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

• Published in: Advanced materials (Weinheim) Vol. 34; no. 11; pp. e2107169 - n/a
• Main Authors: Zhuo, Ming‐Peng, Yuan, Yi, Su, Yang, Chen, Song, Chen, Ye‐Tao, Feng, Zi‐Qi, Qu, Yang‐Kun, Li, Ming‐De, Li, Yang, Hu, Bing‐Wen, Wang, Xue‐Dong, Liao, Liang‐Sheng
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01.03.2022
• Subjects: Charge transfer; charge‐transfer interactions; Electron transitions; Excitons; Materials science; Near infrared radiation; near‐infrared emitters; Optical waveguides; organic cocrystals; Organic materials; Photoluminescence; photon transportation; Pitch (inclination); segregated stacking modes; Tetracyanoquinodimethane; organic cocrystals; photon transportation; near-infrared emitters; segregated stacking modes; charge-transfer interactions
• DOI: 10.1002/adma.202107169
• ISSN: 0935-9648; 1521-4095

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. Through changing mixed stacking into segregated stacking mode, triphenylene (TP)‐2,3,5,6‐tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane (F4TCNQ) charge‐transfer (CT) complex demonstrates a low CT degree and a small counter pitch angle between TP and F4TCNQ molecules, benefiting for breaking the forbidden electronic transitions of CT state for realizing the near‐infrared emission with a maximum peak of 770 nm and a photoluminescence quantum yield of 5.4%.