606, ISSN: 2050-7526
Paterson AF, Li R, Markina A, et al., 2021, N-Doping improves charge transport and morphology in the organic non-fullerene acceptor O-IDTBR dagger, JOURNAL OF MATERIALS CHEMISTRY C, Vol: 9, Pages: 4486-4495, ISSN: 2050-7526
Kafourou P, Park B, Luke J, et al., 2021, One‐step sixfold cyanation of benzothiadiazole acceptor units for air‐stable high‐performance n‐type organic field‐effect transistors, Angewandte Chemie, Vol: 133, Pages: 6035-6042, ISSN: 0044-8249
Reported here is a new high electron affinity acceptor end group for organic semiconductors, 2,1,3‐benzothiadiazole‐4,5,6‐tricarbonitrile (TCNBT). An n‐type organic semiconductor with an indacenodithiophene (IDT) core and TCNBT end groups was synthesized by a sixfold nucleophilic substitution with cyanide on a fluorinated precursor, itself prepared by a direct arylation approach. This one‐step chemical modification significantly impacted the molecular properties: the fluorinated precursor, TFBT IDT, a poor ambipolar semiconductor, was converted into TCNBT IDT, a good n‐type semiconductor. The electron‐deficient end group TCNBT dramatically decreased the energy of the highest occupied and lowest unoccupied molecular orbitals (HOMO/LUMO) compared to the fluorinated analogue and improved the molecular orientation when utilized in n‐type organic field‐effect transistors (OFETs). Solution‐processed OFETs based on TCNBT IDT exhibited a charge‐carrier mobility of up to μe≈0.15 cm2 V−1 s−1 with excellent ambient stability for 100 hours, highlighting the benefits of the cyanated end group and the synthetic approach.
Heeney M, Kafourou P, Park B, et al., 2021, One-step six-fold cyanation of benzothiadiazole acceptor Units for air-stable high-performance n-type organic field-effect transistors, Angewandte Chemie International Edition, Vol: 60, Pages: 5970-5977, ISSN: 1433-7851
We report a new high electron affinity acceptor end group for organic semiconductors, 2,1,3-benzothiadiazole-4,5,6-tricarbonitrile (TCNBT). An n-type organic semiconductor with an indacenodithiophene (IDT) core and TCNBT end groups was synthesized by a six-fold nucleophilic substitution with cyanides on a fluorinated precursor, itself prepared by a direct arylation approach. This one-step chemical modification was found to significantly impact the molecular properties: the fluorinated precursor, TFBT IDT, a poor ambipolar semiconductor, was converted into TCNBT IDT, a good n-type semiconductor. The highly electron-deficient end group TCNBT dramatically decreased the energy of the highest occupied and lowest unoccupied molecular orbitals (HOMO/LUMO) compared to the fluorinated analogue and improved the molecular orientation when utilized in n-type organic field-effect transistors (OFETs). Solution-processed OFETs based on TCNBT IDT exhibited a charge carrier mobility of up to µ e ≈ 0.15 cm 2 V -1 s -1 with excellent ambient stability for 100 hours, highlighting the benefits of the cyanated end group and the synthetic approach.
Hodsden T, Thorley KJ, Basu A, et al., 2021, The influence of alkyl group regiochemistry and backbone fluorination on the packing and transistor performance of N-cyanoimine functionalised indacenodithiophenes, Materials Advances, Vol: 2, Pages: 1706-1714
The synthesis of two novel n-type molecular organic semiconductors based on a fluorinated indacenodithiophene core in combination with an electron withdrawing N-cyanoimine group is reported, and the influence of the regiochemistry of the solubilizing sidechain is investigated. The N-cyanoimine is confirmed to be a strongly electron accepting group, which in combination with the core fluorination resulted in high electron affinities for both materials. Single crystal analysis demonstrated that whilst both materials arrange in ordered slipped stacks with close π–π stacking distances (∼3.40 Å), significant differences in electron transfer integrals for the two regioisomers were observed, relating to differences in relative molecular displacement along the π-stacking direction. Organic thin-film transistors fabricated via blade-coating displayed electron mobility up to 0.13 cm2 V−1 s−1 for the isomer with the larger transfer integral.
