Bridge‐ and Double‐Bonded O and NH on Fully OH‐ and NH 2 ‐Terminated Silicon Nanocrystals: Ground and Excited State Properties

The authors model fully hydroxyl‐ (OH‐) and amino‐ (NH 2 ‐) terminated silicon nanocrystals (Si‐NCs) by time‐dependent density functional theory (TD‐DFT), and replace OH or NH 2 groups by respective double‐ (=) or bridge‐bonded (>) groups  >/ = O or >/ = NH. Investigating ground state (GS) gaps and interface charge transfers (ICTs) from Si‐NCs to anion groups, the authors show the impact of >/ = O and >/ = NH. Excited state (ES) calculations yielded transition energies E trans , oscillator strengths f osc and transition ratesA A b s. The exciton binding energy R * increases with ICT modulation in particular for >/ = O. Increase ofA A b sis high for =O and comparatively low for >O which correlates with increased (decreased) ionisation of =O (>O), as compared to nominal OH termination. Findings are also met by >/=NH on Si‐NCs, though the authors find the results there to be less apparent which is arguably originating from the specific anionic nature of N. As a result, Si‐NCs with >O and in particular =O bonds show significantly increased optical activity, but also higher R * values. The latter hampers exciton dissociation, hence carrier transport, and results in an increased redshift in photoluminescence (PL). These statements apply also to Si 3 N 4 ‐embedded Si‐NCs, though the differences there are less articulate.