Synthesis and self-assembly of thiophene-based all-conjugated amphiphilic diblock copolymers with a narrow molecular weight distribution

A series of amphiphilic poly(3-hexylthiophene-b-3-(2-(2-{2-[2-(2-methoxy ethoxy)-ethoxy]-ethoxy}-ethyl))thiophene) (P(3HT-b-3EGT)) polymers was synthesized via a nickel-catalyzed quasi-living polymerization. Size exclusion chromatograms (SEC) revealed that the molecular weight distributions of the P3HT blocks in the block copolymers were comparable with those of the polystyrene standard (monodisperse). NMR spectra revealed that the P3HT and PEGT units in the block copolymers were well-defined and did not form compositionally mixed regions at the boundary between the blocks and the highly regioregular P3HT units. The correlations among the block ratio, the amphiphilicity, and the self-assembled nanostructures of the block copolymers in thin films and in solution were examined. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) studies revealed that the crystallinity of the BP93 composed of 93 mol % P3HT blocks was higher than the crystallinity of the P3HT alone due to the packing effects caused by repulsion among the hydrophobic hexyl and hydrophilic ethylene glycol oligomer side chains. A long relaxation time was required to observe the ordering among P3HT blocks in the BP26 composed of 26 mol % P3HT blocks, suggesting that self-assembly could occur if induced on the molecular level. We demonstrated that the molecular-level self-assembly of BP26 (at dilute concentrations) via a slow dialysis method produced highly ordered polymer vesicles 200-250 nm in size under thermodynamic control. The size could be tuned via competitive hydrophobic interactions using polystyrene. In contrast, kinetic control via a rapid precipitation method yielded 5-20 nm micelles.X113331sciescopu

Parameters Influencing the Molecular Weight of 3,6-Carbazole-Based D-pi-A-Type Copolymers

Condensation copolymerization reactions of carbazole 3,6-diboronate with 4,7-bis(5-bromo-2-thienyl)-2,1,3-benzothiadiazole (DTBT) only produce low-molecular-weight donor (D)-pi-acceptor (A) copolymers. High-molecular-weight copolymers for use in optoelectronic devices are necessary for achieving extended pi-conjugation and for controlling the copolymer processibility. To elucidate the cause of the persistently low molecular weight, we synthesized three 3,6-carbazole-based D-A copolymers using copolymerizations of N-9'-heptadecanyl-3,6-carbazole with DTBT, N-9'{2-[2-(2-methoxyethoxy)-ethoxy]-ethyl}-3,-6-carbazole with DTBT, and N-9'-heptadecanyl-3,6-carbazole with alkyl-substituted DTBT. We investigated several parameters for their influence on molecular copolymer weight, including the conformation of the chain during growth, the solubility of the monomers, and the dihedral angles between the donor and acceptor units. Size exclusion chromatography, UV-vis absorption spectroscopy, and computational studies revealed that the low molecular weights of 3,6-carbazole-based D-A copolymers resulted from conjugation breaks and the resulting high coplanarity, which led to strong interactions between polymer chains. These interactions limited formation of high-molecular-weight-copolymers during copolymerization. The strong intermolecular interactions of the 3,6-carbazole moiety were exploited by incorporating 3,6-carbazole units into poly[9',9'-dioctyl-2,7-flourene-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] prepared from 9',9'-dioctyl-2,7-flourene and DTBT. Interestingly, the number average molecular weight increased gradually with increasing 2,7-fluorene monomer content but the number of conjugation breaks was a range of 6-7. The hole mobilities of the copolymers were studied for comparison purposes. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 4368-4378, 2011X111314sciescopu

Dopant-free polymeric hole transport materials for highly efficient and stable perovskite solar cells

