Cocrystal engineering—a clever way for designing multifunctional material

Cocrystal engineering is an ingenious strategy for assembling organic molecules through the non-covalent interaction force, avoiding harsh experimental conditions (i.e., high temperature and high pressure). By selecting the appropriate components, the donor-acceptor (D-A) molecules can be assembled like the jigsaw puzzle. Under the intermolecular interaction, such as π–π interactions, hydrogen bonds, and halogen bonds, cocrystal can not only display the intrinsic properties of its components but also show some novel properties, which can  realize the “1+1>2” effect. So cocrystal strategy has the advantage in designing multifunctional materials.

Researchers led by Prof. Xiaotao Zhang at Tianjin University, China, are devoted to designing multifunctional organic cocrystal material. They obtained a Flu-TCNQ cocrystal with integrated optoelectronic properties, which  is scarce because of the contradiction between the luminescent and electric properties of organic material. Many researchers have achieved the integration of photoelectric characteristics by introducing specific functional structures, but it is time-consuming and difficult to balance the two properties. In addition, most of the organic optoelectronic materials by this method exhibit a blue or green emission, and few materials exhibit red emission. And these optoelectronic materials mainly display p-type charge transport behavior. Zhang et al. selected the Flu (donor) as the luminescence unit due to its good luminescence, extended π-conjugated plans, and rich electrons properties. And they selected the TCNQ (acceptor) as the electrical building block, a typical n-type semiconductor that can provide a strong electron-withdrawing capacity. Both two compositions were easily obtained, avoiding the tedious synthetic routes. Driven by the charge transfer (CT) interaction and affected by the D-A molecules stacking mode, the emission of Flu-TCNQ cocrystal was regulated to be red, and the n-type charge transport property of the acceptor molecule was maintained in the cocrystal. Their work provides an effective solution to the shortage of organic materials with integrated optoelectronic properties.

The work entitled “TCNQ-based organic cocrystal integrated red emission and n-type charge transport” was published on Frontiers of Optoelectronics (May 9, 2022).

Notes: Flu: fluorine; TCNQ: 7,7′,8,8′-tetracyanoquinodimethane

Reference: Mengjia Jiang, Shuyu Li, Chun Zhen, Lingsong Wang, Fei Li, Yihan Zhang, Weibing Dong, Xiaotao Zhang, Wenping Hu. TCNQ-based organic cocrystal integrated red emission and n-type charge transport. Front. Optoelectron. 15, 21 (2022). https://doi.org/10.1007/s12200-022-00022-7

About Higher Education Press

Founded in May 1954, Higher Education Press Limited Company (HEP), affiliated with the Ministry of Education, is one of the earliest institutions committed to educational publishing after the establishment of P. R. China in 1949. After striving for six decades, HEP has developed into a major comprehensive publisher, with products in various forms and at different levels. Both for import and export, HEP has been striving to fill in the gap of domestic and foreign markets and meet the demand of global customers by collaborating with more than 200 partners throughout the world and selling products and services in 32 languages globally. Now, HEP ranks among China's top publishers in terms of copyright export volume and the world's top 50 largest publishing enterprises in terms of comprehensive strength.

The Frontiers Journals series published by HEP includes 28 English academic journals, covering the largest academic fields in China at present. Among the series, 13 have been indexed by SCI, 6 by EI, 2 by MEDLINE, 1 by A&HCI. HEP's academic monographs have won about 300 different kinds of publishing funds and awards both at home and abroad.

About Frontiers of Optoelectronics

Frontiers of Optoelectronics (FOE) aims at introducing the most recent research results and the cutting edge improvements in the area of photonics and optoelectronics. It is dedicated to be an important information platform for rapid communication and exchange between researchers in the related areas. The journal publishes review articles, research articles, letters, comments, special issues, and so on. The Editors-in-Chief are Academician Qihuang Gong from Peking University and Prof. Xinliang Zhang from Huazhong University of Science and Technology. FOE has been indexed by ESCI, Ei, SCOPUS, CSCD, Source Journals for Chinese Scientific and Technical Papers and Citations, etc. FOE is fully open access since 2022.