A Device Model for Rb-Conditioned Chalcopyrite Solar Cells

We present a comprehensive device model for Cu(In,Ga)Se $_{2}$ (CIGSe) thin-film solar cells based on numerical SCAPS-1D simulations. The model reproduces the experimentally determined current-voltage and capacitance-voltage characteristics of a Rb-free reference device, a sample that underwent an RbF-treatment, and a sample based on a CIGSe/RbInSe $_{2}$ -stack. According to this model, and in agreement with experimental findings, the main consequences of both Rb-conditionings are an increased doping-density and a defect passivation in the CIGSe as well as the formation of a photocurrent barrier at the hetero interface. With the numerical model established, fundamental aspects of the Rb-conditioning, e.g., the differentiation between its effect on bulk and interface recombination are discussed. Additionally, temperature dependent current-voltage analysis is employed in order to test the model's predictions regarding the interaction of Rb with an injection-current barrier at the back contact of the device. Both the simulation and the temperature dependent current-voltage measurements lead to the result that the RbF-PDT is increasing the height of this barrier, while the deposition of RbInSe $_{2}$ is decreasing it.