Cross-Linkable Fluorene-Diphenylamine Derivatives for Electrochromic Applications

A Holistic Review of C = C Crosslinkable Conjugated Molecules in Solution-Processed Organic Electronics: Insights into Stability, Processibility, and Mechanical Properties

Solution-processable organic conjugated molecules (OCMs) consist of a series of aromatic units linked by σ-bonds, which present a relatively freedom intramolecular motion and intermolecular re-arrangement under external stimulation. The cross-linked strategy provides an effective platform to obtain OCMs network, which allows for outstanding optoelectronic, excellent physicochemical properties, and substantial improvement in device fabrication. An unsaturated double carbon-carbon bond (C = C) is universal segment to construct crosslinkable OCMs. In this review, the authors will set C = C cross-linkable units as an example to summarize the development of cross-linkable OCMs for solution-processable optoelectronic applications. First, this review provides a comprehensive overview of the distinctive chemical, physical, and optoelectronic properties arising from the cross-linking strategies employed in OCMs. Second, the methods for probing the C = C cross-linking reaction are also emphasized based on the perturbations of chemical structure and physicochemical property. Third, a series of model C = C cross-linkable units, including styrene, trifluoroethylene, and unsaturated acid ester, are further discussed to design and prepare novel OCMs. Furthermore, a concise overview of the optoelectronic applications associated with this approach is presented, including light-emitting diodes (LEDs), solar cells (SCs), and field-effect transistors (FETs). Lastly, the authors offer a concluding perspective and outlook for the improvement of OCMs and their optoelectronic application via the cross-linking strategy.

Thermally cross-linkable fluorene-based hole transporting materials: synthesis, characterization, and application in perovskite solar cells

Perovskite solar cells are among the most promising photovoltaic technologies in academia and have the potential to become commercially available in the near future. However, there are still a few unresolved issues regarding device lifetime and fabrication cost of perovskite solar cells in order to be competitive with existing technologies. Herein, we report small organic molecules with introduced vinyl groups as hole transporting materials, which are capable of undergoing thermal polymerization, forming solvent-resistant 3D networks. Novel compounds have been synthesized from relatively inexpensive starting materials and their purification is less time-consuming when compared to polymers; therefore this type of hole transporter can be a promising alternative to lower the manufacturing cost of perovskite solar cells.

Liquid/Liquid Interfacial Suzuki Polymerization Prepared Novel Triphenylamine-Based Conjugated Polymer Films with Excellent Electrochromic Properties

Preparing conjugated polymer films via interfacial Suzuki polymerization is a promising method for obtaining desirable electrochromic materials with desired structures. Here, a series of aryl boronic esters and triphenylamine-based aryl bromides were applied as precursors, and several polymer films were finally obtained via the liquid/liquid interfacial Suzuki polymerization reaction under mild conditions. FT-IR, UV, and Raman as well as electrochemistry, SEM, and EDS results all provide strong evidence for the formation of the desired polymer structures. Among them, the TPA-Wu (containing triphenylamine and alkyl-fluorene) film exhibits the best film-forming quality. Besides, these polymer films were applied in electrochromic applications. The results show that electrochromic properties can be affected by the quality of film formation. It is worth mentioning that the TPA-Wu film could achieve excellent electrochromic properties with reversible multicolor changes from transparent yellow to orange-red to blue-green under varying potentials. Compared to other triphenylamine-based electrochromic materials, the TPA-Wu film possessed the most desirable coloring efficiency, higher optical contrast, and shorter switching time. This work provides an existing general approach of liquid/liquid interfacial Suzuki polymerization for constructing conjugated polymer films toward electrochromic applications.

Electropolymerization of D–A–D type monomers consisting of triphenylamine and substituted quinoxaline moieties for electrochromic devices

We reported three D–A–D type monomers consisting of triphenylamine and substituted quinoxaline moieties, and their electrochemical polymerization for electrochromic devices.