Rodriguez-Martinez X, Pascual-San-Jose E, Fei Z, et al., 2021, Predicting the photocurrent-composition dependence in organic solar cells, ENERGY & ENVIRONMENTAL SCIENCE, Vol: 14, Pages: 986-994, ISSN: 1754-5692
Marsh AV, Little M, Cheetham NJ, et al., 2020, Highly Deformed o-Carborane Functionalised Non-linear Polycyclic Aromatics with Exceptionally Long C-C Bonds, CHEMISTRY-A EUROPEAN JOURNAL, Vol: 27, Pages: 1970-1975, ISSN: 0947-6539
Lin Y, Nugraha MI, Firdaus Y, et al., 2020, A Simple n-Dopant Derived from Diquat Boosts the Efficiency of Organic Solar Cells to 18.3%, ACS ENERGY LETTERS, Vol: 5, Pages: 3663-3671, ISSN: 2380-8195
Basu A, Niazi MR, Scaccabarozzi AD, et al., 2020, Impact of p-type doping on charge transport in blade-coated small-molecule:polymer blend transistors, JOURNAL OF MATERIALS CHEMISTRY C, Vol: 8, Pages: 15368-15376, ISSN: 2050-7526
He Q, Eisner FD, Pearce D, et al., 2020, Ring fusion in tetrathienylethene cored perylene diimide tetramers affords acceptors with strong and broad absorption in the near-UV to visible region, Journal of Materials Chemistry C, Vol: 8, Pages: 17237-17244, ISSN: 2050-7526
In this work, we designed and synthesized two novel perylene diimide (PDI) tetramers based on a tetrathienylethene core, named TTE-PDI4 and FTTE-PDI4, and investigated their application as non-fullerene acceptors for organic photovoltaics. The free rotation of PDIs and adjacent thiophene units renders TTE-PDI4 with a highly twisted molecular geometry. The ring fusion of TTE-PDI4 yields FTTE-PDI4, a more rigid molecule with increased intramolecular stacking. Interestingly, TTE-PDI4 and FTTE-PDI4 possess similar energy levels but very different UV-Vis absorptions, with the latter showing strong broad-band absorption with multiple sharp peaks in the 300–600 nm region. Through time-dependent density functional theory (TD-DFT) calculations, we show that this broad absorption spectrum in FTTE-PDI4 arises from the combination of multiple bright transitions in the visible region with a strong vibronic progression, tentatively assigned to the dominant C[double bond, length as m-dash]C stretching mode. TTE-PDI4, despite having a lower energy absorption onset, shows weaker absorption at long wavelengths. Due to its higher absorption as well as its increased rigidity, FTTE-PDI4 shows a higher photocurrent and hence a higher power conversion efficiency (PCE), of 6.6%, when blended with the polymer donor PFBDB-T than TTE-PDI4 based blends (PCE of 3.8%). The greater rigidity of FTTE-PDI4 is likely to contribute to the good fill factor of the blend devices. Potential for further improvement through reducing voltage losses is identified.
Cong S, Creamer A, Fei Z, et al., 2020, Tunable control of the hydrophilicity and wettability of conjugated polymers by a postpolymerization modification approach., Macromolecular Bioscience, Vol: 20, Pages: 1-8, ISSN: 1616-5187
A facile method to prepare hydrophilic polymers by a postpolymerization nucleophillic aromatic substitution reaction of fluoride on an emissive conjugated polymer (CP) backbone is reported. Quantitative functionalization by a series of monofunctionalized ethylene glycol oligomers, from dimer to hexamer, as well as with high molecular weight polyethylene glycol is demonstrated. The length of the ethylene glycol sidechains is shown to have a direct impact on the surface wettability of the polymer, as well as its solubility in polar solvents. However, the energetics and band gap of the CPs remain essentially constant. This method therefore allows an easy way to modulate the wettability and solubility of CP materials for a diverse series of applications.
