Identifying parasitic current pathways in CIGS solar cells by modelling dark JV response

The presence of undetermined shunt pathways in CIGS solar cells can be severely limiting to the reproducibility of individual cell efficiency, both at lab-scale, and particularly in a roll-to-roll process. Here, a general model that describes the dark J-V characteristics of CIGS devices, accounting for three separate shunting pathways (Ohmic and non-Ohmic components, and a tunneling component), is presented. Excellent agreement between the model and experimental data is demonstrated throughout the temperature range 183 - 323K, whereas simpler models fail to accurate fit the data. To demonstrate the effectiveness of the model, a case study was carried out to investigate the cause of the large spread in efficiency in a single batch of CIGS cells. The model showed that the low efficiencies were entirely due to a higher prevalence of the three different shunt pathways, but not due to any degradation of the main junction. This methodology may therefore be used for rapid diagnosis of low (or inconsistent) efficiencies.