Two stacking manners, that is, π- and lamellar stacking, are generally found for organic semiconductors, in which the π-stacking occurs between conjugated groups and the lamellar stacking refers to the separation of the conjugated and aliphatic moieties. The stacking principles are yet not well-defined. In this work, extended transition state–natural orbitals for chemical valence (ETS–NOCV), an energy decomposition analysis, is utilized to examine the π- and lamellar stacking for a series of naphthalenetetracarboxylic diimide (R-NDI) crystals. The crucial role of dispersion is validated. The perception that π-stacking is merely determined by the conjugated moiety is challenged. The stacking principles are associated with the closest packing model. Nanoscopic phase separation of conjugated and aliphatic moieties and the formation of lamellar and herringbone motifs in the R-NDIs can thus be clarified. Moreover, the interactions between NDI and the alkyl chain are investigated, revealing that the interactions can be significant, being contradictory to the conventional point of view. Along with R-NDIs, additional organic crystals consisting of various conjugated functionalities and substituents are also investigated by ETS–NOCV. The sampling scope is up to 108 conjugated molecules. The dominant role of dispersion force irrespective of the variation in the conjugated moieties and substituents is further confirmed. It is envisaged that the established principles are applicable to other organic semiconductors. The perspective toward the π- and lamellar stacking might be modified, paving the way for ultimate morphological control.

A novel non‐volatile additive, fluorinated bis(perfluorophenyl)pimelate (BF7), is demonstrated to effectively improve both the efficiency and thermal stability of a highly efficient organic solar cell (OSC), comprising fluorinated Y6 as the small‐molecule acceptor and PM6 as the polymer donor. Processed with optimized 0.5 wt% BF7 in solution, the PM6:Y6:BF7 device achieves an elevated power conversion efficiency (PCE) of 17.01%, compared to 15.16% of that processed without BF7. Moreover, the BF7‐elevated PCE can sustain 95% of the best PCE over 100 °C annealing for 72 h. Grazing incidence X‐ray scattering and differential scanning calorimetry results consistently indicate that BF7 in the PM6:Y6:BF7 device interacts preferentially with Y6, resulting in improved fractal‐like network structures of the active layer with optimized size and orientation of Y6 nano‐crystallites and elevated thermal stability. Molecular simulation also supports that the observed structure and thermal stability is associated with the F–π noncovalent supramolecular interactions between the perfluorophenyl moieties of BF7 and difluorophenyl‐based FIC‐end‐groups of Y6. Similar bifunctional BF7 effects are also observed in the well‐known PM6:IT‐4F system, suggesting that adding BF7 for concomitantly improved PCE and thermal stability might extend generally to OSCs that feature small molecule acceptors of difluorophenyl end‐groups.

A first-generation Grubbs catalyst has been shown to not only catalyze the ring opening metathesis polymerization (ROMP) of cyclopropene derivatives but also differentiate E- and Z-double bonds in intermediates by different reaction patterns, leading to stereospecific synthesis of poly­(methylene-E-vinylene). The intermediate with the Z-double bond formed during the course of ROMP of cyclopropene is sensed by the catalyst, chopped by the catalyst, and removed as the cyclohexadiene derivative, and in the meantime, a ruthenium–carbene species is regenerated for continuing polymerization. When a second-generation Grubbs catalyst is used, a cyclic polymer with all double bonds in the trans configuration is obtained as the sole polymeric product, in addition to the same cyclohexadiene derivative as described above. The degree of polymerization in the latter reaction is independent of the loading of the catalyst. The formation of cyclic polymer is not common and the mechanism thereof remains unclear. One possibility would be a change in conformation of the alkenyl substituents on azetidine rings that would result in alteration of the folding nature of the polymer, leading to a cyclic polymer via ring closure metathesis.

