Energy Conversion in Single‐Crystal‐to‐Single‐Crystal Phase Transition Materials

Abstract

Single‐crystal‐to‐single‐crystal (SCSC) phase transitions are direct structural evolutions of crystalline materials in the solid state without the damage of ordering in the crystal lattice. These multidimensional SCSC phase transition materials are responsive to multiple external stimuli (heat, light, mechanical force, electricity, etc.), and have therefore demonstrated promising applications in many fields such as sensors, actuators, artificial muscles, soft robotics, and energy harvesting. The directionality and cooperativity of intermolecular interactions in crystal structures together with a sustained and long‐range dynamics, and the fact that they can operate at high frequency, enable fast and efficient energy conversion processes in SCSC phase transition materials. In this review, the SCSC phase transition materials are analyzed by dividing them into different types of energy transformation, from the point of view of different stimuli that initiate and drive the phase transition, including the thermo‐, photo‐, electric‐, and mechanic‐induced energy transformation, and the dimensionality dependent characteristics in these processes are presented. Moreover, the state‐of‐the‐art design and fabrication of the SCSC phase transition materials as well as the mechanisms of their energy conversion processes are discussed. Finally, the challenges and future potentials are also discussed.

Exceptionally high work density of a ferroelectric dynamic organic crystal around room temperature

“…Molecular crystals comprise an emerging class of materials that contribute to the engineering materials’ toolbox structures that are endowed with mechanical softness, long-range structural order, and anisotropy in their physical properties 1 – 4 . At much lower density than many other engineering materials, the weak intermolecular interactions in organic crystals can effectively absorb elastic energy that had accumulated as a result of the development of mechanical strain, thereby effectively expanding their plastic regime.…”

Shape-stabilized phase change composites enabled by lightweight and bio-inspired interconnecting carbon aerogels for efficient energy storage and photo-thermal conversion

“…1,2 Phase change materials (PCMs) are promising for thermal energy storage and have been widely studied due to their high-efficiency energystorage capabilities and constant phase-change temperatures. 3,4 Therefore, PCMs have been broadly implemented in the thermal energy storage and temperature control elds. [5][6][7] As popular energy-storage materials, organic PCMs such as polyethylene glycol (PEG), which exhibit excellent thermal storage performance and good chemical stability, offer good prospects for photo-thermal conversion, and thermal management in electronic devices.…”

“…1,2 Phase change materials (PCMs) are promising for thermal energy storage and have been widely studied due to their high-efficiency energy-storage capabilities and constant phase-change temperatures. 3,4 Therefore, PCMs have been broadly implemented in the thermal energy storage and temperature control fields. 5–7…”

Mechanical twinning in organic crystals

“…20 As a side note, there is another kind of mechanically induced martensitic transition: a polymorphic transition, which can drastically change the shapes 21–29 and/or functions of crystals 30–35 and has been reviewed recently. 20,36 In addition to morphological and functional aspects, strain-independent deformation stress in mechanical twinning due to cooperative molecular movements is also noteworthy. These characteristics differentiate a diffusionless plastic deformation by mechanical twinning from elastic deformation by elastic lattice strains and from plastic deformation by molecular diffusion (Fig.…”