In-Situ Studies of Photoluminescence Quenching in Single Crystal Quantum Dot Sensitized Solar Cells

Single crystal quantum dot sensitized solar cells (QDSSC) are a promising photovoltaic system in which collection of multiple charge carriers per photon has recently been reported.\footnote{Justin B. Sambur, Thomas Novet, B.A. Parkinson, \textit{Science} \textbf{330} (6000) 63-66} Utilizing time-correlated single photon counting we have studied both the fluorescence intensity and fluorescence decay time from CdSe quantum dots coupled to both single crystal TiO$_{2}$ and ZnO substrates through short and long chain ligands. We find that for all configurations the fluorescence decay time is quenched compared to unbound quantum dots in solution, while the photovoltaic properties of the system strongly depend on the chain-length of the ligand. These results suggest there exist interactions between either the individual quantum dots or the quantum dots and substrate that may compete with the charge injection process in QDSSCs.