High rate deposition and in situ doping of silicon films for solar cells on glass

For solar cells on low cost float glass substrates a thickness of 20 μm of a poly-Si film is sufficient to absorb light. Between the substrate and active layer a combination of metal nitride and graphite enables the recrystallization of the nanocrystalline deposited silicon. Efficient deposition rates for the in situ p-doped Si absorber up to 300 nm/min are achieved by means of a PECVD process in combination with trichlorosilane (SiHCl3), boron trichloride (BCl3) and hydrogen (H2). The substrate temperature is chosen between 770 and 820 K. The active Si films are recrystallized by a line-shaped electron beam which crosses the substrate at velocity up to 10 cm/s.