The aim of this work is to optimize a-SixC1-x:H alloy material characteristics in order to improve the performance of large area single and stacked p-i-n sensors. The efforts are focused mainly on n- and p-type doped layers at low doping levels with and without carbon. The hydrogen content and optoelectronic properties of the single layers were determined through infrared and visible spectroscopy, temperature-dependent conductivity, and were complemented by CPM measurements. Junction properties, carrier transport, photogeneration and collection efficiency are investigated using dark and illuminated current-voltage characteristics and spectral response measurements, with and without additional background illumination and under different light bias conditions.