Simulation of Heat Loss in CZTSSe Thin Film Solar Cells: A Coupled Optical-Electrical-Thermal Modeling

A coupled optical-electrical-thermal modeling has been developed to investigate the heat generation in CZTSSe solar cells via Thermalization, Joule heat, Peltier heat, Surface Recombination heat, and non-radiative recombination heat and also the heat dissipation via convective and radiative cooling. These were calculated and displayed in 2D and 3D maps either at zero bias or open-circuit voltage (V oc) conditions. At V=0, the heat is generated mainly at the junction of CZTSSe/CdS where the thermalization and Joule heats are dominantly higher compared to non-radiative (SRH and Auger) recombination heat. However, at V=V oc , the nan-radiative recombination heat becomes comparatively higher than the Joule heating whereas the thermalization remains highest as before. Apart from the bulk heating factors, we also studied the surface recombination and Peltier heat generation. The surface recombination heat is higher at V=V oc compared to at V=0 while the Peltier heat is zero at V=V oc which can be explained by looking at the energy band diagrams at these voltages. The total heat generation does not change much across the cell thickness (<5×10 9 W/m 3) as the cell is quite thin. Nevertheless, the individual impact of every heat generation factor on power-density and current-voltage characteristics of the cell reveals that the thermalization, Joule, and non-radiative recombination heats reduce the open-circuit voltage of the cell from 0.54 V to 0.49 V (∆V = 0.047 V) while the Peltier and surface recombination heat is less effective. The temperature of the cell shows a small distribution across the cell (0.01 K). However, the temperature of the initial study at 293 K increases to 315-320 K for the coupled study. At this increased temperature, the short current-density doesn’t change but the fill factor decreases from 73.8% to 71.8% and, therefore, the energy conversion efficiency of the cell falls by 11.11% (from initial 12.78% to 11.36%). All the total heat dissipation, convective, and radiation cooling follow a similar trend to the total heat generation but convective cooling is the dominant component of dissipation.