Electroluminescence system for analysis of defects in CdTe cells and modules

A highly versatile electroluminescence (EL) system was constructed to measure various non-uniformities in CdTe photovoltaic devices spanning a wide range of areas. The emitted photons from these devices are detected with a Si-CCD camera. A small-area cell with a thick and thin CdS region was investigated, and a separate set of cells with varying CdCl₂ treatment. Several modules were also investigated, demonstrating different defects. Such defects include a shunt, likely due to a defect that existed before the cell layers were deposited, and a conductive bridge across scribe line in a CdTe module. The mean EL signal has been found to vary exponentially with the open-circuit voltage (V_OC) of CdTe devices and holds for devices with differing CdS thicknesses and CdCl₂ treatment. A GaAs device was also compared to this trend.