Quantifying the Spatial Distribution of Series Resistance in Monolithic Perovskite/Silicon Tandem Solar Cells Using Voltage-Dependent Photoluminescence Imaging

To enhance the performance of monolithic perovskite/silicon tandem solar cells toward their theoretical limits and enable commercial-scale deployment, it is essential to quantify local power losses and identify their physical origins. In this study, we apply a method to extract the local tandem series resistance (LTRS), a key contributor to the performance degradation of perovskite/silicon tandem devices. The method is based on bias-voltage-dependent photoluminescence (PL) imaging under two different illumination intensities, coupled with the generalized Planck's law. Finite element simulations demonstrate the robustness of the method under a range of realistic conditions, including current mismatch, low shunt resistance, and luminescence coupling effects. When exemplarily applied to a high-efficiency perovskite/silicon tandem device with a power conversion efficiency PCE of 29%, the method reveals that approximately 1.9% absolute efficiency loss can be attributed to resistive effects. We further investigate the influence of the transient behavior of perovskites on LTRS measurements using a metastable device. The results show that, even for unstable samples, reliable estimations of LTRS can be achieved if an appropriate stabilization protocol is employed. These findings establish PL imaging as a powerful diagnostic tool for identifying performance-limiting regions and guiding the design and processing improvements of next-generation tandem photovoltaics.