Single and multijunction solar cells with 1.0 eV Si-Ge-Sn junction

Recent development of Si-Ge-Sn ternary alloys offers an alternative to 1.0 eV bandgap materials for multijunction solar cells. Main advantages of these alloys are tunable gap energy and variable lattice parameter, which can be fitted into the existing designs, thus resulting in a lattice matched solution. Recent growth, optical and structural results from Si-Ge-Sn with ~ 1 eV gaps and lattice matched to Ge substrates are presented. Based on simple device models, prototype single and triple junction cells with SiGeSn junction have been fabricated. Device measurements show that the performance of Si-Ge-Sn material is comparable to other 1.0 eV semiconductors.