Symmetry-Breaking Charge Separation Materials for Single-junction Organic Photovoltaics

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Symmetry-breaking charge separation (SB-CS) is one of the key steps in the primary charge separation process of the photosynthesis reaction center, where structural or environmental fluctuations break the excited state symmetry of the chromophoric pair and yield a charge-separated (CS) state. Organic photovoltaics (OPVs) are of growing interest for indoor light harvesting, building, and vehicle-integrated photovoltaics applications. Unlike conventional inorganic photovoltaics, OPV devices conventionally use a combination oforganic donor and acceptor molecules to dissociate excitons and generate photocurrent. There have been rapid advances in the performance of OPVs in the past few years, and single-junction OPVs have achieved a power conversion efficiency above 19%. This process involves intermolecular interactions in the solid state, unlike the SB-CS materials, which involve intramolecular interaction. However, this raises a fascinating question, what if SB-CS materials could be engineered in the solid state to take advantage of both intramolecular and intermolecular effects? Could this allow long-lived charge generation in low-dielectric solid-state environments? This project will venture into this less-explored area of SB-CS material-based single-junction OPVs. SB-CS materials are reported to generate a short-lived CS state via intramolecular interaction. This proposal aims to enhance the CS lifetime of SB-CS material in the solid state by exploiting intermolecular interactions to innovate an efficient charge transfer model. The rigid orthogonal or near-orthogonal arrangement of chromophores is considered an elegant design that renders efficient charge separation. Molecular functionalization and structural and photophysical characterization of materials will be performed to address the scientific challenge. A single-compartment OPV device will be made, and the project's completion will unleash paths for further systematic improvement of single-junction OPVs.