Now showing 1 - 10 of 11
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Bioinspired soft robots based on organic polymer-crystal hybrid materials with response to temperature and humidity

2023, Yang, Xuesong, Lan, Linfeng, Pan, Xiuhong, Di, Qi, Liu, Xiaokong, Li, Liang, Naumov, Panče, Zhang, Hongyu

The capability of stimulated response by mechanical deformation to induce motion or actuation is the foundation of lightweight organic, dynamic materials for designing light and soft robots. Various biomimetic soft robots are constructed to demonstrate the vast versatility of responses and flexibility in shape-shifting. We now report that the integration of organic molecular crystals and polymers brings about synergistic improvement in the performance of both materials as a hybrid materials class, with the polymers adding hygroresponsive and thermally responsive functionalities to the crystals. The resulting hybrid dynamic elements respond within milliseconds, which represents several orders of magnitude of improvement in the time response relative to some other type of common actuators. Combining molecular crystals with polymers brings crystals as largely overlooked materials much closer to specific applications in soft (micro)robotics and related fields.

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Revealing Size‐Dependency of Ionic Liquid to Assist Perovskite Film Formation Mechanism for Efficient and Durable Perovskite Solar Cells

2023, Li, Liang, Wang, Fei, Zhou, Kang, Liang, Xiao, Zhou, Xianfang, Duan, Dawei, Ge, Chuangye, Zhang, Xintao, Shi, Yumeng, Lin, Haoran, Zhu, Quanyao, Hu, Hanlin, Zhang, Hongyu

Ionic liquids (ILs) are extensively utilized for the manipulation of crystallization kinetics of perovskite, morphology optimization, and defect passivation for the fabrication of highly efficient and stable devices. However, comparing ILs with different chemical structures and selecting the appropriate ILs from the many types available to enhance perovskite device performance remains a challenge. In this study, a range of ILs containing different sizes of anions are introduced as additives for assisting in film formation in perovskite photovoltaics. Specifically, ILs with various sizes significantly affects the strength of chemical interaction between ILs and perovskite composition, inducing varying degrees of conversion of lead iodide to perovskite as well as the formation of perovskite films with markedly disparate grain sizes and morphology. Theoretical calculations in conjunction with experimental measurements revealed that small-sized anion can more effectively reduce defect density by filling halide vacancies within perovskite bulk materials, resulting in suppression of charge-carrier recombination, an extended photoluminescence lifetime, and significantly improved device performance. Boosted by ILs with appropriate size, the champion power conversion efficiency of 24.09% for the ILs-treated device is obtained, and the unencapsulated devices retain 89.3% of its original efficiency under ambient conditions for 2000 h.

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Electrically conductive hybrid organic crystals as flexible optical waveguides

2022, Li, Liang, Yang, Xuesong, Lan, Linfeng, Pan, Xiuhong, Liu, Xiaokong, Song, Yilong, Yang, Xueying, Dong, Qingfeng, Naumov, Panče, Zhang, Hongyu

Hybrid materials capitalize on the properties of individual materials to attain a specific combination of performance assets that is not available with the individual components alone. We describe a straightforward approach to preparation of sandwich-type hybrid dynamic materials that combine metals as electrically conductive components and polymers as bending, momentum-inducing components with flexible organic crystals as mechanically compliant and optically transducive medium. The resulting hybrid materials are conductive to both electricity and light, while they also respond to changes in temperature by deformation. Depending on the metal, their conductivity ranges from 7.9 to 21.0 S µm. The elements respond rapidly to temperature by curling or uncurling in about 0.2 s, which in one typical case corresponds to exceedingly fast deformation and recovery rates of 2187.5° and 1458.3° , respectively. In cyclic operation mode, their conductivity decreases less than 1% after 10,000 thermal cycles. The mechanothermal robustness and dual functionality favors these materials as candidates for a variety of applications in organic-based optics and electronics, and expands the prospects of application of organic crystals beyond the natural limits of their dynamic performance.

