Hitchhiking triplet states to better understand organic semiconductors: Insights into their structure–function relationship gained by time-resolved EPR spectroscopy

Organic semiconductors play increasingly important roles in our daily lives. Insights into their structure–function relationship is crucial for the rational design of these materials. Here, we present three examples of how time-resolved EPR (TREPR) spectroscopy can contribute to our understanding of organic semiconductors investigating light-induced short-lived triplet states: (i) overall orientation and degree of ordering of polymer films on substrates, (ii) the direct optical excitation of triplet states from the singlet ground state, completing our picture of potential triplet pathways, and (iii) identifying the building block resembling the electronic structure of the corresponding polymer. Taken together, TREPR spectroscopy of triplet states provides highly relevant insight complementary to other methods, adding to our understanding of the structure–function relationship of organic semiconductors.