In an advance that could push cheap, ubiquitous solar power closer to reality, University of Michigan researchers have found a way to coax electrons to travel much further than was previously thought possible in the materials often used for organic solar cells and other organic semiconductors.
Unlike the inorganic solar cells widely used today, organics can be made of inexpensive, flexible carbon-based materials like plastic. That’s a dramatic increase; in today’s organic cells, electrons can travel only a few hundred nanometers or less.
Materials like silicon, used in today’s inorganic solar cells and other semiconductors, have tightly bound atomic networks that make it easy for electrons to travel through the material.
The surface of today’s organic solar cells must be covered with a conductive electrode that collects electrons at the point where they’re initially generated.
“This discovery essentially gives us a new knob to turn as we design organic solar cells and other organic semiconductor devices,” said Quinn Burlingame, a U-M electrical engineering and computer science graduate researcher and author on the study.
Using a common technique called vacuum thermal evaporation, they layered in a thin film of C60 fullerenes-each made of 60 carbon atoms-on top of an organic cell’s power-producing layer, where the photons from sunlight knock electrons loose from their associated molecules.