Covalent organic frameworks show great potential for efficient energy transport

An interdisciplinary research team from LMU, Technical University of Munich (TUM) and the University of Oxford has used a new spectroscopic technique to investigate the diffusion of excited states in covalent organic frameworks (COFs).

These modular materials can be tailored to desired properties through targeted selection of components, offering a wide range of applications. This research reveals how energy can be efficiently transported within these crystalline semiconductor materials. This is a decisive advance for future optoelectronic applications such as sustainable photovoltaic systems and organic light-emitting diodes (OLEDs).

At the heart of the research published in the Journal of the American Chemical Society is a thin film of COF made from a highly crystalline porous material. By using cutting-edge spatiotemporal techniques such as photoluminescence microscopy and terahertz spectroscopy, combined with theoretical simulations, the research team revealed significantly high diffusion coefficients and diffusion lengths of several hundred nanometers.

“Thus, these thin films significantly exceed the known energy transport capabilities of similar organic materials,” said co-first author, PhD candidate in LMU’s Department of Physical Chemistry and Functional Nanomaterials. Laura Spieth said.

“Energy transport works very well even across structural defects, such as grain boundaries,” says Dr. K., a former doctoral candidate in the Physical Chemistry and Nano-Optics Group and second co-lead author of the study. Dr. Alexander Biewald added.

New prospects for sustainable organic material development

Temperature analysis provided further insight into the underlying mechanism. “The results show that both coherent and incoherent transport processes are involved,” explains Professor Frank Ortmann, co-author of the study.

Coherence refers to the orderly occurrence of waves of motion that are unhindered over long distances, allowing for fast, low-loss energy transfer. In contrast, incoherent processes are characterized by chaotic and random motion, require thermal activation, and are often less efficient.

These insights significantly contribute to our understanding of energy transport in COFs and demonstrate how molecular structure and organization within the crystal influence these processes.

“Our research demonstrates how interdisciplinary and international collaboration of researchers with expertise in synthesis, experimental analysis, and theoretical modeling enabled by electronic conversion is critical to the success of such research. ”, says the study’s corresponding author. Achim Kharczuf and Professor Thomas Bain.

The results open new prospects for the development of sustainable organic materials in optoelectronics such as photocatalysis and photovoltaics.