Stable a-Si: H-Based Multijunction Solar Cells with Guidance from Real-Time Optics

Phase diagrams that characterize plasma-enhanced chemical vapor deposition of Si thin films at low substrate temperature (200 C) have been established using real time spectroscopic ellipsometry as a probe of thin film microstructural evolution and optical properties. These deposition phase diagrams describe the regimes over which predominantly amorphous and microcrystalline Si phases are obtained as a function of the accumulated film thickness and the hydrogen-to-silane gas flow ratio R=[H2]/[SiH4].