Segregated Array Tailoring Charge‐Transfer Degree of Organic Cocrystal for the Efficient Near‐Infrared Emission beyond 760 nm

Abstract

Harvesting the narrow bandgap excitons of charge‐transfer (CT) complexes for the achievement of near‐infrared (NIR) emission has attracted intensive attention for its fundamental importance and practical application. Herein, the triphenylene (TP)‐2,3,5,6‐tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane (F4TCNQ) CT organic complex is designed and fabricated via the supramolecular self‐assembly process, which demonstrates the NIR emission with a maximum peak of 770 nm and a photoluminescence quantum yield (PLQY) of 5.4%. The segregated stacking mode of TP‐F4TCNQ CT complex based on the multiple types of intermolecular interaction has a low CT degree of 0.00103 and a small counter pitch angle of 40° between F4TCNQ and TP molecules, which breaks the forbidden electronic transitions of CT state, resulting in the effective NIR emission. Acting as the promising candidates for the active optical waveguide in the NIR region beyond 760 nm, the self‐assembled TP‐F4TCNQ single‐crystalline organic microwires display an ultralow optical‐loss coefficient of 0.060 dB µm−1. This work holds considerable insights for the exploration of novel NIR‐emissive organic materials via an universal “cocrystal engineering” strategy.

Recent Progress of Novel Organic Near‐Infrared‐Emitting Materials

“…[ 73 ] Inspired by these advantages, our group skillfully developed a unique cocrystal strategy to finely self‐assemble the organic CT cocrystal with NIR emission via the noncovalent interaction of CT interaction, which is different from the above four kinds of NIR materials via the rational molecular design and advanced synthetic technique. [ 52 ] Moreover, the organic CT cocrystal of TP–F 4 TCNQ has been applied in NIR optical waveguides with a low optical loss coefficient ( R ) of 0.060 dB/μm at 770 nm. [ 52 ] This prospective investigation provides a deeper insight into the development of organic NIR emitters for advanced organic optoelectronics or multichannel bioimaging.…”

“…[ 52 ] Moreover, the organic CT cocrystal of TP–F 4 TCNQ has been applied in NIR optical waveguides with a low optical loss coefficient ( R ) of 0.060 dB/μm at 770 nm. [ 52 ] This prospective investigation provides a deeper insight into the development of organic NIR emitters for advanced organic optoelectronics or multichannel bioimaging.…”

“…[ 51 ] Drawing inspiration from this point, our group first applied the rational modulation of the molecular packing modes to tailor the photophysical properties of organic CT cocrystals, realizing the desired NIR emitters. [ 52 ] As given in Figure a, the CT interaction promotes the convention of F 4 TCNQ molecular structure from the neutral quinonoid form state to aromatic form state after accepting an electron, generating an electronic coupling and a narrow energy gap for longer wavelength of absorption or emission. In addition, strong CT interaction is desired for increased radical concentration, resulting in fluorescence quenching.…”

3D Optical Heterostructure Patterning by Spatially Allocating Nanoblocks on a Printed Matrix

“…As an important form of heterostructure application, optical heterostructure patterning with microscale or nanoscale materials has attracted immense attention in material science − and plays a key role in a variety of fields including display, , coding, , anticounterfeiting, , optical multiplexing, , and multiwavelength lasers. , In addition to size, composition, and morphology of the material, the spatial arrangement of the component units has a great influence on the property and function of the optical heterostructures. − Thus, various nanofabrication technologies, such as optical tweezers, , high-precision deposition, , lithography, , and field control, , have been applied to arrange the micro- and nanomaterials into morphology-controlled optical heterostructures. However, these techniques often suffer from the disadvantages of expensive instruments, complex processes, and limited materials, which largely restrict the large-area preparation and extensive application of the optical heterostructure.…”

A radical photochromic metal–organic framework for boosting NIR-II photothermal conversion and therapy

“…10 We have developed several photo-induced bistable photochromic MOFs (pMOF) based on the D-A system, 11,12 whose mechanism is analogous to the organic co-crystal photothermal strategy. 8,13,14 In general, the colour change of pMOF upon UV irradiation tends to display a large red-shift absorption in the visible or NIR region, which implies intermolecular CT interaction. Meanwhile, Yin and co-workers reported the first example of a MOF as a NIR photothermal material containing stable perylenediimide radical anions.…”