Elucidating Orbital Delocalization Effects on Boosting Electrochemiluminescence Efficiency of Carbon Nitrides

• Published in: Advanced optical materials 2022-09, Vol.10 (18), p.n/a
• Main Authors: Fang, Yanfeng, Hou, Yuhua, Yang, Hong, Chen, Ran, Li, Wang, Ma, Jin, Han, Dan, Cao, Xuwen, Liu, Songqin, Shen, Yanfei, Zhang, Yuanjian
• Format: Article
• Language: English
• Subjects: Aqueous solutions; Carbon; Carbon nitride; carbon nitrides; Chemical reactions; Electrochemiluminescence; Electronic structure; energy conversion efficiency; Light emission; Materials science; Molecular structure; Optics; orbital delocalization; photoelectrochemistry; Photon emission
• ISSN: 2195-1071; 2195-1071
• DOI: 10.1002/adom.202201017

Highly efficient inter‐conversion of different types of energy is the core of science and technology. Among them, electrochemiluminescence (ECL), an emission of light excited by electrochemical reactions, has drawn attention as a powerful tool across diverse fields in addressing global energy, environment, and health challenges. Nonetheless, the ECL efficiency (ΦECL) of most luminophores in aqueous solutions is low, significantly hampering their broad applications. Along this line, developing ECL luminophores with high ΦECL and understanding the associated intrinsic factors is highly envisioned. Herein, taking carbon nitride (CN) with rigid 2D backbones as an emerging model luminophore, it is reported that the orbital delocalization is a unified and quantifiable factor for its ΦECL. Behind the complicated transformation of molecular structures of cyano‐terminal groups and triazine/heptazine basal frameworks, the orbital delocalization of CN is found to be generally improved at an elevated condensation temperature. Such intrinsic evolution in electronic structure favored the electron injection in excitation and follow‐up photon emission in ECL for CN. As a result, the cathodic ΦECL of CN is remarkably improved to a new milestone of 24‐fold greater than the previous record. Orbital delocalization, associated with the evolution of the complicated molecule during the thermal condensation of carbon nitrides, is disclosed as a unified and quantifiable intrinsic factor for their electrochemiluminescence (ECL) efficiency. Moreover, a general approach for evaluating ECL kinetics is established, which excludes the inevitable dependency between ECL efficiency and the photoluminescence quantum yield of luminophores.