Outdoor measurements of a full-size bifacial Pero/Si tandem module under different spectral conditions

In recent years, significant progress has been made in terms of efficiency and stability of perovskite on silicon (Pero/Si) tandem solar cells. Nevertheless, most of these activities are focused on small-area laboratory cells while the availability of large-area solar cells suitable for module integration on an industrial level remains limited, and therefore, measurements of tandem modules are rare. However, the reliable measurement of tandem modules is a prerequisite to evaluate the real potential of this rapidly developing technology for the photovoltaic market. In this study, we present the first published outdoor measurement of a full-size bifacial Pero/Si tandem solar cell module. Our focus is on analyzing the spectral influences on the outdoor performance of the device through a qualitative assessment of the modules I-V parameter conducted over the course of a measurement day. Based on continuous monitoring of the ambient and module conditions, we provide consistent explanations for the complex interplay between the incident irradiance on both the front and backside of the module, as well as the module temperature. Based on our findings, we finally discuss how to appropriately account for the influence of bifaciality in the case of bifacial tandem modules, where the procedures used for bifacial single-junction devices cannot be easily applied due to subcell limitation effects. Throughout the study, we present important insights into the real-world characteristics of a bifacial Pero/Si tandem model, discuss and explain various influences on the modules performance, and therefore provide crucial information for an optimal cell design for bifacial Pero/Si tandem devices.