Cryogenically Flexible Phosphorescent Organic Crystals that Transmit Self-Sustained Persistent Luminescence with Spatiotemporal Control.

Concomitant long-lived phosphorescence and cryogenic elasticity in soft matter is an immensely challenging endeavor due to the contrasting effect of low temperatures on these properties. While the low temperature normally extends and enhances phosphorescence, it typically compromises mechanical elasticity by freezing the molecular motion, inevitably leading to brittleness and cracking of soft materials. In this work, we posit that the emerging class of organic crystals can overcome this intrinsic disparity and describe an organic crystalline material that meets both requirements─an exceptional elasticity of its crystals at 77 K and ultralong afterglow of up to about 30 s, the longest lifetime of a flexible organic crystal reported to date.

Elastic circular organic microcrystals prepared by photoinduced delamination.

Circular organic crystals are essential as optically transducive components in flexible organic optoelectronics, yet this crystal habit is not easily obtained through traditional crystallization approaches. Here, we present a photoresponsive organic crystalline material that when exposed to ultraviolet or visible light, initially undergoes photoinduced bending, followed by photosalient effect and accompanied by delamination to elastic quasicircular microcrystals. Curvature analysis under different conditions confirms the controllability of this process.

PTAA-Based Perovskite Photovoltaics Catching up: Ionic Liquid Engineering-Assisted Crystallization Through Sequential Deposition.

PTAA as a widely studied polymeric hole transporting material, has garnered significant attention due to its outstanding thermal and chemical stability. However, the performance of PTAA-based p-i-n devices is shown to lag behind counterpart utilizing oxides or SAMs. In this study, the ionic liquid, 1-ethyl-3-methylimidazolium formate (EMIMCOOH), is innovatively introduced into the lead iodide (PbI) precursor solution, resulting in a more pronounced mesoporous PbI film with expended pore-size and denser pores.

Ultra-Wide Modulation and Reversible Reconfiguration of a Flexible Organic Crystalline Optical Waveguide Between 645 and 731 nm.

Flexible organic crystalline optical waveguides, which deliver input or self-emit light through various dynamic organic crystals, have attracted increasing attention in the past decade. However, the modulation of the waveguide output relies on chemical design and substituent modification, being time-consuming and laborious. Here we report an elastic organic crystal that displays long-distance light transduction up to 2.

Elastic Organic Crystals Exhibiting Amplified Spontaneous Emission Waveguides with Standard Red Chromaticity of the Rec.2020 Gamut.

The use of mechanically flexible molecular crystals as optical transuding media is demonstrated for a plethora of applications; however, the spectral peaks of optical outputs located mainly in the range of 400-600 nm are insufficient for practical telecommunication and full-color display applications. Herein, two elastically bendable organic crystals are reported that show red emission of the rec.709 gamut under 365 nm UV light irradiation yet generate rec.

Hybrid Elastic Organic Crystals that Respond to Aerial Humidity.

Reshaping of elongated organic crystals that can be used as semiconductors, waveguides or soft robotic grippers by application of force or light is now a commonplace, however mechanical response of organic crystals to changes in humidity has not been accomplished yet. Here, we report a universal approach to instigating a humidity response into elastically bendable organic crystals that elicits controllable deformation with linear response to aerial humidity while retaining their physical integrity entirely intact. Hygroresponsive bilayer elements are designed by mechanically coupling a humidity-responsive polymer with elastic molecular crystals that have been mechanically reinforced by a polymer coating.

Quantifiable stretching-induced fluorescence shifts of an elastically bendable and plastically twistable organic crystal.

Organic crystals with mechanical stimulus-response properties are being developed increasingly nowadays. However, the studies involving tensile-responsive crystals are still lacking due to the strict requirement of crystals with good flexibility. In this work, an organic crystal with the ability of elastic bending and plastic twisting upon loading stress and shearing force, respectively, is reported.

Self-Waveguide Single-Benzene Organic Crystal with Ultralow-Temperature Elasticity as a Potential Flexible Material.

With the increasing popularity and burgeoning progress of space technology, the development of ultralow-temperature flexible functional materials is a great challenge. Herein, we report a highly emissive organic crystal combining ultralow-temperature elasticity and self-waveguide properties (when a crystal is excited, it emits light from itself, which travels through the crystal to the other end) based on a simple single-benzene emitter. This crystal displayed excellent elastic bending ability in liquid nitrogen (LN).

Engineering Mechanical Compliance of an Organic Compound toward Flexible Crystal Lasing Media.

Recently, organic crystals with mechanical flexibility have been emerging as a hot research topic due to their great potentials in flexible optoelectronics. However, organic crystals exhibiting elastic bending or plastic bending are relatively rare. In this study, we proposed a strategy to improve the probability of crystal flexibility as well as to regulate the mechanical properties by controlling polymorphism.

A Flexible Organic Single Crystal with Plastic-Twisting and Elastic-Bending Capabilities and Polarization-Rotation Function.

Flexible organic single crystals capable of plastic or elastic deformations have a variety of potential applications. Although the integration of plasticity and elasticity in a crystal is theoretically possible and it may cause rich and complex deformations which are highly demanded for potential applications, the integration is hard to realize in practice. Here, we show that through utilizing different modes of external forces for influencing molecular packing in different crystallographic directions, plastic helical twisting and elastic bending can both be achieved for a crystal, and they can even be realized simultaneously.

Efficient Red-Emissive Organic Crystals with Amplified Spontaneous Emissions Based on a Single Benzene Framework.

Red-emissive fluorophores generally consist of large π-extended systems and thus encounter the problem of serious fluorescence quenching in the solid state. A series of structurally simple compounds 2,5-bis(alkylamino)terephthalates 1 a-c are reported that consist of a very small π-system (only a single benzene) but display efficient red emission in crystals. Crystal 1 a having a molecular weight of only 252 g mol shows red emission with the maximum of 620 nm and a fluorescence quantum yield of 0.

1,3-Diaryl-β-diketone Organic Crystals with Red Amplified Spontaneous Emission.

In this study, 1-[4-(dimethylamino)phenyl]-3-(1-hydroxynaphthalen-2-yl)propane-1,3-dione (DPHND) was designed and synthesized to construct red-emissive organic solids. Although DPHND was weakly yellow fluorescent in organic solvents, its emission intensity showed a significant enhancement when a relatively large amount of poor solvent was added, and displayed typical aggregation-induced enhanced emission (AIEE). Notably, the crystals formed by a solution-diffusion approach showed bright red fluorescence (λ =621 nm), which was greatly redshifted by about 60 nm compared with that in solution.

Highly efficient blue solid emitters and tautomerization-induced ON/OFF fluorescence switching based on structurally simple 3(5)-phenol-1H-pyrazoles.

3(5)-Phenyl-1H-pyrazoles are employed in this study to develop highly efficient organic crystalline solids with deep-blue ESIPT fluorescence as well as provide novel experimental insight into the mechanism of ESIPT fluorescence and generate an intriguing fluorescence "ON/OFF" switching.

Single-benzene solid emitters with lasing properties based on aggregation-induced emissions.

The very simple organic molecules have been employed to construct highly efficient single-benzene solid emitters (quantum yields: 0.72-0.84) with crystal lasing properties based on aggregation-induced emission (AIE) generated through an excited-state intramolecular proton transfer (ESIPT) reaction.