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Photoconstruction of a Microrelief in a Photochromic Crystalline Spirooxazine Film
摘要： In its crystalline form, spirooxazine does not usually exhibit photochromism. However, a crystalline spherulite spirooxazine film has been found to exhibit coloration upon irradiation with a continuous ultraviolet (UV) light and decoloration under the dark condition at room temperature, thereby indicating the occurrence of photochromism. The replicable microreliefs was construction of different successfully achieved by alternately irradiating with patterned UV light and heating the film to its melting point.
关键词： Spirooxazine,Surface relief,Spherulite
更新于2025-09-23 15:21:01
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Controlling Homogenous Spherulitic Crystallization for High‐Efficiency Planar Perovskite Solar Cells Fabricated under Ambient High‐Humidity Conditions
摘要： The influence of precursor solution properties, fabrication environment, and antisolvent properties on the microstructural evolution of perovskite films is reported. First, the impact of fabrication environment on the morphology of methyl ammonium lead iodide (MAPbI3) perovskite films with various Lewis-base additives is reported. Second, the influence of antisolvent properties on perovskite film microstructure is investigated using antisolvents ranging from nonpolar heptane to highly polar water. This study shows an ambient environment that accelerates crystal growth at the expense of nucleation and introduces anisotropies in crystal morphology. The use of antisolvents enhances nucleation but also influences ambient moisture interaction with the precursor solution, resulting in different crystal morphology (shape, size, dispersity) in different antisolvents. Crystal morphology, in turn, dictates film quality. A homogenous spherulitic crystallization results in pinhole-free films with similar microstructure irrespective of processing environment. This study further demonstrates propyl acetate, an environmentally benign antisolvent, which can induce spherulitic crystallization under ambient environment (52% relative humidity, 25 °C). With this, planar perovskite solar cells with ≈17.78% stabilized power conversion efficiency are achieved. Finally, a simple precipitation test and in situ crystallization imaging under an optical microscope that can enable a facile a priori screening of antisolvents is shown.
关键词： perovskite,spherulite,planar,crystallization,ambient
更新于2025-09-19 17:13:59
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Organization of Twisting Lamellar Crystals in Birefringent Banded Polymer Spherulites: A Mini-Review
摘要： In this mini-review, we summarize the evidences of lamellar twisting in the birefringent banded polymer spherulites demonstrated by various characterization techniques, such as polarized optical microscopy, real-time atomic force microscopy, micro-focus wide angle X-ray diffraction, etc. The real-time observation of lamellar growth under atomic force microscopy unveiled the fine details of lamellar twisting and branching in the banded spherulites of poly(R-3-hydroxybutyrate-co-17 mol % R-3-hydroxyhexanoate). Organization of the twisting lamellar crystals in the banded spherulites was revealed as well. The lamellar crystals change the orientation via twisting rather than the macro screw dislocations. In fact, macro screw dislocation provides the mechanism of synchronous twisting of neighboring lamellar crystals. The driving force of lamellar twisting is attributed to the anisotropic and unbalanced surface stresses. Besides molecular chirality, variation of the growth axis and the chemical groups on lamellar surface can change the distribution of the surface stresses, and thus may invert the handedness of lamellar twisting. Thus, based on both experimental results and physical reasoning, the relation between crystal chirality and chemical molecular structures has been suggested, via the bridge of the distribution of surface stresses. The factors affecting band spacing are briefly discussed. Some remaining questions and the perspective of the topic are highlighted.
关键词： banded polymer spherulite,chirality,ringed spherulite,organization of lamellar crystals,surface stresses,lamellar twisting
更新于2025-09-04 15:30:14