Two-Dimensional Organic Single Crystals with Scale Regulated, Phase-Switchable, Polymorphism-Dependent, and Amplified Spontaneous Emission Properties

Abstract

The successful preparation of two-dimensional (2D) single crystals can promote the development of organic optoelectronic devices with excellent performance. A Schiff base compound salicylidene(4-dimethylamino)aniline with aggregation induced emission (AIE) property was employed as the building block to fabricate 2D thin single crystal plates with scales from around 50 μm to 1.5 cm. Yellow and red emissive polymorphs were concomitantly obtained during crystallization. The single-crystal-to-single-crystal (SC-to-SC) transformation from yellow polymorph to red one was demonstrated. Furthermore, both polymorphs exhibited amplified spontaneous emission (ASE) properties. Interestingly, the red polymorph displayed size-dependent ASE characteristics. The larger red polymorph showed near-infrared ASE with maximum at 706 nm, whereas the smaller one presented red ASE with maximum at 610 nm. These results suggest that the different scale single crystalline thin films with perfect optoelectronic properties may be fabricated by using the organic molecules with 2D assembly feature.

Organic Cocrystals: Beyond Electrical Conductivities and Field‐Effect Transistors (FETs)

“…Organic crystals with distinctive shapes and smooth crystal planes can be used as active optical waveguide resonators, which provides a novel platform for optical confinement . Compared with 1D organic crystals, 2D crystals can transfer photons along different directions, making them much more suitable for applications in optical planar diodes, a whispering‐gallery‐mode (WGM) resonator including controlling directional waveguides and organic crystal lasing . However, very few organic molecules present 2D self‐assembly behaviors for a single component material, greatly impeding the development of 2D organic photonics and electronics .…”

Reversible Crystal‐to‐Crystal Phase Transitions with High‐Contrast Luminescent Alterations for a Thermally Activated Delayed Fluorescence Emitter

“…These results also demonstrated that crystal‐Y and crystal‐R belonged to thermally and kinetically stable states, respectively. [ 23 ]…”

“…These results also demonstrated that crystal-Y and crystal-R belonged to thermally and kinetically stable states, respectively. [23] It has been proven that the stimuli-induced luminescence switching of organic materials depend heavily on the molecular packing structures such as molecular conformations and intermolecular interactions. [24] To illustrate the relationship between the crystal-to-crystal phase transitions and molecular packing structures, single crystal XRD analyses were conducted and the detailed crystallographic data were summarized in Table S2, Supporting Information.…”

Highly Elastic Organic Crystals for Flexible Optical Waveguides

“…In our exploration of functionalized EOSCs, we attempted the use of a Shiff base, ( E )‐1‐(4‐(dimethylamino)phenyl)iminomethyl‐2‐hydroxyl‐naphthalene (DPIN in Figure a). The formation of intramolecular hydrogen bond between the OH and CH=N groups is expected because similar interactions have been commonly observed in the crystal structures of analogs compounds . The hydrogen bond should result in a relatively planar conjugated skeleton for π‐stacking.…”

“…Thef ormation of intramolecular hydrogen bond between the OH and CH = Ng roups is expected because similar interactions have been commonly observed in the crystal structures of analogs compounds. [13] Theh ydrogen bond should result in arelatively planar conjugated skeleton for p-stacking. It was found that brightly fluorescent ultralong EOSCs which are highly bendable under external stress can be prepared using DPIN (Figures 1b,c By layering hexane on the top of aCH 2 Cl 2 solution (0.1m) of DPIN and subsequent solvent diffusion, ultra-long rod-like single crystals were easily obtained.…”