Direct Examination of the Deactivation of the Boron-Oxygen Center in Cz-Si Solar Cells Under Regeneration Conditions via Electroluminescence

We examine the regeneration kinetics of the boron-oxygen defect in boron-doped p-type Czochralski-grown silicon (Cz-Si) solar cells as a function of the excess carrier concentration Delta n at the regeneration conditions, i.e., at elevated temperature (140 degrees C). To perform the regeneration, we apply different forward-bias voltages (V-appl) to solar cells in darkness and measure directly the emitted electroluminescence (EL) signal at different time steps during the regeneration of the cell. Measuring the EL signal emitted by the solar cell during regeneration, we are able to directly determine Delta n during regeneration for each applied voltage. In addition to the EL signal, we measure the electric current flowing through the solar cell during the regeneration process. This current is proportional to the overall recombination rate in the cell and, hence, reflects the changing bulk recombination during the regeneration process. From the measured time-dependent cell current, we determine the deactivation rate constant R-de of the boron-oxygen defect. Our experimental results unambiguously show that R-de increases proportionally with Delta n during the regeneration process.