The solution‐state aggregation of conjugated polymers critically determines the morphology and performance of organic solar cells (OSCs), yet processing optimization remains largely empirical. Here, we establish the sol–gel transition temperature (Tsol–gel), determined by rheology, as a transferable descriptor linking solution aggregation to film formation and device performance. Using cryo‐electron microscopy (CEM), small‐angle neutron scattering (SANS), and rheology, we reveal that the high‐performance donor polymer D18 in chlorobenzene evolves from dissolved wormlike chains to a weak gel and then to a strong gel upon cooling. Importantly, processing near the Tsol–gel temperature yields weak‐gel aggregates, which transform into a double fibril network during film formation, enabling enhanced charge transport, optimized phase separation, and uniform large‐area coating. Under this condition, D18:L8‐BO achieves a power conversion efficiency of 19.6% in small‐area devices and 17.1% in 17.6 cm2 mini‐modules. More importantly, this Tsol–gel‐guided strategy is further validated in multiple conjugated polymers in OSCs, including PM6, PffBT4T‐2OD, and D18 processed from o‐xylene, where the optimal performance consistently occurs near the corresponding sol–gel transition. These results identify weak‐gel pre‐aggregation near Tsol–gel as a general processing window for constructing favorable fibrillar morphologies and provide a broadly applicable framework for morphology control in high‐performance OSCs.
Cellulose nanocrystals (CNCs) are one of the promising bio‐based nanomaterials with a distinctive chiral nematic structure for fabricating optically iridescent films, yet their long evaporation time for self‐assembly and poor flexibility greatly inhibit practical applications. Herein, pure CNCs and modified CNCs films by various molecules (PEG, glucose, and glycerol) were prepared via evaporation‐induced self‐assembly (EISA) under the regulation of environmental temperature, in order to investigate the synergistic effects of modifiers and temperature gradients on CNCs' self‐assembly and film properties. A series of characterizations revealed that cooperation of PEG may improve CNCs dispersion, while glucose induced excessive hydrogen‐bonded agglomeration. The CNCs/PEG/glucose composite (CGP) films prepared via evaporation at 55°C exhibited optimal applicable performance, with enhanced thermal stability, tensile strength and toughness as compared with pure CNCs and single‐modified films. These results suggest that the dual‐modification system by the ternary molecules achieved a synergistic balance of interparticle interactions, effectively suppressing high‐temperature agglomeration, accelerating self‐assembly and maintaining chiral nematic order. This temperature‐modification synergy strategy provides a feasible approach for the efficient preparation of high‐performance CNCs iridescent films, promoting their applications in flexible, optical, and smart functional materials.
Zhe Ling, Huilin Chen, Yu-Zhen Zhou et al.· Polymer Engineering & Sc...· 0 citations
Addressing the issues of accelerated charge migration and diminished energy storage performance in polyimide (PI) under a high‐temperature electric field, this study proposes an aggregation‐state regulation strategy through the construction of non‐conjugated nanodomains in PI‐based copolymers. By introducing non‐conjugated polydimethylsiloxane (PDMS) diamine into the PI backbone and leveraging the segmental incompatibility between aromatic PI and PDMS segments, a nanoscale “sea‐island” phase‐separated structure is generated based on the enthalpy‐driven phase separation principle. This tailored heterogeneous structure weakens compact aromatic packing, reduces local electronic coupling between PI‐derived segments, and suppresses long‐range charge migration while simultaneously introducing deep trapping sites at heterogeneous interfaces, thereby synergistically regulating charge diffusion behavior of the PI‐PDMS copolymer. The resultant PI‐PDMS film exhibits outstanding performance over a wide‐temperature range: a dielectric constant of 4.41 with low loss of <0.015 at 100 Hz, a discharged energy density of 16.2 J/cm
3
with efficiency of > 90% at 950 MV/m and 25°C, and 6.6 J/cm
3
with efficiency of > 90% at 600 MV/m and 200°C. This research establishes a fresh paradigm for the design of high‐performance polymer dielectrics through aggregation‐state regulation.
Flexible conductive hydrogels are often hindered by non‐green fabrication, performance trade‐offs, and additive‐dependent functionalization. Herein, we establish a triple strategy of “green preparation–structural synergy–multifunctional integration”. With wood vinegar, deep eutectic solvent, polyvinyl alcohol, chitosan, and tetraethoxysilane as raw materials, the target hydrogel is fabricated via a one‐pot route without toxic auxiliary reagents. The interpenetrating network constructed by rigid inorganic sites and flexible polymer chains endows the material with excellent low‐temperature tolerance down to −20°C, high ionic conductivity of 38.1 mS cm−1, and robust mechanical properties. When used as a gel electrolyte in symmetric supercapacitors, the device achieves an energy density of 7.49 Wh kg−1 and maintains stable cycling over 10 000 times. As a flexible strain sensor, it could capture subtle physical movements for precise Morse code recognition assisted by deep learning. A self‐powered sensing system is fabricated by vertically stacking the supercapacitor and hydrogel sensor, which outputs distinct current signals in response to various deformations. Preliminary explorations in array sensing, encrypted communication and manipulator control further validate the great potential of this hydrogel for constructing an integrated “material–device–system” platform, providing a feasible strategy for developing eco‐friendly, integrative, and intelligent flexible electronics.