We report a dopant-free polymeric hole transport material (HTM) that is based on benzo[1,2-b:4,5:b']-dithiophene and 2,1,3-benzothiadiazole, which results in highly efficient and stable perovskite solar cells (similar to 17.3% for over 1400 h at 75% humidity). The HTM comprises a random copolymer (RCP), which is characterized using UV-vis absorption spectroscopy, cyclic voltammetry, space-charge-limited current, and grazing-incidence wide-angle X-ray scattering. The RCP-based perovskite solar cell exhibits the highest efficiency (17.3%) in the absence of dopants [lithium bis (trifluoromethanesulfonyl) imide and tert-butylpyridine]. The observed efficiency is attributed to a deep HOMO energy level and high hole mobility. In addition, the long-term stability of the device is dramatically improved by avoiding deliquescent or hygroscopic dopants and by introducing a hydrophobic polymer layer. RCP devices maintain their initial efficiency for over 1400 h at 75% humidity, whereas devices made of HTMs with additives fail after 900 h.1111678Nsciescopu

Synthesis and Self-Assembly of Thiophene-Based All-Conjugated Amphiphilic Diblock Copolymers with a Narrow Molecular Weight Distribution

A series of amphiphilic poly­(3-hexylthiophene-<i>b</i>-3-(2-(2-{2-[2-(2-methoxy–ethoxy)-ethoxy]-ethoxy}-ethyl))­thiophene) (P­(3HT-<i>b</i>-3EGT)) polymers was synthesized via a nickel-catalyzed quasi-living polymerization. Size exclusion chromatograms (SEC) revealed that the molecular weight distributions of the <b>P3HT</b> blocks in the block copolymers were comparable with those of the polystyrene standard (monodisperse). ¹H NMR spectra revealed that the <b>P3HT</b> and <b>PEGT</b> units in the block copolymers were well-defined and did not form compositionally mixed regions at the boundary between the blocks and the highly regioregular <b>P3HT</b> units. The correlations among the block ratio, the amphiphilicity, and the self-assembled nanostructures of the block copolymers in thin films and in solution were examined. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) studies revealed that the crystallinity of the <b>BP93</b> composed of 93 mol % <b>P3HT</b> blocks was higher than the crystallinity of the <b>P3HT</b> alone due to the packing effects caused by repulsion among the hydrophobic hexyl and hydrophilic ethylene glycol oligomer side chains. A long relaxation time was required to observe the ordering among <b>P3HT</b> blocks in the <b>BP26</b> composed of 26 mol % P3HT blocks, suggesting that self-assembly could occur if induced on the molecular level. We demonstrated that the molecular-level self-assembly of <b>BP26</b> (at dilute concentrations) via a slow dialysis method produced highly ordered polymer vesicles 200–250 nm in size under thermodynamic control. The size could be tuned via competitive hydrophobic interactions using polystyrene. In contrast, kinetic control via a rapid precipitation method yielded 5–20 nm micelles

The Impact of Multifunctional Ambipolar Polymer Integration on the Performance and Stability of Perovskite Solar Cells

Effective passivation of grain boundaries in perovskite solar cells is essential for achieving high device performance and stability. However, traditional polymer-based passivation strategies can introduce challenges, including increased series resistance, disruption of charge transport, and insufficient passivation coverage. In this study, a novel approach is proposed that integrates a multifunctional ambipolar polymer into perovskite solar cells to address these issues. The ambipolar polymer is successfully incorporated into both the perovskite film and the hole transport layer (HTL), enabling comprehensive restoration of defect sites within the perovskite active layer. Moreover, this approach yields additional advantages for perovskite devices, such as enabling bidirectional charge transport, limiting pinhole formation at the HTL, reducing lithium-ion migration from the HTL to the perovskite, and minimizing both the band offset and surface energy difference between the perovskite film and HTL interface. With these benefits, the ambipolar polymer integrated device achieves a power conversion efficiency (PCE) of 24.0%. Remarkably, it also exhibits enhanced long-term stability, preserving 92% of its initial PCE after 2000&nbsp;h under ambient conditions, and 80% of its initial PCE after 432&nbsp;h under harsh conditions (at 85&nbsp;°C and 85 ± 5% RH). © 2023 Wiley-VCH GmbH.FALS