Exploring the Nature of Charge Transfer States at Molecular and Hybrid Organic-Inorganic Heterojunctions

Project: Research project

Project Details


The field of organic photovoltaics (OPVs) has now reached a stage where further advances in the power conversion efficiency (current state-of-the-art = 17.4%) require a fundamental understanding of all possible sources of energy loss in the conversion process and the development of strategies to eliminate them systematically. Charge transfer (CT) states at the donor-acceptor (DA) interface of OPVs are a key intermediary in both the charge photogeneration and recombination processes and have been shown to underlie the thermodynamic limiting efficiency of OPV cells. The presence of CT states is the primary reason why OPV cells exhibit a larger open-circuit voltage loss than their inorganic counterparts and is why understanding their role in charge separation and non-radiative recombination energy losses is so crucial.Historically, these energy losses have been viewed in the context of a single CT state; however, recent work has shown that a substantial component of the loss stems from the distribution of CT states that results from the energetic, positional, orientational, and conformational disorder in typical DA heterojunctions. The proposed research seeks to separate this inhomogeneous component of CT energy loss from the homogeneous component related to the electronic properties of a given pair of donor and acceptor molecules. The objective is to understand the electronic, morphological, and environmental factors that influence the magnitude of the inhomogeneous component and identify whether there are fundamental trade-offs between it and other key processes such as efficient charge separation. This insight will subsequently be applied to understand the reduced energy loss that has recently been observed in non-fullerene organic solar cells and to explore a new paradigm for reducing loss in hybridized donor-acceptor systems with emergent, supramolecular orbitals. If successful, this work will provide a scientific basis for reducing voltage loss in future organic solar cells and strengthen the technological leadership of the U.S. in the development of materials for solar energy conversion.
Effective start/end date8/15/208/14/23


  • Basic Energy Sciences


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