the source-drain electrodes. [4] Since the in-plane π-stacking is in line with the source and drain electrodes, likely further boosting the intermolecular charge transport along the two electrodes, the design principles toward conjugated polymers targeting at high OFET mobilities are thus directed to the establishment of extensive edge-on π-order. [5] Nevertheless, the longstanding principles have been challenged by several studies, in which decent hole or electron mobilities were achieved in the absence of the requirements. [6] Another emerging design principles are thus developed, stating that efficient charge transport in the polymer semiconducting layer can be accomplished through the interconnected short-range-order crystallites. [7] Conjugated polymers normally contain conjugated and aliphatic functionalities. [8] The aliphatic functionality is considered to be non-conductive. [9] It is envisioned that the interconnection among polymer crystallites encouraging the charge transport should primarily derive from the conjugated functionality. Herein it is coined as π-interconnection. In our interpretation, π-order and π-interconnection both stem from π-stacking. The crucial distinction lies in the degree of orderliness. In comparison with the π-order, the π-stacking in the π-interconnection is sporadic rather than periodic. On the other hand, our previous theoretical investigation sheds light on the stacking principles for π-stacking in organic semiconductors, suggesting that the resemblance in the molecular shape is responsible for the establishment of π-stacking. [10] It can thus be envisaged that for a given conjugated polymer with long aliphatic side chains, the fractional substitution of long side chains by short ones would give rise to the monomeric units with two different molecular figures, reducing the π-order. Moreover, the presence of short side chains might be advantageous to the building of π-interconnection due to the ease of steric repulsion. Fractional side-chain truncation could be a straightforward approach to regulating the proportion of π-order to π-interconnection.In this work, 2,6-dibromonaphthalene-1,4,5,8-tetracarboxylic-N,N′-bis(2-octyldodecyl) diimide (Br-NDI2OD-Br), 2,6-dibromonaphthalene-1,4,5,8-tetracarboxylic-N,N′-bis(butyl) diimide (Br-NDIBu-Br), and 5,5′-bis(trimethylstannyl)-2,2′-bithiophene were copolymerized by the Stille polycondensation [11] ( Table 1). The fraction of Br-NDI2OD-Br to Br-NDIBu-Br was adjusted to give numerous co-polymers with various amounts of NDIBu moiety in the polymer chain. The electronic properties of the Conventional design principles toward conjugated polymers aiming at high organic field-effect-transistor (OFET) mobilities are directed at the establishment of extensive edge-on π-order. However, emerging principles state that efficient charge transport can be established through interconnected short-range-order polymer crystallites. Fractional side-chain truncation has been employed to furnish numerous polymers. The electronic structures of th...

In this work, P(NDI2OD-T2) was blended with various amounts of PEO, aPP, or iPP to furnish numerous thin films. The morphology of pristine P(NDI2OD-T2) and the blends was investigated by X-ray photoelectron spectroscopy, grazingincidence X-ray scattering (GIXS), near-edge X-ray absorption fine structure spectroscopy, UV−vis spectroscopy, and atomic force microscopy, revealing that the aggregation of P(NDI2OD-T2) is adjustable, and the interconnected P(NDI2OD-T2) domain can be readily achieved. Furthermore, the transformation of P-(NDI2OD-T2) from face-on to edge-on crystallites was observed at a specific blend. A rationale by adopting the geometric shape of crystallite is proposed to account for this transformation. P(NDI2OD-T2) and the blends were submitted to organic field-effect transistor fabrication in the bottom-gate/top-contact geometry. The relationship between the electron mobility and the GIXS morphological characteristics is established. According to the fitting equation, the π stacking and polymer backbone of P(NDI2OD-T2) play significant roles in determining the electron mobility.

