The dye-sensitized solar cell (DSSC) has been studied by observing charge transfer from an organic terthiophene dye into a semiconductor nanoparticle. Using NMR and UV-Vis, we find characteristics of dye aggregation and a concomitant reduction in the electron transfer efficiency as measured by ultrafast transient absorption (TA) spectroscopy. Specifically, the NMR and UV-Vis spectra of the dye molecules indicate aggregates are readily formed at high surface loading, or roughly a 20:1 dye:nanoparticle ratio. Upon analysis by TA spectroscopy the same samples show a dominant S1 state quenching process separate from the expected intersystem crossing and electron transfer (ET) S1 quenching pathways. We propose that the dominant process is concentration-quenching because it only appears at high surface coverage where aggregates are detected spectroscopically; at lower surface coverage (ratios of dye:nanoparticle of roughly 1:1) the ET mechanism is the dominant pathway for S1 reduction and the parasitic concentration-quenching pathway is not observed. We therefore suggest that planar oligothiophene dyes should be modified to frustrate packing on the surface in an effort to avoid concentration quenching losses, or that dye loading be considered when creating a DSSC from planar dye molecules. Classical molecular dynamics (MD) simulations are also presented to corroborate the experimental picture described above.

Experimental and computational study of concentration quenching in dye sensitized solar cells (DSSC)

245th National Meeting (2013)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.