For solar panels, wringing every drop of energy from as many photons as possible is imperative. This goal has sent chemistry, materials science and electronic engineering researchers on a quest to boost the energy-absorption efficiency of photovoltaic devices, but existing techniques are now running up against limits set by the laws of physics.
Now, researchers from the University of Pennsylvania and Drexel University have experimentally demonstrated a new paradigm for solar cell construction which may ultimately make them less expensive, easier to manufacture and more efficient at harvesting energy from the sun.
The study was led by professor Andrew M. Rappe and research specialist Ilya Grinberg of the Department of Chemistry in Penn's School of Arts and Sciences, along with chair Peter K. Davies of the Department of Materials Science and Engineering in the School of Engineering and Applied Science, and professor Jonathan E. Spanier, of Drexel's Department of Materials Science and Engineering.
It was published in the journal Nature.
Existing solar cells all work in the same fundamental way: they absorb light, which excites electrons and causes them to flow in a certain direction. This flow of electrons is electric current. But to establish a consistent direction of their movement, or polarity, solar cells need to be made of two materials. Once an excited electron crosses over the interface from the material that absorbs the light to the material that will conduct the current, it can't cross back, giving it a direction.
"There's a small category of materials, however, that when you shine light on them, the electron takes off in one particular direction without having to cross from one material to another," Rappe said. "We call this the 'bulk' photovoltaic effect, rather than the 'interface' effect that happens in existing solar cells. This phenomenon has been known since the 1970s, but we don't make solar c
|Contact: Evan Lerner|
University of Pennsylvania