Strong Coupling in Microcavities for Enhancing Photostability of High-Performance Organic Semiconductors

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In this project funded by the Chemical Structure, Dynamics, and Mechanisms A (CSDM-A) program of the Chemistry Division, Professor Oksana Ostroverkhova of Oregon State University is exploring a new route for improving the stability of carbon-based electronics (organic semiconductors) when they are exposed to light. Organic semiconductors are of interest due to their low cost and tunable properties. A broad range of applications, from photovoltaics to three-dimensional displays, have been demonstrated. Wide commercialization of organic electronics has been hindered by their relatively low stability when exposed to common environmental factors such as light and air. In this project, very thin films of organic semiconductor materials are placed in tiny microcavities, where they interact with light, creating hybrid light-matter states known as polaritons. Professor Ostroverkhova and her students are studying the effects of these polaritons on the speed and outcome of chemical reactions that cause the organic semiconductors to deteriorate. They are using light-absorption and theoretical modeling to study how properties of polaritons could be used to slow down degradation of the organic semiconductor molecules and to promoting self-healing if degradation does occur. The project integrates fundamental chemistry and physics with materials design and device technologies and provides educational resources and infrastructure for students involved in the project. Graduate and undergraduate students gain experience in the emergent field of polariton chemistry, and in advanced spectroscopy and numerical modeling techniques.The PI carries out a systematic investigation of how the properties of hybrid light-matter states and of the “dark” states (due to molecules not coupled to the cavity) control the rates of chemical reactions responsible for photodegradation and recovery of organic semiconductors. High-performance organic semiconductor model systems are used to quantify strong exciton-photon coupling-controlled enhancement of photostability depending on the photodegradation pathway in non-interacting (“isolated”) molecules and in molecular aggregates and to establish the feasibility for cavity-coupled vibrational states to promote reversal of the photodegradation. The broader impact of this project is in its potential impact on resolving the stability bottleneck of organic electronic devices and on the development of polaritonic devices, as well as student training, as mentioned above.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.