A cocrystal strategy with a simple preparation process is developed to prepare novel materials for near‐infrared photothermal (PT) conversion and imaging. DBTTF and TCNB are selected as electron ...donor (D) and electron acceptor (A) to self‐assemble into new cocrystals through non‐covalent interactions. The strong D–A interaction leads to a narrow band gap with NIR absorption and that both the ground state and lowest‐lying excited state are charge transfer states. Under the NIR laser illumination, the temperature of the cocrystal sharply increases in a short time with high PT conversion efficiency (η=18.8 %), which is due to the active non‐radiative pathways and inhibition of radiative transition process, as revealed by femtosecond transient absorption spectroscopy. This is the first PT conversion cocrystal, which not only provides insights for the development of novel PT materials, but also paves the way of designing functional materials with appealing applications.
The heat is on: A new cocrystal with NIR photothermal properties is prepared from two small molecules, wherein the strong charge‐transfer interaction leads to active non‐radiative pathways, as revealed by femtosecond transient absorption spectroscopy.
The spectroscopic and photophysical properties of organic materials in the solid‐state are widely accepted as a result of their molecular packing structure and intermolecular interactions, such as J‐ ...and H‐aggregation, charge‐transfer (CT), excimer and exciplex. However, in this work, we show that Spe‐F4DIB cocrystals (SFCs) surprisingly retain the energy levels of photoluminescence (PL) states of Spe crystals, despite a significantly altered molecular packing structure after cocrystallization. In comparison, Npe‐F4DIB cocrystals (NFCs) with new spectroscopic states display different spectra and photophysical behaviors as compared with those of individual component crystals. These may be related to the molecular configuration in crystals, and we propose Spe as an “intramolecular emissive” material, thus providing a new viewpoint on light‐emitting species of organic chromophores. Moreover, the nonlinear optical (NLO) properties of Npe and Spe are firstly demonstrated and modulated by cocrystallization. The established “molecule‐packing‐property” relationship helps to rationally control the optical properties of organic materials through cocrystallization.
Luminescent halogen‐bonded solids: Two new halogen‐bonded cocrystals were prepared and characterized for their crystal structure, self‐assembling manner, spectroscopic, photophysical, and nonlinear optical properties. The molecule‐packing‐property relationship helps to rationally design and prepare cocrystals with desired properties.
Charge-transfer (CT) interactions between donor (D) and acceptor (A) groups, as well as CT exciton dynamics, play important roles in optoelectronic devices, such as organic solar cells, ...photodetectors, and light-emitting sources, which are not yet well understood. In this contribution, the self-assembly behavior, molecular stacking structure, CT interactions, density functional theory (DFT) calculations, and corresponding physicochemical properties of two similar halogen-bonded co-crystals are comprehensively investigated and compared, to construct an "assembly-structure-CT-property" relationship. Bpe-IFB wire-like crystals (where Bpe = 1,2-bis(4-pyridyl)ethylene and IFB = 1,3,5-trifluoro-2,4,6-triiodobenzene), packed in a segregated stacking form with CT ground and excited states, are measured to be quasi-one-dimensional (1D) semiconductors and show strong violet-blue photoluminescence (PL) from the lowest CT1 excitons (ΦPL = 26.1%), which can be confined and propagate oppositely along the 1D axial direction. In comparison, Bpe-F4DIB block-like crystals (F4DIB = 1,4-diiodotetrafluorobenzene), packed in a mixed stacking form without CT interactions, are determined to be insulators and exhibit unique white light emission and two-dimensional optical waveguide property. Surprisingly, it seems that the intrinsic spectroscopic states of Bpe and F4DIB do not change after co-crystallization, which is also confirmed by theoretical calculations, thus offering a new design principle for white light emitting materials. More importantly, we show that the CT interactions in co-crystals are related to their molecular packing and can be triggered or suppressed by crystal engineering, which eventually leads to distinct optoelectronic properties. These results help us to rationally control the CT interactions in organic D-A systems by tuning the molecular stacking, toward the development of a fantastic "optoelectronic world".
Cocrystals of 4‐styrylpyridine and 1,2,4,5‐tetracyanobenzene were successfully prepared by supramolecular self‐assembly. Donor–acceptor interactions between the molecular components are the main ...driving force for self‐assembly and contribute to intermolecular charge transfer. The cocrystals possess two‐photon absorption properties that are not observed in the individual components; suggesting that two‐photon absorption originates from intermolecular charge‐transfer interactions in the donor–acceptor system. The origin of two‐photon absorption in multichromophore systems remains under‐researched; thus, the system offers a rare demonstration of two‐photon absorption by cocrystallization. Cocrystal engineering may facilitate further design and development of novel materials for nonlinear optical and optoelectronic applications.
Finding light in the darkness: Cocrystals comprising 4‐styrylpyridine and 1,2,4,5‐tetracyanobenzene (STC) display two‐photon absorption. Intermolecular charge‐transfer interactions between the molecular components of the supramolecular assembly facilitate two‐photon absorption that is absent from the individual molecules.
