New carrier-selective contact materials for silicon solar cells

Current record crystalline silicon conversion efficiency of 25.6% is still about 3.5% away from its thermodynamic limit. Losses are principally attributed to parasitic optical absorption and carrier recombination, both related to the properties of the contact materials interfacing directly crystalline silicon. Thus, one approach to lead silicon solar cells to an efficiency breakthrough tackles the implementation of novel wide-bandgap carrier-selective contacts (CSC).

These transparent films, or stack of films, shall have a large conductivity for the desired type of carrier—while blocking transport of the other type—and form an ideal interface with low density of interface trap states; they shall hence ensure the extraction at the quasi-Fermi energy of one carrier type at each cell terminal, while simultaneously provide nearly perfect passivation of the silicon surface.

The Defect Lab is involved in the characterization of III-V and metal oxide materials and their interface with silicon to assess their suitability as potential new CSC. This research is primarily funded by the U.S. Department of Energy SunShot program, through the Foundational Program to Advance Cell Efficiency II (FPACE II).