Themed collection Molecular Crystals: Mechanics and Photonics

Focusing on the mechanics and photonics of molecular crystals, Rajadurai Chandrasekar, Panče Naumov, Xue-Dong Wang and Kristin Hutchins introduce a themed collection showcasing a series of articles that delve into their structural properties and broad range of functional applications.

This review shows how molecular aggregation enables emergent photophysics (RTP, radical emission, NIR luminescence, photothermal, X-ray scintillation) unseen in single molecules.

This review summarizes the organic stimuli-responsive tunable CPL materials based on various types of stimuli in recent years, focusing on the design principles, performance modulation mechanisms and potential applications.

Halide hybrid perovskite ferroelectrics can exist in bulk (single- or polycrystalline) and thin-film forms, exhibiting multifunctional properties suitable for applications in energy harvesting, sensing, and memory devices.

Tuning the optical band in flexible nano- and micro-crystalline structures using halogen atoms offers a promising route for fabricating functionally complex soft optical devices.

The thermal and thermomechanical behavior of multi-component organic solids is tuned at the molecular level via preparation of mixed cocrystals.

Pure color red emitting elastically flexible organic crystals with a pyrene core and showcasing active waveguiding properties were designed, and their potential for fabricating reconfigurable photonic integrated circuits was displayed.

This study presents a novel method for achieving as high as 6.7 wt% Er-doping in mesoporous silica via molecular engineering, yielding a unique 1640 nm photoluminescence, thus suitable for advanced photonic applications.

Disorder in cellulose hydrogen-bond networks activates distinct terahertz vibrations, enabling direct spectroscopic differentiation of subtle polymorphic structures.

High-pressure structural, spectroscopic and theoretical investigations towards understanding piezochromism of square-planar rhodium(I) dicarbonyl complexes exhibiting metallophilic interactions in a crystal are reported.

In this work, an experimental and theoretical investigation was carried out to explore the key factors influencing light transmission mechanisms in organic crystalline materials.

Using a dual inducing layer is a novel strategy for growing high-quality crystalline thin films via weak epitaxy growth. This work shows that a designed dual inducing layer can address critical hole injection challenges in crystalline OLEDs.

We designed and synthesized an n-type luminescent organic semiconductor, DPIDBSO. The symmetric silver electrode-based DPIDBSO OLET devices showed obvious n-type electroluminescence with a stationary emission zone.

Unique photo-switching in unusual low Z′-high Z′ co-crystal polymorphs is reported and studied to understand structure–property correlations through multi-stimuli-responsive and diffraction studies.

A mold-embedded growth method is presented for the batch production of organic scintillating single crystal fibers (SCFs). These SCFs can be integrated into a pixelated scintillator array, showing high performance in neutron detection.

DTBTE is a new fluorophore that exhibits luminescence changes due to transitions between crystalline and amorphous states. The combination of DFT calculations, X-ray analysis and advanced spectroscopy provided insights into this transformation.

Methylammonium lead iodide is widely used in the preparation of photodetectors because of its excellent photovoltaic properties.

Large-sized Cr³⁺-doped single crystal phosphors with enhanced near-infrared luminescence intensity and improved thermal stability relative to polycrystalline powders are successfully prepared via a room-temperature solvent exchange method.

We demonstrate a hybrid microcavity integrating a CsPbBr₃ superlattice with a thin Ag film to greatly enhance exciton–photon coupling and achieve continuous-wave-pumped polariton lasing with a low threshold of ∼220 W cm⁻².

Cocrystallization of odd–even aliphatic dicarboxylic acids with an organic fluorophore induces twist-elasticity, thus resulting odd–even effect in solid-state fluorescence as well as nanomechanical properties.

An effective design strategy for creating imidazo[1,2-a]pyridine-derived luminogens is proposed, offering a dependable avenue for building TADF-DSE materials for applications in OLEDs and cell imaging.

Beyond just finding different optical “characteristics”, we found “specific functions” for each polymorph due to the rational design of a polymorphic and highly luminescent compound.

The interaction between carriers and photons in halide perovskites gives rise to intriguing phenomena in their excited states.

An efficient broadband near-infrared Na₂CaTi₂Ge₃O₁₂:Cr³⁺ garnet phosphor with cationic disorder and charge self-balance achieves a high performance in near-infrared imaging.

Systematic substitution of Al³⁺ with Sc³⁺ modulates the crystal field environment around Cr³⁺, leading to enhanced luminescence efficiency while preserving anti-thermal quenching behavior at elevated temperatures.

Annealing LuPO₄:Pr³⁺ nanocrystals reduces local disorder and structural imperfections, enabling efficient energy transfer under deep high-energy excitation (45 eV photons), thereby enhancing UV-C luminescence for potential use in radiotherapy.

We conducted a detailed study of the quasi-skutterudite Ca₃Pt₄Sn₁₃ single crystal through measurements of electrical resistivity, Hall effect, specific heat, and thermoelectric properties.

An interfacial heteroepitaxy strategy was developed to fabricate molecularly thin, single-crystalline p–n heterojunctions with precise orientation control and their polarization-sensitive photodetection capabilities were explored.

We designed 2D elastic crystals based on asymmetric fluorinated donor–acceptor–donor molecular structures for hybridization with polyimide films, achieving 3D active optical waveguide properties.

OIMHs incorporating NDI cations exhibit flexible deformation under stress and function as mechanochromic and photothermal conversion materials, demonstrating their soft and multifunctional nature.

Replacing gallium with indium in the crystal structure of Ga₂O₃:Cr³⁺ redshifts the emission wavelength to 830 nm and induces persistent luminescence.

A novel chiral organic semiconductor (S)-4Br-PDI-Ph was synthesized and self-assembled into single-crystalline nanowires. Aniline surface vapor doping markedly improved their optoelectronic performance in phototransistors.

Heated (R/S-2-mpip)MnCl₄·2H₂O exhibited obvious the circular dichroism and circularly polarized luminescence.

Stimuli responsive fluorescent materials play an essential role in smart material engineering. We designed molecules that exhibited stimuli responsive luminescence and gradual proton release for the synthesis and passivation of metal nanoparticles.

Organic crystals integrate multicolor emissions from semiconductor quantum dots via a modular assembly approach. This modular strategy merges the advantages of quantum dots and organic crystals for versatile photonics.

The temperature of the thermosalient phase transition can be tuned within a range of 15 °C by varying the TBB content by 8% in the molecular TBB–TCB alloys.

New donor-carbazole-acceptor derivatives can exhibit fluorescence in the blue–orange spectral range. The observed emission suggests the involvement of through bond and through space charge transfers.

Photocyclization reactivity of inverse-type diarylethenes strongly depends on the dihedral angle in aryl groups. Especially, the photocyclization reaction in crystal requires a dihedral angle between the thiophene and phenyl rings greater than 81°.