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A Low-Temperature-Resistant Flexible Organic Crystal with Circularly Polarized Luminescence

2022, Li, Liang, Pan, Xiuhong, Zheng, Anyi, Di, Qi, Duan, Pengfei, Ye, Kaiqi, Naumov, Panče, Zhang, Hongyu, Yu, Xu

Flexible organic crystals with unique mechanical properties and excellent optical properties are of paramount significance for their wide applications in various research fields such as adaptive optics and soft robotics. However, low-temperature-resistant flexible organic crystal with circularly polarized luminescence (CPL) ability has never been reported. Herein, chiral organic crystals with CPL activity and low-temperature flexibility (77 K) are fabricated by the solvent diffusion method from chiral Schiff bases, S(R)-4- b romo-2-(((1- p henyl e thyl)imino) m ethyl) p henol (S(R)-BPEMP). The corresponding chiroptical properties for the two enantiomeric crystals were thoroughly investigated, including the measurements of circular dichroism (CD) and CPL. To the best of our knowledge, this is the first report on low-molecular-weight flexible organic crystals with CPL activity, and we believe that the results will give a new impetus to the research of organic crystals.

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Collective photothermal bending of flexible organic crystals modified with MXene-polymer multilayers as optical waveguide arrays

2023, Yang, Xuesong, Lan, Linfeng, Li, Liang, Yu, Jinyang, Liu, Xiaokong, Tao, Ying, Yang, Quan-Hong, Naumov, Panče, Zhang, Hongyu

The performance of any engineering material is naturally limited by its structure, and while each material suffers from one or multiple shortcomings when considered for a particular application, these can be potentially circumvented by hybridization with other materials. By combining organic crystals with MXenes as thermal absorbers and charged polymers as adhesive counter-ionic components, we propose a simple access to flexible hybrid organic crystal materials that have the ability to mechanically respond to infrared light. The ensuing hybrid organic crystals are durable, respond fast, and can be cycled between straight and deformed state repeatedly without fatigue. The point of flexure and the curvature of the crystals can be precisely controlled by modulating the position, duration, and power of thermal excitation, and this control can be extended from individual hybrid crystals to motion of ordered two-dimensional arrays of such crystals. We also demonstrate that excitation can be achieved over very long distances (>3 m). The ability to control the shape with infrared light adds to the versatility in the anticipated applications of organic crystals, most immediately in their application as thermally controllable flexible optical waveguides for signal transmission in flexible organic electronics.

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Packing-Dependent Mechanical Properties of Schiff Base Crystals

2022, Li, Liang, Lan, Linfeng, Di, Qi, Liu, Bin, Xu, Yu-xin, Naumov, Panče, Zhang, Hongyu

Flexible luminescent crystals endowed with mechanical compliance are emerging as materials that could be the foundation of future lightweight single-crystal flexible optoelectronics. Multiple mechanical responses (for example, elastic and plastic deformation) are rarely observed with the same material among the reported examples of such materials. Here, we report a Schiff base, (Z)-3-(4-ethoxyphenyl)-2-(4-(((E)-2-hydroxy-5-methoxybenzylidene)amino)phenyl)acrylonitrile, which crystallizes as two polymorphs and one tetrahydrofuran solvate. All three forms are emissive, but they have different mechanical properties. Specifically, two of the forms that are unsolvated polymorphs (denoted A and B) were found to be brittle and plastic, respectively, while the third form, which is a solvate (denoted C), showed excellent elasticity. Notably, form C becomes plastic after the crystal is desolvated. Single-crystal X-ray diffraction (SCXRD) and mechanical testing were performed to obtain better insight into the root-cause for the observed difference in mechanical properties. Since crystals of forms B and C are mechanically compliant as well as optically transparent, they were tested as flexible single-crystal optical waveguides.

