Understanding and Improving Triplet Exciton Transfer in Sensitized Silicon Solar Cells

The triplet exciton transfer from tetracene to silicon has recently found interest in the context of efficiently harvesting high-energy photons with sensitized silicon solar cells. Density-functional calculations presented here show that at covalently bonded, atomically perfect interfaces, no exciton transfer can be expected. The situation changes, however, as soon as realistic interface models are taken into account. Unsaturated Si dangling bonds on n-type silicon assist the exciton transfer. The calculations show furthermore that incompletely bonded interfaces as well as horizontally attached seed molecules foster excitation transfer. Backfilling the interface, on the other hand, is detrimental to the interface's transport properties.