Microcrystalline silicon-germanium solar cells with spectral sensitivities extending into 1300Â nm

High germanium (Ge) content hydrogenated microcrystalline silicon-germanium alloy (μc-Si1−xGex:H) has been prepared by conventional plasma enhanced chemical vapor deposition. The influence of the bombardment of energetic ions on the structural and electrical properties of high Ge content μc-Si1−xGex:H films was studied by Raman, transmission electron microscopy and conductivity measurements. Under low pressure and high levels of ion bombardment conditions, a mitigation of the rapid increase of Ge incorporation and a significant improvement of the homogeneous distribution of the crystal grains for high Ge content μc-Si1−xGex:H films were achieved. Consequently, an enhancement in the quantum efficiencies over 800 nm wavelengths and a spectral response extending to 1300 nm for μc-Si1−xGex:H solar cells were achieved by using an intrinsic layer with x=0.77.