National Renewable Energy Laboratory (NREL), United States

II-IV-V2 materials: Inexpensive III-V analogs for high-efficiency photovoltaics

III-V materials have been used as the building blocks of the highest efficiency single and multijunction photovoltaics to date. However, large-scale adoption of these materials for solar energy harvesting has been hampered by the high cost of the group III elements, Ga and In, and the need for high-cost substrates such as Ge and GaAs. The II-IV-V2 materials provide an alternative pathway: these materials are analogous to III-Vs, but group III elements are replaced by alternating group II and group IV elements, similar to the relationship between CdTe and CIGS. In this case, inexpensive elements such as Zn, Sn, and Si can be used, but the materials offer a similar phase space to the III-Vs, with opportunities for alloying and lattice-matched multilayer stacks. This talk will focus on two materials: ZnSiP2, a wide band gap material that is lattice-matched to Si for tandem PV applications using a Si bottom cell, and ZnSnN2, a narrow-gap, wurtzite-structured material similar to InGaN, for thin film applications.


Adele Tamboli's research focuses on photovoltaic materials and devices, including silicon-based tandem solar cells and novel epitaxial and thin-film absorber materials. As part of the High Efficiency Crystalline PV research group, Dr. Tamboli is involved in a variety of projects to advance PV efficiency while maintaining or improving upon the existing cost structure and proven reliability of silicon PV. Her current projects include direct growth of III-V materials on silicon, III-V/Si mechanically stacked tandems, and II-IV-V2 materials (e.g., ZnSiP2 and ZnSnN2). Before joining NREL, Dr. Tamboli worked on Si and Si/III-V microwire array materials for photovoltaics and solar fuels as a postdoc at Caltech, as well as III-nitride microcavity lasers and light-emitting diodes as a Ph.D. student at the University of California, Santa Barbara.