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

ABSTRACT 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 (LTR _S ), 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 LTR _S measurements using a metastable device. The results show that, even for unstable samples, reliable estimations of LTR _S 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.