Abstract

In this presentation we discuss nanostructures including metal oxide nanowires and semiconductor quantum dots for solar cell applications. Optimized conditions for a reproducible synthesis of Zn2SnO4 nanowires are achieved, and the effect of dye adsorption on cell performance is investigated. A more than 0.1 V improvement on open-circuit voltage has been constantly observed when Zn2SnO4 nanowires are used as the photoanode instead of Zn2SnO4 nanoparticles. The higher open-circuit voltage of Zn2SnO4 nanowire-dye SSCs could be attributed to a suppressed back electron transfer process in the devices. We also present a physical method for the synthesis and assembly of semiconductor quantum dots on ternary oxide nanowire photoanodes. Due to the multiple exciton generation effect, QD sensitized solar cells have the potential to circumvent the Shockley-Queisser limit for solar cell efficiency. However, typical solution-based synthesis of colloidal QDs involve toxic wet chemicals and nontrivial ligand exchange processing, and the effects of the ligands on carrier transport have not been fully understood. Here we report a physical deposition-based, one-step QD synthesis and assembly on ternary metal oxide nanowires for photovoltaic applications. Using pulsed laser deposition (PLD), CdSe QDs are successfully coated on Zn2SnO4 nanowires without ligand molecules, and the coverage can be controlled by adjusting the laser fluence. Growth of QDs in dense nanowire network structures has also been achieved, and photovoltaic cells fabricated using this method exhibited promising device performance. This approach can be further applied for the assembly of QDs where ligand exchange is difficult, and could possibly lead to reduced fabrication cost and improved device performance