Copolymers possessing dithienothiophene and boron for optoelectronic applications

Electrochemical copolymerization of 3,4-ethylenedioxythiophene and dithienothiophene: influence of feed ratio on electrical, optical and electrochromic properties

Designing a copolymer is an efficient and alternative method to generate new chemical and physical properties compared to parent homopolymers without complex synthesis and structural modification. We herein report the electrochemical deposition of copolymer using two monomers 3,4-ethylenedioxythiophene (EDOT) and dithieno[3,2-b:2',3'-d]thiophene (DTT). Three different copolymers P[EDOT-co-DTT] were synthesized by using different feed ratios of monomers (EDOT and DTT molar ratios in solution are 2 : 1, 1 : 1 and 1 : 2) in acetonitrile containing 0.1 M tetrabutylammonium perchlorate (TBAClO4) as a supporting electrolyte. Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and UV-vis-NIR spectroscopy were employed to characterize the obtained copolymers. Energy dispersive X-ray spectroscopy (EDX) analysis was used to estimate the composition of EDOT and DTT units in copolymers. The electrochemical and morphological properties were analyzed using cyclic voltammetry (CV) and field emission scanning electron microscopy (FESEM). In situ spectroelectrochemistry and electrochromic studies were performed to investigate the optical and switching properties of the resultant copolymers. The homopolymers poly(3,4-ethylenedioxythiophene) (PEDOT) and polydithieno[3,2-b:2',3'-d]thiophene (PDTT) were also prepared using similar electrochemical conditions and made comparisons where applicable. Computational calculations were done to understand the structure and energy levels of these polymers. It was found that these copolymers P[EDOT-co-DTT] show new properties as compared to homopolymers PEDOT and PDTT for organic electronic applications. Interesting to note that the resultant copolymers display the property of tunable electrochromism with improved transmittance and redox color change between the neutral and oxidized states.

Dithieno[3,2-b:2',3'-d]thiophene (DTT): an emerging heterocyclic building block for future organic electronic materials & functional supramolecular chemistry

Heterocyclic compounds being potent biochemical materials are ubiquitous molecules in our life. Amongst, the five membered aromatic ring systems, thiophene has emerged as a remarkable entity in organic electronics owing to its (i) high resonance energy, (ii) more electrophilic reactivity than benzene, (iii) high π-electron density, (iv) planar structure and, (v) presence of vacant d-orbital in addition to the presence of loosely bind lone-pairs of electrons on sulfur atoms. In recent past, thiophene-fused molecule namely, dithienothiophene (DTT) has attracted a tremendous attention of the researchers worldwide due to their potential applicability in organic electronics such as in solar cells, electrochromic devices (ECDs), organic field effect transistors (OFETs), organic limiting diodes (OLEDs), fluorescent probes, redox switching and so forth because of their (i) higher charge mobility, (ii) extended π-conjugation, and (iii) better tuning of band gaps, etc. In this particular review article, we envisioned to report the recent advancements made on the DTT-based architectures not only because of the potential applicability of this valuable scaffold in organic electronic but also to motivate the young researchers worldwide to look for the challenging opportunities related to this privileged building block in both material sciences and functional supramolecular chemistry.

Introducing a new 7-ring fused diindenone-dithieno[3,2-b:2',3'-d]thiophene unit as a promising component for organic semiconductor materials

A novel π-conjugated molecule, EtH-T-DI-DTT is reported, which is fused, rigid, and planar, featuring the electron-rich dithieno[3,2-b:2',3'-d]thiophene (DTT) unit in the core of the structure. Adjacent to the electron-donating DTT core, there are indenone units with electron-withdrawing keto groups. To enable solubility in common organic solvents, the fused system is flanked by ethylhexylthiophene groups. The material is a dark, amorphous solid with an onset of absorption at 638 nm in CH2Cl2 solution, which corresponds to an optical gap of 1.94 eV. In films, the absorption onset wavelength is at 701 nm, which corresponds to 1.77 eV. An ionisation energy of 5.5 eV and an electron affinity of 3.3 eV were estimated by cyclic voltammetry measurements. We have applied this new molecule in organic field effect transistors. The material exhibited a p-type mobility up to 1.33 × 10-4 cm2 V-1 s-1.

Triarylborane-Based Materials for OLED Applications

Multidisciplinary research on organic fluorescent molecules has been attracting great interest owing to their potential applications in biomedical and material sciences. In recent years, electron deficient systems have been increasingly incorporated into fluorescent materials. Triarylboranes with the empty p orbital of their boron centres are electron deficient and can be used as strong electron acceptors in conjugated organic fluorescent materials. Moreover, their applications in optoelectronic devices, energy harvesting materials and anion sensing, due to their natural Lewis acidity and remarkable solid-state fluorescence properties, have also been investigated. Furthermore, fluorescent triarylborane-based materials have been commonly utilized as emitters and electron transporters in organic light emitting diode (OLED) applications. In this review, triarylborane-based small molecules and polymers will be surveyed, covering their structure-property relationships, intramolecular charge transfer properties and solid-state fluorescence quantum yields as functional emissive materials in OLEDs. Also, the importance of the boron atom in triarylborane compounds is emphasized to address the key issues of both fluorescent emitters and their host materials for the construction of high-performance OLEDs.

Organoboron copolymers containing thienothiophene and selenophenothiophene analogues: optical, electrochemical and fluoride sensing properties

Conjugated D–A copolymers of SeT/TT and mesitylboron were synthesized. Large Stokes shifts of 96–166 nm and solution quantum yields of 5–18% were recorded. High fluoride sensing property was observed for the polymer having cross-conjugated-TT units.