Tang Y, Bjuggren JM, Fei Z, et al., 2020, Origin of Open-Circuit Voltage Turnover in Organic Solar Cells at Low Temperature, SOLAR RRL, Vol: 4, ISSN: 2367-198X
Scaccabarozzi AD, Scuratti F, Barker AJ, et al., 2020, Understanding charge transport in high-mobilityp-doped multicomponent blend organic transistors, Advanced Electronic Materials, Pages: 1-9, ISSN: 2199-160X
The use of ternary systems comprising polymers, small molecules, and molecular dopants represents a promising approach for the development of high‐mobility, solution‐processed organic transistors. However, the current understanding of the charge transport in these complex systems, and particularly the role of molecular doping, is rather limited. Here, the role of the individual components in enhancing hole transport in the best‐performing ternary blend systems comprising the small molecule 2,7‐dioctylbenzothieno[3,2‐b]benzothiophene (C8‐BTBT), the conjugated polymer indacenodithiophene‐alt‐benzothiadiazole (C16IDT‐BT), and the molecular p‐type dopant (C60F48) is investigated. Temperature‐dependent charge transport measurements reveal different charge transport regimes depending on the blend composition, crossing from a thermally activated to a band‐like behavior. Using the charge‐modulation spectroscopy technique, it is shown that in the case of the pristine blend, holes relax onto the conjugated polymer phase where shallow traps dominate carrier transport. Addition of a small amount of C60F48 deactivates those shallow traps allowing for a higher degree of hole delocalization within the highly crystalline C8‐BTBT domains located on the upper surface of the blend film. Such synergistic effect of a highly ordered C8‐BTBT phase, a polymer bridging grain boundaries, and p‐doping results in the exceptionally high hole mobilities and band‐like transport observed in this blend system.
Wang S, Shaw J, Han Y, et al., 2020, Multibranched aliphatic side chains for π-conjugated polymers with a high density of ‘unshielded’ aromatics, Chemical Communications, Vol: 56, Pages: 12138-12141, ISSN: 1359-7345
Strongly solubilising multibranched aliphatic side chains for π-conjugated polymers are reported, enabling soluble polymers with a high density of unsubstituted, ‘unshielded’ aromatics.
Zhang D, Heeney M, 2020, Organic Donor-Acceptor Systems, ASIAN JOURNAL OF ORGANIC CHEMISTRY, Vol: 9, Pages: 1251-1251, ISSN: 2193-5807
Green JP, Dai H, Anies F, et al., 2020, Functional 4H-Dithieno[3,2-b:2 ',3 '-d]pyrrole Derivatives in Base-Dopable Conjugated Polymers and Oligomers, MACROMOLECULES, Vol: 53, Pages: 6649-6655, ISSN: 0024-9297
Anies F, Wang S, Hodsden T, et al., 2020, A Structurally Simple but High-Performing Donor-Acceptor Polymer for Field-Effect Transistor Applications, ADVANCED ELECTRONIC MATERIALS, Vol: 6, ISSN: 2199-160X
Eder S, Yoo D-J, Nogala W, et al., 2020, Switching between local and global aromaticity in a conjugated macrocycle for high-performance organic sodium-ion battery anodes, Angewandte Chemie International Edition, Vol: 59, Pages: 12958-12964, ISSN: 1433-7851
Aromatic organic compounds can be used as electrode materials in rechargeable batteries and are expected to advance the development of both anode and cathode materials for sodium-ion batteries (SIBs). However, most aromatic organic compounds assessed as anode materials in SIBs to date exhibit significant degradation issues under fast-charge/discharge conditions and unsatisfying long-term cycling performance. Now, a molecular design concept is presented for improving the stability of organic compounds for battery electrodes. The molecular design of the investigated compound, [22.214.171.124]paracyclophane-1,9,17,25-tetraene (PCT), can stabilize the neutral state by local aromaticity and the doubly reduced state by global aromaticity, resulting in an anode material with extraordinarily stable cycling performance and outstanding performance under fast-charge/discharge conditions, demonstrating an exciting new path for the development of electrode materials for SIBs and other types of batteries.
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