Figure 5
Results of density functional theory simulations. (a) Density of states (DOS) of a pristine Si84(OH)64 approximant (grey dotted curves, dNC = 1.5 nm) together with the DOS of a Si84(OH)64 approximant containing interstitial P (black solid curves). The latter is shown in (b) with an interstitial P-atom in the NC centre (Si-atoms: grey, O-atoms: red, H-atoms: white, P-atom: orange). For bulk Si (grey solid lines) the HOS-level of interstitial P is well below the VB-edge and hence no recombination centre. QC-induced widening of the fundamental gap results in the HOS energy of Si NCs approaching the P-induced defect level. As a consequence, small NCs (blue dotted line) are more strongly subject to PL quenching than larger NCs (red dashed line).
