The exciton is a critical part of each of the processes leading to photocurrents in Organic PhotoVoltaics (OPVs), and being able to control the location, lifetime and energy of the exciton is essential to achieving high efficiency.   We have investigated methods for tuning exciton energies and controlling their migration paths, both intramolecularly and within a thin film.  I will discuss our most recent work with the efficient use of multiple absorbers to efficiently harvest photons through the entire visible spectrum.   In particular, we have used careful control of exciton and carrier energies to design and implement sensitizers that give fullerene films efficient light collection throughout most of the visible spectrum.  I will also discuss a new approach to designing materials for OPVs that involves symmetry breaking charge transfer.  These materials are symmetric molecules that spontaneously form an intramolecular charge transfer complex, with nearly complete one electron transfer from one part of the molecule to another.  This intramolecular CT state readily forms a charge separated state at the D/A interface of the OPV.  We have explored these materials as both donors and acceptors in OPVs and found that they give good performance and high Voc.

Sensitization and symmetry breaking charge transfer in organic solar cells

248th National Meeting (2014)

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