Correlation between structural properties and performances of microcrystalline silicon solar cells

Several series of microcrystalline silicon p-i-n solar cells were grown on glass substrates. The intrinsic layer of the devices was deposited by Very High Frequency Plasma Enhanced Chemical Vapor Deposition (VHF PECVD) at a frequency of 100 MHz. Various hydrogen concentrations and different pressures in the range 500-950 mTorr were used while maintaining the other deposition parameters constant. The n- and p-doped layers were kept identical. Micro-Raman spectroscopy, using 514 and 633 nm excitation sources, was performed on the devices with focused excitation light arriving either directly on the top or on the bottom layer (glass-side) of the device. The electrical performance of the cells is discussed in view of the microstructure of the active layer. In particular, when the intrinsic layer is grown at low pressure, a higher short circuit current density and a larger ordered phase fraction are found in the devices.