The electronics era is flourishing and morphing itself into Internet of Everything, IoE. At the same time, questions arise on the issue of electronic materials employed: especially their natural ...availability and low-cost fabrication, their functional stability in devices, and finally their desired biodegradation at the end of their life cycle. Hydrogen bonded pigments and natural dyes like indigo, anthraquinone and acridone are not only biodegradable and of bio-origin but also have functionality robustness and offer versatility in designing electronics and sensors components. With this Perspective, we intend to coalesce all the scattered reports on the above-mentioned classes of hydrogen bonded semiconductors, spanning across several disciplines and many active research groups. The article will comprise both published and unpublished results, on stability during aging, upon electrical, chemical and thermal stress, and will finish with an outlook section related to biological degradation and biological stability of selected hydrogen bonded molecules employed as semiconductors in organic electronic devices. We demonstrate that when the purity, the long-range order and the strength of chemical bonds, are considered, then the Hydrogen bonded organic semiconductors are the privileged class of materials having the potential to compete with inorganic semiconductors. As an experimental historical study of stability, we fabricated and characterized organic transistors from a material batch synthesized in 1932 and compared the results to a fresh material batch.
Robust organic thin-film transistors (OTFTs) with high temperature stability allow device integration with mass production methods like thermoforming and injection molding, and enable operation in ...extreme environment applications. Herein we elaborate a series of materials to make suitable gate dielectric and active semiconductor layers for high temperature stable OTFTs. We employ an anodized aluminum oxide layer passivated with cross-linked low-density polyethylene (LD-PE) to form a temperature-stable gate capacitor. As the semiconductor, we use quinacridone, an industrial organic colorant pigment produced on a mass scale. Evaporated MoOx/Ag source and drain electrodes complete the devices. Here we evaluate the performance of the OTFTs heating them in air from 100 °C in 25 °C increments up to 225 °C, holding each temperature for a period of 30 minutes. We find large differences in stability between quinacridone and its dimethylated derivative, with the former showing the best performance with only a factor of 2 decline in mobility after heating at 225 °C, and unaffected on/off ratio and threshold voltage. The approach presented here shows how industriallys calable fabrication of thermally robust OTFTs can be rationalized.
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•Quinacridone pigments as an active component in organic thin film transistors.•Operational air-stability, remarkable temperature resistance and high charge carrier mobility.•Thermal stability up to 225 °C in air without significant degradation.•Quinacridone thin film transistors are candidates for thermoforming and injection molding applications.
Injection-charge extraction by linearly increasing voltage in metal-insulator-semiconductor structures (MIS-CELIV) is applied for the hole mobility measurement of ...N,N’-Bis(naphthalen-1-yl)-N,N’-bis(phenyl)-benzidine (NPB), which is a standard hole-transporting material for organic light-emitting diodes. Ideal transient currents in agreement with the theory are observed in the NPB film due to its amorphous and homogenous structure, which is regarded as a continuous dielectric. This ideal response enables us to discuss the validity of the MIS-CELIV mobility by comparing its absolute value with that of the conventional space-charge-limited current method. In addition, to establish an experimental guideline for precise measurements, the effect of the voltage drop on the insulator is investigated.
Hydrogen‐bonded pigments are remarkably stable high‐crystal lattice energy organic solids. Here a lesser‐known family of compounds, the epindolidiones, which demonstrates electronic transport with ...extraordinary stability, even in highly demanding aqueous environments, is reported. Hole mobilities in the range 0.05–1 cm2 V–1 s–1 can be achieved, with lower electron mobilities of up to 0.1 cm2 V–1 s–1. To help understand charge transport in epindolidiones, X‐ray diffraction is used to solve the crystal structure of 2,8‐difluoroepindolidione and 2,8‐dichloroepindolidione. Both derivatives crystallize with a linear‐chain H‐bonding lattice featuring two‐dimensional π–π stacking. Powder diffraction indicates that the unsubstituted epindolidione has very similar crystallinity. All types of epindolidiones measured here display strong low‐energy optical emission originating from excimeric states, which coexists with higher‐energy fluorescence. This can be exploited in light‐emitting diodes, which show the same hybrid singlet and low‐energy excimer electroluminescence. Low‐voltage FETs are fabricated with epindolidione, which operate reliably under repeated cyclic tests in different ionic solutions within the pH range 3–10 without degradation. Finally, in order to overcome the insolubility of epindolidiones in organic solvents, a chemical procedure is devised to allow solution‐processing via the introduction of suitable thermolabile solubilizing groups. This work shows the versatile potential of epindolidione pigments for electronics applications.
