| Quantum dot sensitized solar cells (QDSSCs) are recognized as a promising new technology for making cost efficient photovoltaic devices. In this project, QDSSCs are based on CdSe quantum dots (QDs) attached to ternary zinc tin oxide (ZTO) nanowires. Ternary oxides are of interest because they afford a wide latitude for compositional tuning of semiconductor properties. In any device that is to be subjected to the conditions of field deployment, the long term stability of all components of the device must be assured. Processes such as QD detachment or QD-nanowire dissolution and corrosion might significantly degrade solar cell performance over time. In this dissertation, stability aspects of QDSSCs are examined in detail, from the dissolution and alteration of ternary oxide materials to the attachment, detachment and dissolution of QDs on oxide surfaces. We find that ZTO is likely to survive long-term deployment, but that small amounts of surface alteration will take place. More importantly, solution-based QDs capped with organic stabilizing molecules demonstrate ligand-dependent attachment and detachment behaviors but are less prone to dissolution. Pulsed laser deposited QDs, however, are prone to longer-term dissolution. Post-deposition capping molecules could improve stability but might inhibit electron transfer. Long-term QDSSC stability is a balance between protection of key materials but avoiding inhibition of electron transfer needed for solar cell operation. |
