Silicon nanocrystals as a photoluminescence down shifter for solar cells

The effects of a Si-rich silicon oxide (SRO) layer containing silicon nanocrystals as photoluminescence down-shifter layer on a conventional Si solar cell were investigated. Two SRO layers with different thicknesses but same composition were deposited on top of Si solar cells by plasma-enhanced chemical vapor deposition and followed by high temperature annealing to precipitate silicon nanocrystals. The SRO layers absorb efficiently high energy photons (especially higher than twice Si bandgap) and emit photons at longer wavelength, which are in turn absorbed by Si. A relative increase of about 14% to the internal quantum efficiency has been observed.