One of the greatest challenges humanity faces is finding a way to provide the world's population with clean energy. Since sunlight is our most abundant source of energy, solar cells, which absorb sunlight and create electricity, will become increasingly important over the next several decades. There have been great advances recently using silicon and thin films of semiconductors to make solar cells and solar electricity is just starting to become economically competitive. It is still important, however, to drop the costs further so that it will be possible to utilize even more solar energy. After providing an overview of the solar cell technologies that are currently commercially available, Professor McGehee will describe a relatively new approach that could make it possible to print solar cells in roll-to-roll coating machines similar to those used to make newspapers. Professor McGehee will show how solar cells can be made with organic semiconductors and explain how these cells work.