Hydrosilylation Of Silicon Nanocrystals And Their Application In Solar Cells

Silicon nanocrystals (Si NCs) exhibit fascinating electronic and optical properties. Si NCs are now intensively studied for photovoltaic application. They can be used to fabricate novel solar cell (multiple-exciton solar cells, intermediate-band solar cells, and hot-carrier solar cells), or incorporated in conventional solar cells. It has been realized that during the processing of Si NCs surface modification must be carried out to render the dispersibility of Si NCs in desired media and retard the oxidation of Si NCs.Freestanding Si NCs with different sizes are synthesized in a plasma system. Efficient photoluminescence (PL) from Si NCs in the visible and near-infrared spectral regions has been obtained.The surface of as-synthesized hydrogen-passivated Si NCs is modified via a hydrosilylation scheme with styrene. dodecene and octadecene. It is found that the peak position of the PL from hydrosilylated Si NCs is hardly affected by the modifier or the hydrosilylation time, but the modification time. However, the quantum yield (QY) of the PL from hydosilylated Si NCs decreases with the increase of hydrosilylation time for all the samples with different modifier. During the storage of hydrosilylated Si NCs in air the PL from hydrosilylated Si NCs blueshifts, while the PL QY for hydosilylated Si NCs initially increases and then decreases. The underlying mechanisms for all the optical behavior of hydrosilylated Si NCs are discussed.Hydosilylated Si NCs are dispersed in solvents to form Si ink. Si-NC films are obtained at the surface of Si solar cells by means of ink-jet printing. The reflectance and the external quantum efficiency (EQE) of Si solar cell have been measured. Enhancement of solar cell efficiency up to 2.02% is observed. Both the antireflection of Si-NC films and the downshifting of Si NCs contribute to the efficiency enhancement.