Enhanced Photostability through Rapid Exciton Decay in Desymmetrized Cyclopentannulated Acenes with Strong Face-to-Face pi Stacking

Published

January 28, 2026

Author(s)

Chad Cruz, Karl Thorley, Zachary Knepp, Jared Wahlstrand, Gil Repa, John Stephenson, Sean Parkin, Lisa Fredin, John Anthony, Emily Bittle

Abstract

The photophysics of organic semiconductors impacts their efficiency in optoelectronic devices where exciton transitions, including singlet fission, intersystem crossing and the formation of charge transfer states influence the ability to convert between bright and dark states and to dissociate into free charges. Unfortunately, photodegradation and spurious signals often confound the results of optical studies, especially of important triplet states. Here four asymmetric cyclopentannulated acenes are synthesized and studied. This system represents an extreme in photophysics achieved via molecular design to fully quench the photoluminescence and bypass triplet formation allowing for comparative studies with other highly absorbing acenes. Rapid molecular exciton decay that is unaffected by strong electronic coupling induced by the crystal packing is found. The quick return to the ground state inhibits the formation of triplets and leads to heating in the solid state. These aceacenes are photostable both in solution and as single crystals, likely because the short excited-state lifetime diminishes the chances for deleterious photoreactions. Time-dependent density functional theory calculations highlight vibrational relaxation through the five-membered ring as a key driver of rapid internal conversion.

Citation

Chemistry of Materials

Volume

38

Issue

3

Pub Type

Journals

Download Paper

https://doi.org/10.1021/acs.chemmater.5c02815

Local Download

Keywords

organic semiconductors, ultrafast photophysics, internal conversion, thermal artifacts, triplet generation

Citation

Cruz, C. , Thorley, K. , Knepp, Z. , Wahlstrand, J. , Repa, G. , Stephenson, J. , Parkin, S. , Fredin, L. , Anthony, J. and Bittle, E. (2026), Enhanced Photostability through Rapid Exciton Decay in Desymmetrized Cyclopentannulated Acenes with Strong Face-to-Face pi Stacking, Chemistry of Materials, [online], https://doi.org/10.1021/acs.chemmater.5c02815, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=960810 (Accessed April 28, 2026)

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