Comprehensive device simulation of 16.9% efficient two-terminal PbS–PbS CQD tandem solar cell

The significant losses that limit the efficiency of a single-junction solar cell are thermalization loss and transmission loss. Thus, to efficiently utilize the solar spectrum and mitigate these losses, tandem solar cells (TSCs) have significantly impacted the photovoltaic (PV) landscape. In this context, the research on perovskite/silicon tandems is currently dominating the research community. However, challenges such as stability of perovskite, pin-hole defects, conformal deposition of perovskite over textured silicon, the low absorption coefficient of silicon, and high module cost of the bottom subcell are the tailback for its mass production at the industrial level. Therefore, considering the detailed balance limit for the TSC, a low-cost solution-processed top and bottom subcells with a tunable bandgap can be well thought for the low-cost tandem design. Thus, here in this work, two different PbS–PbS colloidal quantum dot (CQD) TSCs with a conversion efficiency of 15.6% and 16.9% are proposed through comprehensive device simulations. Three different PbS-CQDs with a bandgap of 1.14eV, 1.45eV, and 1.56eV are utilized to design the TSCs under consideration. Detailed standalone and tandem analysis has been carried out in terms of absorber layer thickness variation, filtered spectrum, filtered integrated power, current matching, tandem current density voltage (J-V) curves, and tandem PV parameter to finalize the conversion efficiency. The filtered spectrums are obtained by using the transfer matrix method to account for the interfacial reflection losses and thin-film interference effects. The tandem device constructed using 1.45eV and 1.56eV based top subcell showed the open-circuit voltage VOC of as high as 1.71V and 1.83V, respectively. The comprehensive theoretical analysis of PbS–PbS CQD tandem devices proposed in this work may pave the way for developing high-efficiency TSCs for low-cost applications.