Absolute Photoluminescence Measurements for Sub-Cell Characterization of Perovskite Multijunction Solar Cells

Mixed-halide perovskites have emerged as promising semiconductors for next-generation solar cells, particularly in multijunction architectures. These multijunction perovskite solar cells can significantly enhance efficiency by optimizing the balance between thermalization and absorption losses compared to traditional single-junction cells. However, their performance is often limited by open-circuit voltage (Voc) losses, primarily due to non-radiative recombination processes in both tandem and single-junction configurations.

In this study, we systematically investigate the role of defects and their passivation in influencing non-radiative recombination in mixed-halide perovskite solar cells, considering both tandem and single-junction setups. We utilize absolute photoluminescence (PL) measurements to assess the quasi-Fermi level splitting (QFLS) in perovskite layers, both with and without charge transport layers, to distinguish between bulk and interfacial contributions to recombination. This approach enables a direct evaluation of the factors limiting the radiative Voc, driving improvements in both cell types.

Furthermore, sub-cell-selective absolute PL measurements allow us to precisely analyze the QFLS in each absorber layer within the tandem configuration, facilitating a comprehensive comparison between the sub-cells. By reconstructing the current-voltage (J−V) characteristics based on these individual QFLS assessments, we isolate the impacts of charge transport losses and finite ideality factors. Our findings identify the key performance-limiting factors in tandem solar cells after prolonged operation, highlighting potential pathways to mitigate these losses.

This work provides new insights into the intrinsic and extrinsic factors affecting mixed-halide perovskite multijunction solar cell efficiency, offering valuable strategies for developing more efficient and durable photovoltaic technologies.