Because of the quantum confinement effect, silicon nanocrystals exhibit some new features different from bulk silicon, such as enhanced photoluminescence and adjustable optical band gap, etc. Silicon nanocrystals have attracted much attention in the fields of microelectronics, photovoltaic, biomedicine and so on. In this paper, the different preparation methods of freestanding silicon nanocrystals and silicon nanocrystals embedded in thin films are reviewed, the advantages and disadvantages of different preparation methods are analyzed. Furthermore, the applications of silicon nanocrystals are focused on photovoltaic, including solar cells made up of pure silicon-nanocrystal films, organic solar cells combined with silicon nanocrystals, and silicon nanocrystals ink for solar cells.

Contents
1 Introduction
2 Synthesis of Si nanocrystals
2.1 Synthesis of freestanding Si nanocrystals
2.2 Synthesis of Si nanocrystals embedded in films
3 Applications of Si nanocrystals in solar cells
3.1 Si nanocrystal films as the emitter or optical absorb layer in solar cells
3.2 Organic solar cells combined with silicon nanocrystals
3.3 Silicon nanocrystals ink for solar cells
4 Conclusion