Low-Temperature Processed Efficient and Reproducible Blade-Coating Organic Photovoltaic Devices with γ-Position Branched Inner Side Chains-Containing Nonfullerene Acceptor

Efficient silver nanowires/cellulose electrothermal material with enhanced stability for printable chameleon-inspired camouflage device

Stimuli-responsive camouflage systems with printable architectures and long-term stability are of paramount importance in advanced military applications. In such adaptive camouflage devices, the stimulus-responsive layer that modulates chromatic properties plays a pivotal role. A critical challenge in electrothermal-actuated camouflage systems lies in mitigating the aggregation and enhancing the temporal stability of solution-processed silver nanowires (AgNWs) employed as the active stimulus layer. Herein, we report a rationally designed composite system comprising AgNWs and hydroxypropyl methylcellulose (HPMC), which demonstrates significantly enhanced electrothermal efficiency and operational stability through synergistic thermal management and intermolecular engineering. The incorporation of cellulose matrices in the AgNWs/HPMC composite exhibits substantially lower thermal conductivity compared to AgNWs networks, effectively reducing the heat-transfer coefficient of the electrothermal system. This modification facilitates controlled thermal dissipation from the heating element to the ambient environment, substantially augmenting the electrothermal conversion efficiency. Moreover, the molecular-level interactions between the hydroxyl moieties (C-OH) of HPMC and the carbonyl groups (CO) of AgNWs significantly enhance the spatial uniformity and temporal stability of the electrothermal system. Quantitative analysis reveals that the AgNWs/HPMC heater achieves a 163.2 % increase in temperature elevation compared to conventional AgNWs heaters under identical conditions (3 V, 90 s). The optimized composite system maintains consistent electrothermal performance over 138 days under atmospheric conditions, whereas the control system exhibits complete performance degradation within 5 days. Furthermore, we demonstrate an all-printable multilayer biomimetic device incorporating the AgNWs/cellulose composite as the thermal stimulus layer, achieving rapid chromatic modulation (< 5 s) at ultra-low operating voltages (< 1 V) for efficient environmental adaptation. This work establishes both theoretical foundations for high-performance, stable printable electrothermal materials and provides innovative strategies for fabricating next-generation adaptive camouflage systems.

Simultaneous enhancement of efficiency, stability and stretchability in binary polymer solar cells with a three-dimensional aromatic-core tethered tetrameric acceptor

Polymer solar cells (PSCs) leverage blend films from polymer donors and small-molecule acceptors (SMAs), offering promising opportunities for flexible power sources. However, the inherent rigidity and crystalline nature of SMAs often embrittle the polymer donor films in the constructed bulk heterojunction structure. To address this challenge, we improved the stretchability of the blend films by designing and synthesizing a tethered giant tetrameric acceptor (GTA) with increased molecular weight that promotes entanglement of individual SMA units. The key to this design is using tetraphenylmethane as the linking core to create a three-dimensional and high C2 symmetry structure, which successfully regulates their aggregation and relaxation behavior. With GTA as the acceptor, its blend films with polymer donor PM6 exhibit significantly improved stretchability, with nearly a 150% increase in crack onset strain value compared to PM6:Y6. Moreover, the PSCs achieve an increased efficiency of up to 18.71% and demonstrate outstanding photostability, maintaining >90% of their initial power conversion efficiency after operating for over 1000 hours. Our findings demonstrate that by specifically designing three-dimensional tethered SMAs and aligning their molecular weights more closely with those of polymer counterparts, we can achieve enhanced stretchability without compromising morphological stability or device efficiency.

Constraining the Excessive Aggregation of Non-Fullerene Acceptor Molecules Enables Organic Solar Modules with the Efficiency >16

Translating high-performance organic solar cell (OSC) materials from spin-coating to scalable processing is imperative for advancing organic photovoltaics. For bridging the gap between laboratory research and industrialization, it is essential to understand the structural formation dynamics within the photoactive layer during printing processes. In this study, two typical printing-compatible solvents in the doctor-blading process are employed to explore the intricate mechanisms governing the thin-film formation in the state-of-the-art photovoltaic system PM6:L8-BO. Our findings highlight the synergistic influence of both the donor polymer PM6 and the solvent with a high boiling point on the structural dynamics of L8-BO within the photoactive layer, significantly influencing its morphological properties. The optimized processing strategy effectively suppresses the excessive aggregation of L8-BO during the slow drying process in doctor-blading, enhancing thin-film crystallization with preferential molecular orientation. These improvements facilitate more efficient charge transport, suppress thin-film defects and charge recombination, and finally enhance the upscaling potential. Consequently, the optimized PM6:L8-BO OSCs demonstrate power conversion efficiencies of 18.42% in small-area devices (0.064 cm2) and 16.02% in modules (11.70 cm2), respectively. Overall, this research provides valuable insights into the interplay among thin-film formation kinetics, structure dynamics, and device performance in scalable processing.