Recently, increasing the efficiency of dye-sensitized solar cells (DSSCs) beyond the Shockley–Queisser limit has been an area of focus in the solar cell community. Molecular photon upconversion, by way of triplet-triplet annihilation (TTA-UC), is one strategy to increase solar cell efficiencies by utilizing sub-bandgap light to generate photocurrent. With self-assembled bilayers of sensitizer and acceptor molecules on nanocrystalline metal oxide films, we have demonstrated direct photocurrent generation from TTA-UC in dye-sensitized solar cells. The rates of the energy and electron transfer processes in our upconversion DSSC have been determined through a combination of steady-state and time-resolved emission  along with transient absorption spectroscopy. Because triplet energy transfer through the acceptor film and subsequent annihilation is an isoenergetic process, it is difficult to directly probe with room temperature transient absorption spectroscopy. In this work we probe the rate of this energy migration process and the solvent effect on the reorganization energy using temperature controlled measurements.  This information could help guide the design of more efficient self-assembled UC films and is a critical step towards the long-term goal of generating a practical UC solar cell.

Triplet energy transfer dynamics at the bilayer-solvent interface for application in molecular upconversion DSSCs

256th National Meeting (2018)

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