A new crystal of a charge‐transfer (CT) complex was prepared through supramolecular assembly and it has unique two‐dimensional (2D) morphology. The CT nature of the ground and excited states of this ...new Bpe‐TCNB cocrystal (BTC) were confirmed by electron spin resonance measurements, spectroscopic studies, and theoretical calculations, thus providing a comprehensive understanding of the CT interactions in organic donor–acceptor systems. And the lowest CT1 excitons are responsible for the efficient photoluminescence (ΦPL=19 %), which can actively propagate in individual 2D BTCs without anisotropy, thus implying that the optical waveguide property of the crystal is not related to the molecular stacking structure. This unique 2D CT cocrystal exhibits potential for use in functional photonic devices in the next‐generation optoelectronic communications.
Crystal clear: A new crystal of a donor–acceptor (D–A) complex was prepared and it has a two‐dimensional morphology. The charge‐transfer interactions were fully investigated. This organic cocrystal has unique two‐dimensional optical waveguide properties, and has potential applications in next‐generation optoelectronic communications.
As the variety of space targets expands, two-dimensional (2D) ISAR images prove insufficient for target recognition, necessitating the extraction of three-dimensional (3D) information. The 3D ...geometry reconstruction method utilizing energy accumulation of ISAR image sequence (ISEA) facilitates superior reconstruction while circumventing the laborious steps associated with factorization methods. Nevertheless, ISEA’s neglect of valid information necessitates a high quantity of images and elongated operation times. This paper introduces a partitioned parallel 3D reconstruction method utilizing sorted-energy semi-accumulation with ISAR image sequences (PP-ISEA) to address these limitations. The PP-ISEA innovatively incorporates a two-step search pattern—coarse and fine—that enhances search efficiency and conserves computational resources. It introduces a novel objective function ‘sorted-energy semi-accumulation’ to discern genuine scatterers from spurious ones and establishes a redundant point exclusion module. Experiments on the scatterer model and simulated electromagnetic model demonstrate that the PP-ISEA reduces the minimum image requirement from ten to four for high-quality scatterer model reconstruction, thereby offering superior reconstruction quality in less time.
The charge transfer and photophysics in a new light‐emitting cocrystal with ribbon‐like morphology are revealed in‐depth. These cocrystals can serve as an efficient 1D optical waveguide, and the ...cocrystal waveguide couplers fabricated by a probe‐assisted crystal‐moving technique exhibit interfacial white emission and can function as basic photonic logic gates, showing potential for future integrated photonics.
Organic semiconductor materials are considered to be promising photocatalysts due to their excellent light absorption by chromophores, easy molecular structure tuning, and solution‐processable ...properties. In particular, donor‐acceptor (D‐A) type organic photocatalytic materials synthesized by introducing D and A units intra‐ or intermolecularly, have made great progress in photocatalytic studies. More and more studies have demonstrated that the D‐A type organic photocatalytic materials combine effective carrier separation, tunable bandgap, and sensitive optoelectronic response, and are considered to be an effective strategy for enhancing light absorption, improving exciton dissociation, and optimizing carrier transport. This review provides a thorough overview of D‐A strategies aimed at optimizing the photocatalytic performance of organic semiconductors. Initially, essential methods for modifying organic photocatalytic materials, such as interface engineering, crystal engineering, and interaction modulation, are briefly discussed. Subsequently, the review delves into various organic photocatalytic materials based on intramolecular and intermolecular D‐A interactions, encompassing small molecules, conjugated polymers, crystalline polymers, supramolecules, and organic heterojunctions. Meanwhile, the energy band structures, exciton dynamics, and redox‐active sites of D‐A type organic photocatalytic materials under different bonding modes are discussed. Finally, the review highlights the advanced applications of organic photocatalystsand outlines prospective challenges and opportunities.
This review highlights recent advances in the field of donor‐acceptor (D‐A) organic photocatalysis. It covers a wide range of subjects, from intramolecular and intermolecular D‐A interactions between building blocks at the microscopic level to macroscopic functional applications. This review can serve as a comprehensive understanding of the design of next‐generation D‐A organic photocatalysts.
Perovskite solar cells (PSCs) have advanced rapidly with power conversion efficiencies (PCEs) now exceeding 22%. Due to the long diffusion lengths of charge carriers in the photoactive layer, a PSC ...device architecture comprising an electron‐ transporting layer (ETL) is essential to optimize charge flow and collection for maximum performance. Here, a novel approach is reported to low temperature, solution‐processed ZnO ETLs for PSCs using combustion synthesis. Due to the intrinsic passivation effects, high crystallinity, matched energy levels, ideal surface topography, and good chemical compatibility with the perovskite layer, this combustion‐derived ZnO enables PCEs approaching 17–20% for three types of perovskite materials systems with no need for ETL doping or surface functionalization.
An effective approach to low temperature, solution‐processed ZnO electron‐transport layers (ETLs) for perovskite solar cells by combustion synthesis is developed. Due to the intrinsic passivation effects, high crystallinity, matched energy levels, ideal surface topography, and good chemical compatibility with the perovskite layer, combustion‐processed ZnO electron transport layers enable power conversion efficiencies approaching 17–20% for three representative perovskite systems without ETL doping or surface functionalization.
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