Use of a gas jet deposition technique to prepare microcrystalline Si solar cells

A gas jet deposition technique has been used to prepare microcrystalline Si (μc-Si) i-layers for nip solar cells at rates of 15 Å/s. The red light absorbing capabilities make these cells an attractive alternative to a-SiGe in high efficiency multi-junction structures. The high deposition rates allow for fabrication of the required thick μc-Si i-layers in a similar amount of time to those used for high quality a-SiGe i-layers (rates of 1-3 Å/s). Using a 610 nm cutoff filter which only allows red light to strike the device, pre-light soaked short circuit currents of 8-10 mA/cm² and 2.7% red-light efficiencies have been obtained while AM1.5 white light efficiencies are above 7%. These efficiencies on average degrade only by 2% (stabilized efficiencies of 2.6%) after long-term light soaking (1000 hrs.). This small amount of degradation compares with the 15-17% degradation in efficiencies for a-SiGe cells subjected to similar irradiation treatments (final light-soaked red light efficiencies of 3.2%). Using the μc-Si nip structure as the bottom cell of an a-Si/μc-Si tandem-junction cell, pre-light soaking AM1.5 efficiencies of 9.8% have been achieved