Nanocystalline silicon solar cells

Nanocrystalline silicon material has made rapid progress in the last several years and at present it can be defined as real device quality as a photoactive layer for solar cells. A number of innovative ideas, such as the deposition at the crystalline to amorphous transition, at high pressure depletion condition, by taming of the ion energy, by grading of the material growth, at reduced unwanted dopant incorporation, have helped to reach an efficiency of 10% for single junction nanocrystalline silicon cells. In situ plasma and gas phase diagnosis have contributed to the fast optimisation of deposition process parameters. Deposition rate, open circuit voltage and light confinement are some of most critical issues that are currently pursued. Materials with a defect density as low as 10¹⁵ cm⁻³ have been made, however, they are still not good enough for n–p junctions; the device structure is still of drift type in a p–i–n or n–i–p configuration.