Optimization of a Pb-free all-perovskite tandem solar cell with 30.85% efficiency
Published in Optical Materials, 2022
In this study, the numerical simulation of a monolithic 2-terminal allperovskite tandem solar cell has been analyzed. The electron affinity of the electron and hole transport layers, the cross-section of defects, and the thickness of each component were varied using the SCAPS-1D solar cell simulator to understand their effect on the PCE. The simulation of the tandem device was done with the bottom subcell being illuminated with the light filtered by the top subcell, thus ensuring a realistic analysis. Given the current matching condition, our simulation results showed that the JSC of the tandem device is limited by the JSC of the bottom subcell. Thinning of the top subcell is necessary to match the current across the device. While the JSC of the tandem device is smaller than the currents of the optimized individual subcells, a high VOC of 2.63 V in the tandem device results in a significantly higher PCE of 30.85% compared to that of individual subcells.
The optimal thickness of the subcells found was 1.6 μm and 983 nm. The calculated PCE for those thicknesses will be higher than experi mental values, given that the calculations consider only the dominant scattering channel, trap defects at the interface, and ignore scattering at grain boundaries. However, if we reduce the thickness of both cells to be below 1 μm, we still see a large PCE. For instance, when the thickness of the FASnI3 is set to 1 μm, the current matching condition requires the layer MAGeI3 to be 961 nm and the results we obtain are that the JSC is 14.6 mA/cm2, VOC is 2.63 V, FF is 80%, and PCE is reduced from the optimal 30.85% to 30.73%. Overall, these results suggest that lead-free perovskites can compete with lead-based devices in all-perovskite tan dem solar cells. Further improvement in the performance of the tandem device can be achieved by utilizing a bottom subcell that can provide higher JSC.
Recommended citation: Duha, Arman U., and Mario F. Borunda. "Optimization of a Pb-free all-perovskite tandem solar cell with 30.85% efficiency." Optical Materials 123 (2022): 111891.
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