Optical properties of microcrystalline materials

We use optical, photocurrent and photothermal deflection spectroscopies to study defects in microcrystalline silicon (<i>μc</i>-Si) thin films and diamond layers. Enhanced light absorption in μc-Si films and solar cells is due to several contributions: light scattering, change in the optical transition probability for strained and surface atoms and residual amorphous fraction. Low defect density (optical absorption with a coefficient, <i>α</i>, smaller than 0.1 cm−1 at about 0.8 eV, as measured by the constant photocurrent method), amorphous volume fraction below 10% and a distinct surface texture is typical for a material yielding a good efficiency <i>μc-Si</i> solar cells. Main defects in heteroepitaxial chemical vapor deposition diamond films are discussed.