| Popis: |
Amorphous semiconductors such as amorphous silicon (a-Si) have received much attention as a material for high-efficiency photovoltaic solar cells. Value of the optical absorption coefficient is of a great interest since it determines the optical property of material and the efficiency of the solar cells. In the present rudy, for high-sensitivity measurement of the optical absorption coefficient, constant photocurrent method (CPM) was established. In the CPM, the inverse of the number of photons, necessary to keep the photocurrent constant is measured as a function of the photon energy. Therefore, complicated system containing a high-sensitivity photodetector is needed. The quartz glass as the beam splitter and InGaAs and Si compound type photodetector were adopted. After that, the p-type silicon was measured as a correcting sample. Obtained CPM spectrum was set up to the absolute scale (optical absorption coefficient [cm^] scale) by matching the results of the transmission measurement. It was proved that present CPM system could measure the very weak optical absorption coefficient at approximately 10^ cm^. |
