Improving the Efficiency of Dye-Sensitized Solar Cells

Alex Huhn with Prof. Robert Hamers, Rose Ruther, Kacie Louis, Joe Yeager, & Ryan Franking

UW Department of Chemistry

Commercially produced solar cells are typically single-crystalline silicon solar cells because they are the most efficient kind presently available. Dye-sensitized solar cells are an alternative variety; however, they are not a currently viable form of alternative energy due to their inefficiency. Zinc oxide nanorods (rod-like formations of zinc oxide only a few hundred nanometers tall) form a crucial component of a zinc oxide dye-sensitized solar cell. Efficiency is dependent on the amount of sunlight that can be absorbed by the solar cell; the greater the surface area of zinc oxide nanorods, the greater the sunlight absorption. The most evident means of increasing the surface area of the zinc oxide nanorods is by increasing the length of each nanorod.

We initially grew zinc oxide nanorods on silicon samples placed in a growth solution in a drying oven. To increase the length of the nanorods, we hypothesized that a continuous bathing of the growth solution over the silicon samples would generate longer nanorods than a stagnant solution. We constructed a flow cell, an apparatus designed to filter new growth solution through a jacketed chromatography column while removing old growth solution from the chamber containing the silicon samples. The scanning electron microscopy of the zinc oxide nanorods created from the flow cell were up to ten times longer and almost twice as wide as the nanorods not grown using the flow cell. The flow cell process created 27.5 times more area of nanorods per square centimeter. Although the flow cell treatment increased the efficiency of zinc oxide nanorods, solar cells made with the flow cell treated nanorods still had an efficiency of less than 1%.