RESUMEN
Side-chain engineering in molecular semiconductors provides a versatile toolbox for precisely manipulating the material's processability, crystallographic properties, as well as electronic and optoelectronic characteristics. This study explores the impact of integrating hydrophilic side chains, specifically oligoethylene glycol (OEG) units, into the molecular structure of the small molecule semiconductor, 2,7-bis(2(2-methoxy ethoxy)ethoxy) benzo[b]benzo[4,5] thieno[2,3-d] thiophene (OEG-BTBT). The investigation includes a comprehensive analysis of thin film morphology and crystallographic properties, along with the optimization of deposition parameters for improving the device performance. Despite the anticipated benefits, such as enhanced processability, our investigation into OEG-BTBT-based organic field-effect transistors (OFETs) reveals suboptimal performance marked by a low effective charge carrier mobility, a low on/off ratio, and a high threshold voltage. The study unveils bias stress effects and device degradation attributed to the high ionization energy of OEG-BTBT alongside the hydrophilic nature of the ethylene-glycol moieties, which lead to charge trapping at the dielectric interface. Our findings underscore the need for a meticulous balance between electronic properties and chemical functionalities in molecular semiconductors to achieve stable and efficient performance in organic electronic devices.
RESUMEN
Organic semiconductors are a family of pi-conjugated compounds used in many applications, such as displays, bioelectronics, and thermoelectrics. However, their susceptibility to processing-induced contamination is not well understood. Here, it is shown that many organic electronic devices reported so far may have been unintentionally contaminated, thus affecting their performance, water uptake, and thin film properties. Nuclear magnetic resonance spectroscopy is used to detect and quantify contaminants originating from the glovebox atmosphere and common laboratory consumables used during device fabrication. Importantly, this in-depth understanding of the sources of contamination allows the establishment of clean fabrication protocols, and the fabrication of organic field effect transistors (OFETs) with improved performance and stability. This study highlights the role of unintentional contaminants in organic electronic devices, and demonstrates that certain stringent processing conditions need to be met to avoid scientific misinterpretation, ensure device reproducibility, and facilitate performance stability. The experimental procedures and conditions used herein are typical of those used by many groups in the field of solution-processed organic semiconductors. Therefore, the insights gained into the effects of contamination are likely to be broadly applicable to studies, not just of OFETs, but also of other devices based on these materials.
RESUMEN
The development of systems capable of responding to environmental changes, such as humidity, requires the design and assembly of highly sensitive and efficiently transducing elements. Such a challenge can be mastered only by disentangling the role played by each component of the responsive system, thus ultimately achieving high performance by optimizing the synergistic contribution of all functional elements. Here, we designed and synthesized a novel [1]benzothieno[3,2-b][1]benzothiophene derivative equipped with hydrophilic oligoethylene glycol lateral chains (OEG-BTBT) that can electrically transduce subtle changes in ambient humidity with high current ratios (>104) at low voltages (2 V), reaching state-of-the-art performance. Multiscale structural, spectroscopical, and electrical characterizations were employed to elucidate the role of each device constituent, viz., the active material's BTBT core and OEG side chains, and the device interfaces. While the BTBT molecular core promotes the self-assembly of (semi)conducting crystalline films, its OEG side chains are prone to adsorb ambient moisture. These chains act as hotspots for hydrogen bonding with atmospheric water molecules that locally dissociate when a bias voltage is applied, resulting in a mixed electronic/protonic long-range conduction throughout the film. Due to the OEG-BTBT molecules' orientation with respect to the surface and structural defects within the film, water molecules can access the humidity-sensitive sites of the SiO2 substrate surface, whose hydrophilicity can be tuned for an improved device response. The synergistic chemical engineering of materials and interfaces is thus key for designing highly sensitive humidity-responsive electrical devices whose mechanism relies on the interplay of electron and proton transport.
RESUMEN
Electrochromic sensors offer multi-mode registration of analytical signal based on combination of electrochemical and optical techniques. This emerging direction of analytical chemistry is relatively new; therefore, it has very high potential for various applications in chemical and biochemical analysis. Properties of sensors based on various electrochromic materials such as polymers, polymer derivatives, polymer composites, metal oxides, metal oxide complexes, phthalocyanines, porphyrins, and dyes are critically overviewed, evaluated, and compared. The most promising directions in analytical application of electrochromic polymers are highlighted.
Asunto(s)
Complejos de Coordinación/análisis , Técnicas Electroquímicas , Metales/análisis , Óxidos/análisis , Polímeros/análisis , Colorantes/análisis , Indoles/análisis , Isoindoles , Porfirinas/análisisRESUMEN
An electrochromic material based on azobenzene and 3,4-ethylenedioxythiophene (EDOT) semiconducting layer was electrochemically deposited on an indium tin oxide coated glass electrode. Chemical synthesis of the azobenzene and EDOT-based chromophore (DAE) and electrochemical formation of its corresponding polymer (pDAE) are reported. The electrochromic properties of the synthesized polymer pDAE were investigated by electrochemical and spectroelectrochemical methods. pDAE exhibited an optical bandgap of 1.82â eV and three distinct colored states in its reduced, neutral, and oxidized forms. The pDAE polymer showed 44 % optical contrast at 710â nm between its reduced and oxidized states and a fast electrochromic switching time of 1.0â s. The frontier molecular orbitals, Raman shifts, and semiconducting properties of this electrochromic polymer were evaluated by density functional theory calculations. The optical absorption bands of the polymer charged states were assigned and investigated.