Figure 9: Energy-level diagrams for undoped, B-doped, P-doped, and lightly codoped Si NCs. Three configurations for the light codoping of B and P have been investigated: BP-1 (P nearest neighbors B), BP-2 (P is 90° apart from B), and BP-3 (P and B are in crossing-diameter locations). Filled (empty) circles indicate that the energy levels are occupied (unoccupied) by electrons. (Reprinted from [38] copyright 2012 Springer.)