Spray-processable thiazolothiazole-based copolymers with altered donor groups and their electrochromic properties

Correlating structure and photophysical properties in thiazolo[5,4-d]thiazole crystal derivatives for use in solid-state photonic and fluorescence-based optical devices

There is a growing demand for new fluorescent small molecule dyes for solid state applications in the photonics and optoelectronics industry. Thiazolo[5,4-d]thiazole (TTz) is an organic heterocycle moiety which has previously shown remarkable properties as a conjugated polymer and in solution-based studies. For TTz-based small molecules to be incorporated in solid-state fluorescence-based optical devices, a thorough elucidation of their structure-photophysical properties needs to be established. Herein, we have studied four TTz-based materials functionalized with alkyl appendages of varying carbon chain lengths. We report the single crystal structures of the TTz derivatives, three of which were previously unknown. The packing modes of the crystals reveal that molecular arrangements are largely governed by a chorus of synergistic intermolecular non-covalent interactions. Three crystals packed in herringbone mode and one crystal packed in slipped stacks proving that alkyl appendages modulate structural organization in TTz-based materials. Steady state and time-resolved photophysical properties of these crystals were studied via diffuse-reflectance, micro-Raman, and photoluminescence spectroscopy. The crystals fluoresce from orange-red to blue spanning through the whole gamut of the visible spectrum. We have established that photophysical properties are a function of crystal packing in symmetrically substituted TTz-based materials. This correlation was then utilized to fabricate crystalline blends. We demonstrate, for the first time, that symmetrically substituted donor-acceptor-donor TTz-based materials can be used for phosphor-converted color-tuning and white-light emission. Given the cost effectiveness, ease of synthesis and now a structure-photophysics correlation, we present a compelling case for the adoption of TTz-based materials in solid-state photonic and fluorescence-based optical devices.

A deep look into the spray coating process in real-time-the crucial role of x-rays

Tailoring functional thin films and coating by rapid solvent-based processes is the basis for the fabrication of large scale high-end applications in nanotechnology. Due to solvent loss of the solution or dispersion inherent in the installation of functional thin films and multilayers the spraying and drying processes are strongly governed by non-equilibrium kinetics, often passing through transient states, until the final structure is installed. Therefore, the challenge is to observe the structural build-up during these coating processes in a spatially and time-resolved manner on multiple time and length scales, from the nanostructure to macroscopic length scales. During installation, the interaction of solid-fluid interfaces and between the different layers, the flow and evaporation themselves determine the structure of the coating. Advanced x-ray scattering methods open a powerful pathway for observing the involved processes in situ, from the spray to the coating, and allow for gaining deep insight in the nanostructuring processes. This review first provides an overview over these rapidly evolving methods, with main focus on functional coatings, organic photovoltaics and organic electronics. Secondly the role and decisive advantage of x-rays is outlined. Thirdly, focusing on spray deposition as a rapidly emerging method, recent advances in investigations of spray deposition of functional materials and devices via advanced x-ray scattering methods are presented.

Synthesis of carbazole-based copolymers containing carbazole-thiazolo[5,4-d]thiazole groups with different dopants and their fluorescence and electrical conductivity applications

The electrical conductivity of poly(carbazole-thiazolo[5,4-d]thiazole) was measured with the introduction of five different dopants (HCl, Fe(iii), Cu(ii), H₃BO₃, and I₂) into its framework through protonation of a nitrogen atom or complex formation.

Highly Regiosymmetric Homopolymer Based on Dioxythiophene for Realizing Water-Processable Blue-to-Transmissive Electrochrome

A highly regiosymmetric homopolymer based on a diethyl malonate derivatized 3,4-propylenedioxythiophene (ProDOT) monomer was synthesized through FeCl3 oxidative polymerization and postpolymerization functionalization to realize a water-processable blue-to-transmissive switching electrochromic polymer (WPECP-blue). As an electrochromic material, the polymer has a high electrochromic contrast ΔTmax=56% at 580 nm and a relatively fast switching speed t95=1.8 s, and shows only contrast loss of 11% (from 56% to 45%) at square wave potential step of 5 s over 11,000 switching cycles, making it a desirable candidate for electrochromic applications such as windows and displays.

The electronic, optical and magnetic consequences of delocalization in multifunctional donor–acceptor organic polymers

Redox reactions on electroactive donor–acceptor polymers can be used to tune their response to external magnetic and electrical stimuli.

Spray-processable red-to-transmissive electrochromic polymers towards fast switching time for display applications

The introduction of a thiophene unit in red-to-transmissive electrochromic polymers successfully improves the switching speed (t₉₅ = 1.6 s).

Low-band gap and fluorescent poly(triphenylamine-thiazolo[5,4-d]thiazole) copolymer dye

The synthesis, characterization and spectroscopy of a new fluorescent poly(triphenylamine-thiazolo[5,4-d]thiazole) dye with low band gap energy have been reported.

Photopatternable electrochromic materials from oxetane precursors

Conjugated thiophenoazomethine triads containing an acid sensitive oxetane group were prepared. The solution processable monomers were immobilized on glass and ITO coated glass substrates by photoacid induced cationic ring-opening polymerization (CROP) of the oxetane moiety. Photolithography using a photoacid generator and photosensitizer were used to pattern an electroactive polymer. Micro- and macroscale patterns ranging between 20 μm and 50 mm were possible with the electrochromic materials. The photopolymerized azomethine remained electroactive, and it could be repeatedly switched electrochemically between its neutral (mauve, λmax=535 nm) and oxidized (blue, λmax=585 nm) states without degradation. The electrochromic properties were evaluated in a simulated device where the colors were successfully cycled between blue (oxidized) and purple (neutral) states with applied biases of +0.6 V and -0.6 V vs Fc/Fc+ under ambient conditions without significant color fatigue or degradation.

Effects of different dopants on the band gap and electrical conductivity of the poly(phenylene-thiazolo[5,4-d]thiazole) copolymer

Band gap energy and electrical conductivity of poly(phenylene-thiazolo[5,4-d]thiazole) were compared for different dopants.