Impedance spectroscopy applied to the characterisation of a-Si:H solar cells during light degradation

We have applied an impedance spectroscopy technique to study the performance and degradation mechanisms of a-Si:H solar cells to gain greater understanding of their fundamental properties and to achieve the production of devices with improved performance. Our results showed that over a limited range of frequencies and bias voltages the cell can be modelled as an equivalent circuit composed of a capacitor and resistor in parallel. Otherwise, one or more parameters of the equivalent circuit are functions of frequency. Preliminary results show that this technique is very sensitive to the changes that take place during the optical degradation processes. This technique provides complementary information about the production, transport and decay/recombination of the charge carriers