Bioinspired Color-Changeable Organogel Tactile Sensor with Excellent Overall Performance

Inspired by chameleons' structural color regulation capability, a simple, but effective, swelling method is proposed for the first time to prepare an ionic polyacrylamide (PAAm) organogel for simultaneous tactile sensing and interactive color changing. The PAAm organogel obtained by swelling the PAAm scaffold in the dimethyl sulfoxide solution of organic electrochromic material (OECM) shows an extremely large stretchability with an elongation of 1600%, a supersoftness with a compressive modulus of 7.2 kPa, an excellent transmittance up to 90%, and a very fast response time of 0.5 s combined with the characteristic of interactive color changing. The PAAm organogel also suggests a universal design ability to tailor coloration spectra for tactile sensors via simply changing the type and content of OECM. The tactile sensor based on a PAAm organogel is capable of serving as a wearable device for precisely tracing human body motion performance and directly visualizing the stress distribution via interactive color changing capability. It is demonstrated that the swelling method proposed here is a simple and practical strategy to prepare ionic organogels with both piezo-resistive and electrochromic effects.

New porphyrin dendrimers with fluorenyl-based connectors: a simple way to improving the optical properties over dendrimers featuring 1,3,5-phenylene connectors

Dendrimers with new fluorenyl-based connectors have been synthesized and characterized. Their detailed luminescence properties and selected photophysical properties are discussed in the frame of two-photon-induced theranostics.

Visible-to-NIR Electrochromic Device Prepared from a Thermally Polymerizable Electroactive Organic Monomer

A monomer (1) consisting of a benzothiadiazole core flanked by two triphenylamines and two styrene pendant moieties was prepared. The monomer was fluorescent with its emission spanning 145 nm in the visible, contingent on the organic solvent used for the measurement. In addition to its positive solvatochromism, the absolute fluorescence quantum yield (Φ_fl) was consistently >20% with values >80% being measured in hexane, toluene, diethyl ether, and toluene. 1 could be reversibly oxidized with an oxidation potential of 880 mV vs SCE. The monomer could be immobilized on ITO-coated glass substrates. The resulting 425 nm thick immobilized film (poly-1) was 15% thinner than the monomer coating deposited by spray- and spin-coating. The electroactive film did not delaminate from the electrode upon either washing or cycling electrochemically between its oxidized and neutral states. Its absorption at 460 nm bleached upon electrochemical oxidation with the formation of a strong absorption at 880 nm and in the NIR, similar to 1. The perceived reversible color change with applied potential switched between yellow and gray. The fluorescence intensity of poly-1 could be switched with applied potentials. A passive transmissive device prepared from poly-1 was both electrochromic and fluorochromic, exhibiting reversible color change and fluorescence quenching.

Orthogonal electronic coupling in multicentre arylamine mixed-valence compounds based on a dibenzofulvene–thiophene conjugated bridge

Novel H-shaped tetrarylamine mixed valence compounds showing orthogonal electronic coupling generate voltage-dependent electro-optical modulation in the near infrared region.

Selenium-Containing Fused Bicyclic Heterocycle Diselenolodiselenole: Field Effect Transistor Study and Structure-Property Relationship

The first application of the diselenolodiselenole (C4Se4) heterocycle as an active organic field effect transistor materials is demonstrated here. C4Se4 derivatives (2a-2d) were obtained by using a newly developed straightforward diselenocyclization protocol, which includes the reaction of diynes with selenium powder at elevated temperature. C4Se4 derivatives exhibit strong donor characteristics and planar structure (except 2d). The atomic force microscopic analysis and thin-film X-ray diffraction pattern of compounds 2a-2d indicated the formation of distinct crystalline films that contain large domains. A scanning electron microscopy study of compound 2b showed development of symmetrical grains with an average diameter of 150 nm. Interestingly, 2b exhibited superior hole mobility, approaching 0.027 cm(2) V(-1) s(-1) with a transconductance of 9.2 μS. This study correlate the effect of π-stacking, Se···Se intermolecular interaction, and planarity with the charge transport properties and performance in the field effect transistor devices. We have shown that the planarity in C4Se4 derivatives was achieved by varying the end groups attached to the C4Se4 core. In turn, optoelectronic properties can also be tuned for all these derivatives by end-group variation.