Epindolidiones are H‐bonded organic pigment semiconductors with excellent operational stability, including in aqueous media. Their crystal structure, electrochemical properties, and photophysics, which are dominated by excimeric effects, are reported. Transistor and light‐emitting devices are demonstrated. Routes for solution processing of epindolidiones using transient solubilizing groups are explored.
Combining the unique properties of peptides as versatile tools for nano- and biotechnology with lead halide perovskite nanoparticles can bring exceptional opportunities for the development of ...optoelectronics, photonics, and bioelectronics. As a first step towards this challenge sub 10 nm methylammonium lead bromide perovskite colloidal nanoparticles have been synthetizes using commercial cyclic peptide Cyclo(RGDFK), containing 5 amino acids, as a surface stabilizer. Perovskite nanoparticles passivated with Cyclo(RGDFK) possess charge transfer from the perovskite core to the peptide shell, resulting in lower photoluminescence quantum yields, which however opens a path for the application where charge transfer is favorable.
Millions of people worldwide are diagnosed with retinal dystrophies such as retinitis pigmentosa and age-related macular degeneration. A retinal prosthesis using organic photovoltaic (OPV) ...semiconductors is a promising therapeutic device to restore vision to patients at the late onset of the disease. However, an appropriate cytotoxicity approach has to be employed on the OPV materials before using them as retinal implants. In this study, we followed ISO standards to assess the cytotoxicity of D18, Y6, PFN-Br and PDIN individually, and as mixtures of D18/Y6, D18/Y6/PFN-Br and D18/Y6/PDIN. These materials were proven for their high performance as organic solar cells. Human RPE cells were put in direct and indirect contact with these materials to analyze their cytotoxicity by the MTT assay, apoptosis by flow cytometry, and measurements of cell morphology and proliferation by immunofluorescence. We also assessed electrophysiological recordings on mouse retinal explants via microelectrode arrays (MEAs) coated with D18/Y6. In contrast to PFN-Br and PDIN, all in vitro experiments show no cytotoxicity of D18 and Y6 alone or as a D18/Y6 mixture. We conclude that D18/Y6 is safe to be subsequently investigated as a retinal prosthesis.
A series of novel soluble nature-inspired flavin derivatives substituted with short butyl and bulky ethyl-adamantyl alkyl groups was prepared via simple and straightforward synthetic approach with ...moderate to good yields. The comprehensive characterization of the materials, to assess their application potential, has demonstrated that the modification of the conjugated flavin core enables delicate tuning of the absorption and emission properties, optical bandgap, frontier molecular orbital energies, melting points, and thermal stability. Moreover, the thin films prepared thereof exhibit smooth and homogeneous morphology with generally high stability over time.
Conjugated donor-acceptor molecules with intramolecular charge transfer absorption are employed for single-component organic solar cells. Among the five types of donor-acceptor molecules, the strong ...push-pull structure of DTDCPB resulted in solar cells with high
, an internal quantum efficiency exceeding 20%, and high
exceeding 1 V with little photon energy loss around 0.7 eV. The exciton binding energy (EBE), which is a key factor in enhancing the photocurrent in the single-component device, was determined by quantum chemical calculation. The relationship between the photoexcited state and the device performance suggests that the strong internal charge transfer is effective for reducing the EBE. Furthermore, molecular packing in the film is shown to influence photogeneration in the film bulk.
We set out to demonstrate the development of a highly conductive polymer based on poly-(3,4-ethylenedithia thiophene) (PEDTT), PEDOTs structural analogue historically notorious for structural ...disorder and limited conductivities. The caveat therein was previously described to lie in intra-molecular repulsions. We demonstrate how a tremendous >2600-fold improvement in conductivity and metallic features, such as magnetoconductivity can be achieved. This is achieved through a careful choice of the counter-ion (sulphate) and the use of oxidative chemical vapour deposition (oCVD). It is shown that high structural order on the molecular level was established and the formation of crystallites tens of nanometres in size was achieved. We infer that the sulphate ions therein intercalate between the polymer chains, thus forming densely packed crystals of planar molecules with extended π-systems. Consequently, room-temperature conductivities of above 1000 S cm
−1
are achieved, challenging those of conventional PEDOT:PSS. The material is in the critical regime of the metal-insulator transition.
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