Optical properties of microcrystalline materials

We use optical, photocurrent and photothermal deflection spectroscopies to study defects in microcrystalline silicon (mu c-Si) thin films and diamond layers. Enhanced light absorption in mu c-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, alpha, 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 mu c-Si solar cells. Main defects in heteroepitaxial chemical vapor deposition diamond films are discussed. (C) 1998 Elsevier Science B.V. All rights reserved.