The effect of Mo back contact ageing on Cu(In,Ga)Se2 thin-film solar cells

In this work, we investigate the effect of ageing Mo-coated substrates in a dry and N-2 flooded cabinet. The influence was studied by preparing Cu(In,Ga)Se-2 solar cells and by comparing the electrical performance with devices where the Mo layer was not aged. The measurements used for this study were current-voltage (J-V), external quantum efficiency (EQE), secondary ion mass spectroscopy (SIMS) and capacitance-voltage (C-V). It was concluded that devices prepared with the aged Mo layer have, in average, an increase of 0.8% in efficiency compared with devices that had a fresh Mo layer. Devices with aged Mo exhibited a nominal increase of 12.5mV of open circuit voltage, a decrease of 1.1mA/cm(-2) of short circuit current and a fill factor increase of 2.4%. Heat treatment of fresh Mo layers in oxygen atmosphere was also studied as an alternative to ageing and was shown to provide a similar effect to the aged device's performance. Copyright (c) 2013 John Wiley & Sons, Ltd.