New international research at the Department of Energy's Lawrence Berkeley National Laboratory was able to create highly efficient silicon solar cells in only seven steps. By simplifying the steps to make solar cells it can help reduce the costs of making solar panels, thereby reducing the cost of solar power overall.
"The solar cell industry is driven by the need to reduce costs and increase performance," said Berkeley Lab visiting researcher James Bullock. Bullock, from Australian National University (ANU) was the lead author, which was published in Nature Energy. Bullock was joined by researchers from the Berkeley lab, the Swiss Federal Institute of Technology of Lausanne (EPFL) and other ANU scientists.
The new research produced a dopant free asymmetric heterocontact (DASH) silicon solar cell with an average efficiency above 19 percent. That’s as or more efficient than most commercially available solar panels. SunPower’s Maxeon solar cells are 24 percent efficient and among the most efficient silicon solar panels available, for instance.
The solar cell is dopant-free and uses a simple coating process for layers on the top and bottom of the device, the lab said. The doping process adds complexity to the solar cell manufacturing process.
"Conventional silicon solar cells use a process called impurity doping, which does bring about a number of limitations that are making further progress increasingly difficult,” Bullock explained.
“Most of today's solar cells use crystalline silicon wafers. The wafer itself, and sometimes the layers deposited on the wafer, are doped with atoms that either have electrons to spare when they bond with silicon atoms, or alternatively generate electron deficiencies, or "holes." In both cases, this doping enhances electrical conductivity.”
Such cells can exceed 20 percent efficiency at converting sunlight into electricity. The new cells use a crystalline silicon wafer but use applied layers of amorphous silicon with ultrathin coatings of molybdenum oxide on its top and lithium fluoride on its bottom. The layers are only nanometers thick and provide dopant-free contacts for holes and electrons. Both materials are transparent, and they have complementary electronic structures that are well-suited for solar cells. In the past non-dopant silicon cells had only reach efficiencies of 14 percent.
"Moly oxide and lithium fluoride have properties that make them ideal for dopant-free electrical contacts," explained research lead Ali Javey, a program leader of Electronic Materials at Berkeley Lab and a professor of Electrical Engineering and Computer Sciences at UC Berkeley.
Beyond solar cells the materials could also prove useful in semiconductors, which would make the technology even more useful and widespread.Tweet