Current-voltage analysis of band tail effects in CZTSSe through numerical simulation

Band tails in CZTSSe have been commonly attributed as the cause of the low open circuit voltages observed in many CZTSSe solar cells. Various simplified models have been proposed in literature to account for these band tail effects. However, in order to create a physically accurate numerical model for CZTSSe, it is necessary to build a more sophisticated band tail model such as those commonly used in simulation for other highly disordered materials such as a-Si. In this paper, a detailed numerical device model will be used to fit experimental data taken from multiple measurement techniques (i.e., multi-probe) to characterize the band tail distribution. The results of this model will be compared to analytical solutions derived for the band tail distribution for CZTSSe. Developing such a complete model is an important step in addressing the causes of low open circuit voltages, which limit the performance of these devices.