Zeyu Chang, Rong Dong, Xiaofeng Sun et al.· Advanced Functional Material...· 1 citation
Room temperature phosphorescent (RTP) hydrogels have garnered extensive attraction owing to their distinctive optical properties, low toxicity and cost-effectiveness. However, achieving efficient and long-lived afterglow emission in hydrogel systems remains a formidable challenge due to the severe quenching of triplet excitons by water molecules. Herein, taking inspiration from stimuli-responsive luminescent behavior of jellyfish, we propose a solvent exchange strategy to construct a cellulose-based RTP gel with polyethylene glycol (PEG)-induced phosphorescent behavior. Specifically, a cellulose/polyvinyl alcohol (PVA) double-network hydrogel system was constructed to confine carbon dots (CDs) within a rigid matrix, which preliminarily enabled phosphorescence emission. Driven by phase separation induced by PEG, the resulting gel with ultra-strong hydrogen-bonded networks exhibits green RTP emission with an extended lifetime of 255.55 ms and a tensile strength of 3.79 MPa, representing 370-fold and 17-fold enhancements, respectively, compared to the gel prepared using water as the solvent. Furthermore, the phosphorescent properties of the gel can be tuned by adjusting the molecular weight of PEG. Taking advantage of these properties, the cellulose-based RTP gels were further fabricated into various luminescent materials, which exhibited promising potential for information encryption and advanced anti-counterfeiting applications.
Cong Li, Yifan Liu, Xuewei Tian et al.· International Journal of Bio...· 0 citations
The performance of organic solar cells (OSCs) is critically governed by the fibrillar organization of bulk-heterojunction active layers, yet controlling long-range, directional fibrillar morphology under nonequilibrium processing remains challenging. Here we report that two-dimensional cobalt phosphosulfide (CoPS3) nanocrystals act as kinetic templates that reprogram molecular self-assembly during film formation. Through collective electronic interactions with conjugated polymer donors and small-molecule acceptors, CoPS3 modulates molecular densification and phase separation pathways, enabling refined, long-range fibrillar networks without increasing crystallinity. The resulting morphology enhances exciton dissociation and charge transport, and inhibits recombination, delivering a power conversion efficiency of 21.0%. This templating strategy is effective across multiple OSC systems, simultaneously improving efficiency and storage stability, offering a promising route for kinetic morphology control in organic optoelectronics. Controlling long-range, directional fibrillar morphology is important for organic solar cells (OSC). Here, the authors show that cobalt phosphosulfide nanocrystals can template film formation in OSCs, improving charge generation and transport, and achieving a power conversion efficiency of 21.0%.
Poly (vinyl alcohol) (PVA), a representative biodegradable and water‐soluble polymer, suffers from high crystallinity, a strength‑toughness trade‑off, and poor thermal stability arising from strong interchain hydrogen bonding. Conventional modification strategies fail to simultaneously achieve synergistic enhancement of strength‐toughness and functionalization, severely restricting its engineering applications. Herein, inspired by the robust yet dynamic nature of cation‐π interactions, we present a universal design strategy for high‐performance water‐soluble polymers based on indole‐Mg2+ cation‐π dynamic cross‐linking. Molecular simulations and spectroscopic characterization demonstrate that Mg2+ forms strong cation‐π interactions with indole moieties, exhibiting a binding energy of −113 kJ mol−1. Mechanical testing reveals that the optimally formulated PVAI‐7.5%Mg2+ film achieves a tensile strength of 51 MPa (a 130% increase from 22 MPa) and an elongation at break of 400% (enhanced from 320%), thereby realizing synchronous improvement of strength and toughness. Benefiting from the dynamic reversibility of cation‐π interactions, the film exhibits autonomous scratch healing within 12 h at room temperature without external stimuli, while retaining excellent water solubility that enables multiple recovery and reprocessing cycles via solvent‐based methods without performance degradation. This study overcomes the dual bottlenecks of the strength‐toughness trade‐off and the performance‐functionalization incompatibility inherent to PVA modification, offering new avenues for the high‐performance and multifunctional design of water‐soluble polymers and providing experimental and theoretical insights into the application of cation‐π interactions in polymeric materials.
Yang Xu, Jin-Ping Yu, Yi-Wen Lu et al.· Macromolecular rapid communi...· 0 citations
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