In-process diagnostics of recombination centres in structures of large-area solar cells

The paper refers to a possibility to check carrier lifetime in the area close to the PN junction measuring forward characteristics at low current, densities, where generation-recombination portion of the current density dominates. The measurement allows one to determine energy level of dominant recombination centres and evaluate their concentration. The carrier lifetime in volume of the cell body can be evaluated using local irradiation of the surface of large-area solar cells with a laser diode (λ=870 nm) from measured values of open circuit voltage V_oc. The method can give information about recombination centres distribution in large-area solar cells. From V_oc distribution, position and extent of local defects can also be determined. Solar cell diagnostic methods can be used to investigate the influence of technology on characteristics of solar cells, with the aim of increasing efficiency and reliability of solar cells.