Towards the CdS/SnSe solar cell optimization: Understanding the transport mechanisms

In this work, numerical simulation results on SnSe solar cells are presented. The influence of loss mechanisms such as radiative recombination, SnSe bulk recombination, and CdS/SnSe interface recombination on the device is studied in detail under and without the influence of resistances for the first time. In the first step, our model is validated by accurately reproducing the experimental available data. We found that non-radiative recombination originated by SnSe bulk defects in combination with high series resistances are dominant loss mechanisms, resulting in efficiency values lower than 2 %. In addition, the important role of the CdS/SnSe interface is also evidenced, since SnSe solar cells without bulk defects and resistances would not be able to overcome the efficiency barrier of 10 % because of the cliff-like band alignment. The role of each loss mechanism on SnSe solar cell performance was studied as a function of material thicknesses, carrier concentrations, bulk and interface defects, and resistances for device optimization. We demonstrated that conversion efficiency of 21.8 % with an open-circuit voltage, short-circuit current density, and fill factor values of 0.82 V, 31.6 mA/cm², 84.6 %, respectively can be achieved in the optimized device under the standard conditions of AM 1.5G illumination and 300 K.