Conjugated polyelectrolytes have been utilized in applications including chemical/biosensing, [30][31][32] cell imaging, [33][34][35] and disease diagnosis/therapy. [36,37] Their synthesis comprises the preparation of organic-soluble conjugated polymers followed by post-functionalization. A typical post-functionalization reaction is the nucleophilic substitution of an alkyl-bromide with amines to afford ammonium salts, which render the resultant conjugated polyelectrolytes aqueous soluble. However, post-functionalization exhibits poor conversion with many unreacted reaction sites. Aqueous polymerization of water-soluble monomers is an alternate approach realized through Heck, [38,39] Sonogashira, [40,41] Suzuki, [42,43] and FeCl 3 -mediated oxidative [44,45] polymerizations. These reactions are successful when the active species tolerates the presence of water.Reports of aqueous palladium-catalyzed DArP are scarce. [9,46,47] DArP also requires a carbonate base and carboxylic acid additive. Compared to water, carbonate bases display higher Lewis basicities, while carboxylic acids are more acidic. Palladium species preserve the reactivity in the presence of carbonates and carboxylic acids, making them tolerant to water. This study examines the aqueous palladium-catalyzed DArP of 2-bromothiophene derivatives, T1 and T2. The initially selected ligand, triphenylphosphine-3,3′,3″-trisulfonic acid trisodium salt (m-TPPTs), was functional in the DArP; however, its separation from the resultant polymers by dialysis was challenging due to its strong aggregation in water and N,N-dimethylacetamide (DMAc). This was supported by dynamic light scattering (DLS), X-ray crystallography, and gel permeation chromatography (GPC). Thus, pyrimidine-Pd(OAc) 2 was employed in the DArP of T1 to afford PT1 with no ligand (pyrimidine) contamination. Density functional theory (DFT) binding energy calculations revealed that the coordinating ability to palladium was of the order carboxylate > pivalic acid (PivOH) > water, rationalizing the feasibility of executing DArP in water. Finally, the polyelectrolyte molecular-weight overestimation by GPC in water was attributed to the polyelectrolyte effect. Experimental results indicated that the conjugated polyelectrolytes aggregate in DMAc to form a folding structure with the polar groups pointing outwards and conjugated moieties directed inwards, corresponding to a reduced hydrodynamic volume. The polyelectrolyte molecular weight and dispersity (Đ) values determined by GPC in DMAc were, therefore, questionable.

Blending has been used extensively to meet the requirements for high‐mobility organic field‐effect transistors (OFETs), involving various combinations of (non‐)conjugated polymers and (non‐)conjugated molecules. Nonetheless, the collaborative effects of conjugated polymer and its structurally analogous molecule on charge‐transport properties have rarely been reported. In this work, P(NDI2OD‐T2) and N,N′‐bisbutyl‐2,6‐bis([2,2′]bithiophenyl‐5‐yl)‐1,4,5,8‐naphthalene diimide (M), are synthesized and blended with each other. M is designed to resemble the monomeric unit of P(NDI2OD‐T2) on the basis of the premise that structural similarity would promote their compatibility in the blends. This compatibility preserves electronic coupling through intermolecular interaction and establishes charge‐transport pathways as well. Overall, the thin‐film morphology of the blends could be prudently regulated through controlling the blending fraction, resulting in raising electron mobility up to ≈0.3 cm2 V−1 s−1. More importantly, this approach reduces threshold voltage by 50%, originating from lowering the injection barrier. These findings are well rationalized and the promising capabilities of the compatibility principle in OFETs are strongly supported.

Conversion of CO2 into carbonaceous fuels with the aid of solar energy has been an important research subject for decades. Owing to their excellent electron‐accepting capacities, fullerene derivatives have been extensively used as n‐type semiconductors. This work reports that the fulleropyrrolidine functionalized with 4,7‐di(thiophen‐2‐yl)benzo[c][1,2,5]thiadiazole, abbreviated as DTBT‐C60, could efficiently catalyze the photoreduction of CO2 to CO. The novel C60‐chromophore dyad structure facilitated better usage of solar light and effective dissociation of excitons. Consequently, the DTBT‐C60 exhibited a promising CO yield of 144 μmol gcat−1 under AM1.5G solar illumination for 24 h. Moreover, the isotope experiments demonstrated that water molecules could function as an electron source to reactivate DTBT‐C60. Impressively, DTBT‐C60 exhibited an extremely durable catalytic activity for more than one week, facilitating the practical application of photochemical CO2 reaction.