Quantum efficiency measurements of down-shifting using silicon nanocrystals for photovoltaic applications

Silicon nanocrystal (Si-NC) luminescent down-shifting materials for photovoltaic (PV) applications were fabricated by ion implantation and plasma-enhanced chemical vapor deposition (PECVD). The absolute optical conversion efficiency of the Si-NC-emitted photoluminescence was measured using conventional methods, and an optical set-up involving an integrating sphere. Modeling shows that down-shifting the light incident on a single-junction silicon cell (SJSC) can improve the cell performance if the optical conversion efficiency is sufficiently high. The measured conversion efficiency of the Si-NCs in a fused silica host was found to range from 0.8% to 1.84% and was compared with the efficiency required to maintain the performance of a SJSC.