Single-photon upconversion in 6-pentaceneone crystal from bulk to ultrathin flakes

Multi-Mode Photoluminescence Regulation in a Zero-Dimensional Organic-Inorganic Hybrid Metal Halide Perovskite─[(CH3)4N]2SnCl6

Metal ion-doped zero-dimensional halide perovskites provide good platforms to generate broadband emission and explore the fundamental dynamics of emission regulations. Recently, Sb3+-doped zero-dimensional halide perovskites have attracted considerable attention for the high quantum yield of yellow emission; however, the triplet state recombination is activated and the singlet state emission is usually absent. Herein, we fabricate an Sb3+-doped zero-dimensional [(CH3)4N]2SnCl6 perovskite that can induce singlet and triplet emission. Density functional theory calculation shows that there are some overlaps between the highest occupied molecular orbitals and the lowest unoccupied molecular orbitals, which may induce a large energy separation between the lowest excited triplet states (T1) and the lowest excited singlet states (S1) [ΔE(S1 - T1)], impeding all the carriers' transfer from the singlet state to the triplet state. As a result, the reserved singlet emission together with the triplet emission can be regulated by excitation wavelength in situ. In addition, different Bi3+ ratios are co-doped into Sb3+@[(CH3)4N]2SnCl6, resulting in a photoluminescence ex situ regulation. Single-phase white light LED and optical anti-counterfeiting are developed further.

The competitive role of C–H⋯X (X = F, O) and π–π interactions in contributing to the degree of charge transfer in organic cocrystals: a case study of heteroatom-free donors with p-fluoranil (FA)

Four binary organic charge transfer cocrystals were grown by the slow cooling method. The competitive role of C–H⋯X (X = F, O) and π–π interactions in contributing to the degree of charge transfer in the cocrystals was investigated.

The moisture-responsive structural transformation of manganochlorine for water-soluble luminescent switching ink

CsMnCl3(H2O)2 (CMCH) has been widely investigated for magnetic and optical applications, including anti-Stokes photoluminescence, microwave absorption, and magnon-assisted optical transitions. Herein, CMCH crystals, which are colorless and transparent (unlike the pink crystals reported previously), were obtained through a unique approach. Consequently, a high-resolution optical absorption spectrum and distinct thermal behavior were observed. The reversible (de)hydration of CMCH being accompanied by photoluminescence switching (mainly in terms of the color temperature) was rationalized using crystal structure analysis. As a result, water-soluble CMCH could be applied as a moisture-responsive luminescent ink. Moreover, density functional theory (DFT) calculations were performed to understand the optical absorption of CMCH.

The Stoichiometry of TCNQ-Based Organic Charge-Transfer Cocrystals

Organic charge-transfer cocrystals (CTCs) have attracted significant research attention due to their wide range of potential applications in organic optoelectronic devices, organic magnetic devices, organic energy devices, pharmaceutical industry, etc. The physical properties of organic charge transfer cocrystals can be tuned not only by changing the donor and acceptor molecules, but also by varying the stoichiometry between the donor and the acceptor. However, the importance of the stoichiometry on tuning the properties of CTCs has still been underestimated. In this review, single-crystal growth methods of organic CTCs with different stoichiometries are first introduced, and their physical properties, including the degree of charge transfer, electrical conductivity, and field-effect mobility, are then discussed. Finally, a perspective of this research direction is provided to give the readers a general understanding of the concept.

Luminescent Polymorphic Co-crystals: A Promising Way to the Diversity of Molecular Assembly, Fluorescence Polarization, and Optical Waveguide

The design of molecular optoelectronic materials based on fabricating polymorphs and/or co-crystals has received much recent attention in the fields of luminescence, sensors, nonlinear optics, and so on. If the advantages of the two crystal engineering strategies above were combined, the diversity of self-assembly fashions and the tuning of photofunctional performances would be largely extended. However, such multicomponent examples have still been very limited to date. Herein, we report the construction of luminescent polymorphic co-crystals by assembly of tris(pentafluorophenyl)borane (TPFB) with 9,10-dicyanoanthracene (DCA) and acridine (AC) as paradigms. Different stacking modes and arrangement styles based on identical building block units in polymorphic co-crystals result in adjustable crystalline morphologies and variant photophysical properties (such as fluorescence wavelength, lifetimes, and up-conversion luminescence). The optimized photoluminescence quantum yield (63.1%) and lifetime (57.1 ns) are much higher than those of the pristine assembled units. In addition, two polymorphic co-crystals (DCA@TPFB-1 and AC@TPFB-2) present prominent fluorescence polarization and optical waveguide behaviors due to the highly regulated molecular orientation. Their high one-dimensional luminescence anisotropy (0.652) and low optical waveguide loss (0.0079 dB/μm) outperform most state-of-the-art low-dimensional molecular systems and thus endow them with great opportunities for photonic materials and devices. Therefore, this work not only confirms that constructing polymorphic co-crystals can be an effective way to design new photofunctional materials for luminescence and photonic applications but also discloses a deep understanding on the relationship between variant self-assembled fashions and tunable photofunctional properties of new TPFB-based molecular materials.