Carrier multiplication is not what happens when you cross FedEx with UPS. That’s Fed-Up. And it’s not the scientific name for pigeon breeding. It is, however, the latest buzz term soaring through the thin-film solar industry. Solar cell efficiency has long been limited due to the fact that a photon striking a solar cell can “excite” only one electron-hole connection, regardless of the amount of energy within the photon. Any excess photon energy is lost as heat.
Carrier multiplication (CM) occurs when a cell material allows for one photon to excite more than one electron into the electric current flowing from the solar cell. Researchers from Ben-Gurion University (BGU) in southern Israel have discovered just such a cell - which could mean much greater conversion efficiency for thin-film cells.
CM has also been found in nano-crystalline solar cells (quantum dots) and is considered to be a major advantage for those cells. Yet the BGU researchers have shown that CM occurs much more successfully in lead sulfide (PbS) or lead selenide (PbSe) solar cells. These cells are less complex than nano-crystalline cells and were prepared inexpensively.
It’s easy to see how carrier multiplication could have a huge effect on thin-film solar panels. It effectively doubles the efficiency of the solar cell. BGU and its research team have been getting a lot of attention in recent weeks from a solar sector eager and waiting for just such a development. CM could be the ticket to a high-efficiency, low-cost, aesthetically pleasing solar cell.
One potential issue that could arise, however, is the prospect of mass producing lead-based solar cells. Lead is a heavy metal and a neurotoxin. Could safety and environmental concerns dampen development?