Photoinduced Long-Distance Charge Transfer in Silicanes: The Stacking Matters

The generation of interlayer charge
transfer excitons
upon photoexcitation
is strongly desirable for two-dimensional (2D) materials stacked through
van der Waals interactions. In this work, we investigate photoinduced
charge transfer in silicanes (SiH) with three typical stackings. A
concept of the regional natural hole orbital and its conjugated particle
orbital is developed to characterize excited states in solids. This
method delivers bonding information about excited states and explains
the formation of certain types of states in nanomaterials. Utilizing
this tool, we demonstrate that SiH in the 1H and 6R stackings exhibits
an interlayer charge transfer distance that reaches ∼10 Å
under violet and near-ultraviolet radiation. The charge transfer is
attributed to the interlayer overlap between orbitals at the conduction
band minimum, which is disfavored by the 3R stacking. Our findings
suggest a new and feasible approach for tuning the optoelectronic
properties of Group 14 2D materials by altering their stackings.