Design and synthesis of N-substituted perylene diimide based low band gap polymers for organic solar cell applications

Microscopic, Spectroscopic, and Electrochemical Characterization of Novel Semicrystalline Poly(3-hexylthiophene)-Based Dendritic Star Copolymer

In this study, electron-donating semicrystalline generation 1 poly(propylene thiophenoimine)-co-poly(3-hexylthiophene) star copolymer, G1PPT-co-P3HT was chemically prepared for the first time. Copolymerization was achieved with high molecular weight via facile green oxidative reaction. ¹H NMR analyses of the star copolymer demonstrated the presence of 84% regioregular (rr) head-to-tail (HT) P3HT, which accounts for the molecular ordering in some grain regions in the macromolecule’s morphology, as revealed by the high-resolution scanning electron microscopy (HRSEM) and Selected Area Electron Diffraction (SAED) images, and X-ray diffraction spectroscopy (XRD) measurements. The star copolymer also exhibited good absorption properties in the ultraviolet-visible (UV-Vis) and the near infrared (NIR) spectral regions, which give rise to an optical energy bandgap value as low as 1.43 eV. A HOMO energy level at −5.53 eV, which is below the air-oxidation threshold, was obtained by cyclic voltammetry (CV). Electrochemical impedance spectroscopy (EIS) ascertained the semiconducting properties of the macromolecule, which is characterized by a charge transfer resistance, R_ct, value of 3.57 kΩ and a Bode plot-phase angle value of 75°. The combination of the EIS properties of G1PPT-co-P3HT and its highly electron-donating capability in bulk heterojunction (BHJ) active layer containing a perylene derivative, as demonstrated by photoluminescence quenching coupled to the observed Förster Resonance charge transfer, suggests its suitability as an electron-donor material for optoelectronic and photovoltaic devices.

A "Rigid-Flexible" Approach for Processable Perylene Diimide-Based Polymers: Influence of the Specific Architecture on the Morphological, Dielectric, Optical, and Electronic Properties

Conjugation-break flexible spacers in-between π-conjugated segments were utilized herein toward processable perylene diimide (PDI)-based polymers. Aromatic-aliphatic PDI-based polymers were developed via the two-phase polyetherification of a phenol-difunctional PDI monomer and aliphatic dibromides. These polyethers showed excellent solubility and film-forming ability and deep lowest unoccupied molecular orbital (LUMO) levels (-4.0 to -3.85 eV), indicating the preservation of good electron-accepting character or characteristics, despite the non-conjugated segments. Their thermodynamic properties, local dynamics, and ionic conductivity demonstrate the suppression of PDI's inherent tendency for aggregation and crystallization, suggesting PDI-polyethers as versatile candidates for organic electronic applications. Their dynamics investigation using dielectric spectroscopy revealed weak dipole moments arising from the distortion of the planar perylene cores. Blends of the PDI-polyethers (as electron acceptors) with P3HT (as a potential electron donor component) showed UV-vis absorbances from 350 to 650 nm and a tendency of the PDI-polyethers to intertwine with rr-P3HT and restrain its high crystallization tendency.