To Reveal the Importance of the Crystallization Sequence on Micro-Morphological Structures of All-Crystalline Polymer Blends by In Situ Investigation

Increasing the Content of Edge-On Orientation to Improve the Hole Mobility of IDTBT Film by the van der Waals Interaction between the Side Chain and Alkane Additives

The molecular orientation in the conjugated polymer film critically impacts the performance of organic electronic devices. As for organic field-effect transistors (OFETs), the edge-on orientation is beneficial for efficient interchain charge transport. However, for the near amorphous indacenodithiophene-co-benzothiadiazole (IDTBT) film, the face-on orientation was dominated in the drop cast thin film. Herein, we proposed a strategy to increase the edge-on orientation in IDTBT films by inserting n-hexadecane (16C) additives with a high boiling point between the side chains. Because the 16C additives had a similar structure to that of the side chain, the 16C additives were distributed around the side chain in the nucleation stage. Then, the backbone aggregated quickly with the nuclei formation speed (k) nearly twice as high as that without the 16C additives. In the growth stage, some face-on nuclei turned to edge-on nuclei due to the van der Waals interactions between the side chain and 16C additives. This was verified by the results of in situ GIWAXS, where the intensity of (010) decreased and the intensity of (100) increased in the out-of-plane direction. The edge-on orientation content of the film with 16C additives reached 57%, higher than that of the neat film (33%). Moreover, compared to the neat IDTBT film, the lamellar packing distance of the film with 16C additives increased the lamellar packing distance from 16.97 to 23.26 Å and the π-π stacking distance decreased from 4.36 to 4.19 Å. The hole mobility of the film with 16C additives (3.24 ± 0.19 cm2 V-1 s-1) was higher than that of the neat film (0.94 ± 0.07 cm2 V-1 s-1).

Morphology Tuning via Linker Modulation: Metal-Free Covalent Organic Nanostructures with Exceptional Chemical Stability for Electrocatalytic Water Splitting

The development of synthetic routes for the formation of robust porous organic polymers (POPs) with well-defined nanoscale morphology is fundamentally significant for their practical applications. The thermodynamic characteristics that arise from reversible covalent bonding impart intrinsic chemical instability in the polymers, thereby impeding their overall potential. Herein, a unique strategy is reported to overcome the stability issue by designing robust imidazole-linked POPs via tandem reversible/irreversible bond formation. Incorporating inherent rigidity into the secondary building units leads to robust microporous polymeric nanostructures with hollow-spherical morphologies. An in-depth analysis by extensive solid-state NMR (1D and 2D) study on 1H, 13C, and 14N nuclei elucidates the bonding and reveals the high purity of the newly designed imidazole-based POPs. The nitrogen-rich polymeric nanostructures are further used as metal-free electrocatalysts for water splitting. In particular, the rigid POPs show excellent catalytic activity toward the oxygen evolution reaction (OER) with long-term durability. Among them, the most efficient OER electrocatalyst (TAT-TFBE) requires 314 mV of overpotential to drive 10 mA cm-2 current density, demonstrating its superiority over state-of-the-art catalysts (RuO2 and IrO2).

Enhancing the Molecular Order and Vertical Component Distribution of the P3HT/O-IDTBR System during Layer-by-Layer Processing

The molecular order and vertical component distribution are critical to enhance the charge transport in layer-by-layer (LbL) processed active layer. However, the excessive inter-diffusion between donor and acceptor layers during LbL processing irrepressibly reduces their ordered packing. Herein, a novel tactic to optimize the molecular order and vertical morphology of the active layer through suppressing the deep penetration of (5Z,5'Z)-5,5'-((7,7'-(4,4,9,9-tetraoctyl-4,9-dihydro-s-indaceno[1,2-b:5,6 -b']dithiophene-2,7-diyl)bis(benzo[c][1,2,5]thiadiazole-7,4-diyl))bis(methanylylidene)) bis(3-ethyl-2-thioxothiazolidin-4-one) (O-IDTBR) to poly(3-hexylthiophene) (P3HT) film during LbL processing is proposed. This is enabled by inducing the formation of P3HT nanofibers through ultraviolet (UV) irradiation and solution aging. During the LbL processing, these nanofibers with high crystallinity reduce the damage of O-IDTBR solution to P3HT film and restrict the penetration of O-IDTBR into P3HT matrix. As a result, the P3HT nanofibers are preserved and the degree of vertical phase separation is enlarged in the LbL-processed film. Meanwhile, the molecular order of both components is enhanced. The resulting morphology that featured as intertwined P3HT nanofibers/O-IDTBR network efficiently promotes charge transport and extraction, boosting the power conversion efficiency (PCE) of the devices from 6.70 ± 0.12% to 7.71 ± 0.10%.