Photocurrent Loss Analysis of Series Connected Tandem Solar Cells Based on Hybrid Tin Perovskites, Kesterites, and Semiconducting Polymers

Abstract

Series connected tandem solar cells (TSCs) based on low-temperature solution-processable semiconductors such as organic-inorganic hybrid perovskites (OIHPs), kesterites, and polymers have been analyzed optically using the transfer matrix method (TMM). Various active-layer combinations for top and bottom sub-cells have been compared with respect to the maximum possible photocurrent density, parasitic absorption loss, reflection loss, and spectral overlap loss. The choice of materials was such that either their band gaps are close to ideal values or highest efficiency devices were reported using them. In the initial step for device optimization, the thickness of nonactive layer has been optimized to maximize the absorption in the low bandgap sub-cell. Subsequently, thicknesses of both the active layers were simultaneously varied to maximize and match the photocurrent densities ($J_{PH\vert Max}$) in two sub-cells. Within the several combinations optimized, we found that polymer - tin OIHP and all-polymer TSCs were the most promising ones, with $J_{PH\vert Max}$ values of 15.566 and 15.232 mA.cm−2 respectively. While the former had the lowest reflection loss (1.831 mA.cm−2) and spectral overlap loss (1.273 mA.cm−2) respectively, the later had the lowest parasitic absorption loss of 0.487 mA.cm−2. On the other hand, the all-OIHP TSCs analyzed here, were the least promising ones with reflection losses that could be as high as 18.18 mA.cm−2. These results will be useful for the development of efficient and environment friendly tandem solar cells.