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Remote and precise control over morphology and motion of organic crystals by using magnetic field

2022, Li, Liang, Yang, Xuesong, Lan, Linfeng, Liu, Xiaokong, Naumov, Panče, Zhang, Hongyu

Elastic organic crystals are the materials foundation of future lightweight flexible electronic, optical and sensing devices, yet precise control over their deformation has not been accomplished. Here, we report a general non-destructive approach to remote bending of organic crystals. Flexible organic crystals are coupled to magnetic nanoparticles to prepare hybrid actuating elements whose shape can be arbitrarily and precisely controlled simply by using magnetic field. The crystals are mechanically and chemically robust, and can be flexed precisely to a predetermined curvature with complete retention of their macroscopic integrity at least several thousand times in contactless mode, in air or in a liquid medium. These crystals are used as optical waveguides whose light output can be precisely and remotely controlled by using a permanent magnet. This approach expands the range of applications of flexible organic crystals beyond the known limitations with other methods for control of their shape, and opens prospects for their direct implementation in flexible devices such as sensors, emitters, and other (opto)electronics.

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Repair and Splicing of Centimeter‐Size Organic Crystalline Optical Waveguides

2023, Lan, Linfeng, Li, Liang, Yang, Xuesong, Naumov, Panče, Zhang, Hongyu

Organic single crystals that are capable of transmitting light and charge are quickly shaping into a new forefront of research in photoelectronic materials that is thought to hold a tremendous potential for the broader field of organic electronics. However, one of the main disadvantages that currently stands against the direct application of organic single crystals in that capacity is their pronounced proneness to mechanical damage due to brittleness, abrasion, and wear. To account for this drawback, here a simple and universal strategy is proposed for the recovery of macroscopic integrity of cracked or completely fractured crystals based on the layer-by-layer charged polymer assembly approach that can be used to effectively recover the damaged crystals. It is shown that in addition to being an effective means for reasonable restoration of their optical waveguiding ability, this approach can also be used to combine different crystals into hybrid organic photonic integrated circuits (OPICs) and even to construct dynamic hybrid OPICs as active and/or passive optical waveguides. The resulting integrated crystalline OPIC bundles act as optical waveguides for transmission of light with different colors and can also be used for light mixing to generate white light.

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Fluorescence-based thermal sensing with elastic organic crystals

2022, Li, Liang, Di, Qi, Miao, Xiaodan, Lan, Linfeng, Yu, Xu, Liu, Bin, Yi, Yuanping, Naumov, Panče, Zhang, Hongyu

Operation of temperature sensors over extended temperature ranges, and particularly in extreme conditions, poses challenges with both the mechanical integrity of the sensing material and the operational range of the sensor. With an emissive bendable organic crystalline material, here we propose that organic crystals can be used as mechanically robust and compliant fluorescence-based thermal sensors with wide range of temperature coverage and complete retention of mechanical elasticity. The exemplary material described remains elastically bendable and shows highly linear correlation with the emission wavelength and intensity between 77 K to 277 K, while it also transduces its own fluorescence in active waveguiding mode. This universal new approach expands the materials available for optical thermal sensing to a vast number of organic crystals as a new class of engineering materials and opens opportunities for the design of lightweight, organic fluorescence-based thermal sensors that can operate under extreme temperature conditions such as are the ones that will be encountered in future space exploration missions.

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Organic Crystalline Optical Waveguides That Remain Elastic from -196 to ≈ 200°C

2022, Li, Liang, Tang, Shiyue, Ye, Kaiqi, Commins, Patrick, Naumov, Panče, Zhang, Hongyu

Organic crystals that are capable to deform (reversibly or irreversibly) similar to polymer materials have been widely reported over the past ten years. However, most of the reported organic crystals can only be elastically bent within a narrow temperature range, and reports on their thermal behavior that would encourage applications of these energy-transducing elements in extreme conditions are not readily available. This work designs a linear and flat π-conjugated molecule with double intramolecular hydrogen bonds that prevent thermally induced conformational distortions. The molecule assembles as a rigid building block into centimeter-sized wide organic crystals that can be elastically bent over a temperature range spanning close to 400 °C, from −196 to ≈200 °C. The emission wavelength of the crystals is also temperature dependent, and can be continually tuned from 547 to 577 nm upon heating from 20 to ≈200 °C. This inspires the design of a lightweight, organic, elastic optical waveguide where the output energy is controlled by the operating temperature. The wide range of crystal flexibility expands the range of conditions for application of organic crystals as optical waveguides.