Simulation of heat loss in Cu2ZnSn4S Se4− thin film solar cells: A coupled optical-electrical-thermal modeling

A coupled optical-electrical-thermal modeling has been developed to investigate the heat generation and dissipation in Cu 2 ZnSn 4 S x Se 4− x thin film solar cells. Five heat generation factors: Thermalization, Joule heat, Peltier heat, Surface Recombination heat, and non-radiative recombination heat (Shockley-Read-Hall and Auger) as well as two heat dissipation factors convective and radiative cooling were calculated and displayed in 2 and 3 dimensional maps. Thermalization is the dominant heat generation factor in the cell independent of the voltage. The non-radiative recombination heat and Joule heat depend on voltage. Apart from these bulk heating factors, the surface recombination heat and Peltier heat were also investigated. The surface recombination heat is higher at open-circuited voltage (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 has a small gradient across the cell thickness (<5 × 10 9 W / m 3 ) as the cell is quite thin. However the V oc decreases from 0.54 V to 0.49 V (Δ V = 0.047 V). The temperature shows small gradient across the cell (0.01 K). However, the initial temperature (293 K) increases to 315–320 K during the operation as studied by the coupled study. A higher temperature did not change the J sc but the fill factor decreases from 73.8% to 71.8% and the PCE falls by 11.11% (from initial 12.78%–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. We compared our simulation results with literature data for heat impact on device characteristics of kesterite thin film solar cells. • Five heat generation factors and two heat dissipation factors simulated within CZTSSe solar cells. • Thermalization heat is the dominant heat generation (double times bigger than other factors). • Heat generation is maximum at the CZTSSe/CdS/ZnO junction and is minimum away from junction. • Heat dissipation mainly occurs through convective cooling rather than radiative cooling. • Heat loss causes >11% loss in efficiency mainly by 47 mV loss in open-circuit voltage.