While photovoltaic cell, or solar cell technology has progressed rapidly in recent years, it still suffers from the problem of being unable to completely capture all of the potential energy generated by the sun. Some energy is wasted with solar cells because it is converted into heat energy before it can be harnessed as electricity; heat energy cannot generally be changed into a productive form.

Current solar cells are only about 31 percent efficient, meaning that only about a third of the electrons captured by the cells can be used as electricity. The remainder are given off as heat, and these electrons begin to move more slowly as they cool down, meaning they no longer have enough energy to be converted into electricity. The U.S. Department of Energy has recently begun attempting to develop improved solar cells, with the goal of creating what has been termed the “ultimate solar cell”: one which converts all of the electrons excited by sunlight into usable electrical energy.

To accomplish this goal, the Department of Energy has identified a couple of changes that must be made to maximize energy captured.

First, the cooling rate of electrons in solar cells must be slowed down, so that they can be utilized before losing all of their energy. These electrons must then be able to be captured more quickly than they are in current solar cells. Finally, electrons must be removed as electricity from the cells with improved conducting wires that will minimize energy lost to dissipation.

Preliminary research has shown that lead selenide nanocrystals, also called “quantum dots,” are the most efficient substance so far in shifting electrons from solar cells to conductors, where they are converted into electrical power. Conductors made of titanium dioxide also help to prevent electrons from cooling down too rapidly.

As the Department of Energy continues to experiment with different types of materials for solar cells, further breakthroughs are sure to come.