Hydrogenated amorphous silicon-germanium thin films with a narrow band gap for silicon-based solar cells

摘要

Hydrogenated amorphous silicon-germanium (a-Si_xGe _(1-x):H) thin films were grown using very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD, 27.13 MHz). The films were used in a silicon-based thin film solar cell. The films were grown from a gas mixture of silane (SiH_4) and tunable germane (GeH_4) gas that was diluted in hydrogen (H_2). The results show that the optical band gap (E_g), optical adsorption coefficient (α), grain size and chemical composition depend on the germane contents of the films. The relationships among optical properties, structural properties, and chemical structural features were characterized by UV-visible spectroscopy (UV-vis), scanning electron microscopy (SEM), X-ray photoelectron spectrometer (XPS), and Raman spectroscopy. a-Si_xGe_(1-x):H solar cells with an efficiency of 5.59% were obtained the films.