Now showing 1 - 6 of 6
  • Publication
    Ionic Liquid Engineering in Perovskite Photovoltaics
    ( 2022) ;
    Wang, Fei
    ;
    Duan, Dawei
    ;
    Singh, Mriganka
    ;
    Sutter‐Fella, Carolin M
    ;
    Lin, Haoran
    ;
    Naumov, Panče
    ;
    Hu, Hanlin
    Over the past decade, perovskite photovoltaics have approached other currently available technologies and proven to be the most prospective type of solar cells. Although the many-sided research in this very active field has generated consistent results with regards to their undisputed consistently increasing power conversion efficiency, it also produced several rather contradictory opinions. Among other important details, debate surrounding their proneness to surface degradation and poor mechanical robustness, as well as the environmental footprint of this materials class remains a moot point. The application of ionic liquids appears as one of the potential remedies to some of these challenges due to their high conductivity, the opportunities for chemical ‘tuning’ of the structure, and relatively lower environmental footprint. This article provides an overview, classification, and applications of ionic liquids in perovskite solar cells. We summarize the use and role of ionic liquids as versatile additives, solvents, and modifiers in perovskite precursor solution, charge transport layer, as well as for interfacial and stability engineering. Finally, challenges and the future prospects for the design and/or selection of ionic liquids with a specific profile that meets the requirements for next generation highly efficient and stable perovskite solar cells are proposed.
      64Scopus© Citations 1
  • Publication
    Packing-Dependent Mechanical Properties of Schiff Base Crystals
    ( 2022) ;
    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.
      6
  • Publication
    Recent Progress in Ionic Liquids for Stability Engineering of Perovskite Solar Cells
    ( 2022) ;
    Wang, Fei
    ;
    Ge, Chuang-ye
    ;
    Duan, Dawei
    ;
    Lin, Haoran
    ;
    Naumov, Panče
    ;
    Hu, Hanlin
    Perovskite solar cells attract widespread attention due to their impressive power conversion efficiencies, high absorption coefficients, tunable bandgap, and straightforward manufacturing protocols. However, in the process of further development and optimization toward mass production, the long-term stability stands as one of the most urgent challenges that need to be overcome. Given the excellent thermal stability and high structural designability, ionic liquids (ILs) are relatively green room-temperature molten salts that have been widely applied to perovskite photovoltaic devices with promising results in view of improved stability and enhanced device performance. In this review, the reasons and mechanisms of instability of such devices under external and internal factors are analyzed. The current strategies of ILs engineering for improved stability of the devices are classified and summarized, including the IL-assisted perovskite film evolution and IL-modified photophysical properties of the perovskite photoactive layer and the related stability and photovoltaic performance of the devices. The challenges that stand as obstacles toward further development of perovskite solar cells based on IL engineering and their prospects are also discussed.
      8
  • Publication
    Remote and precise control over morphology and motion of organic crystals by using magnetic field
    ( 2022) ;
    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.
    Scopus© Citations 2  10  1
  • Publication
    A Low-Temperature-Resistant Flexible Organic Crystal with Circularly Polarized Luminescence
    ( 2022) ;
    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.
    Scopus© Citations 1  16  4
  • Publication
    Organic Crystalline Optical Waveguides That Remain Elastic from -196 to ≈ 200°C
    ( 2022) ;
    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.
      8