Imaging-Based Loss-Analysis for Perovskite/Perovskite/Silicon Triple-Junction Solar Cells

Perovskite/perovskite/silicon triple-junction solar cells promise to harvest electricity from the sunlight more efficiently than single- or dual-junction solar cells. However, with an increasing number of functional layers, it becomes more and more complex to disentangle from which layer a defect originates from. Imaging-based techniques can help to localize defects that lead to electrical losses due to their spatial resolution and subcell selectivity of some of the methods. In this work, we give an overview of imaging-based measurement techniques that can be used to analyze various kinds of defects. The homogeneity of the absorber layers can be investigated independently from each other, using subcell-selective photoluminescence (PL) imaging. Combining PL imaging with electroluminescence (EL) imaging, the homogeneity of electron and hole transport layers can be evaluated. Shunts can be located and attributed to subcells in the triple-junction solar cell by applying dark and illuminated lock-in thermography. Voltage and selectivity losses can be investigated subcell-resolved with a combination of terminal voltage measurements and PL based implied open-circuit voltage (iVOC) imaging. As an exemplary application, this work demonstrates that significant transient changes can be revealed tracking the terminal voltage, the iVOC, and the resulting selectivity losses during a light soaking procedure. As we demonstrate, combining the set of possible measurements discussed in this work allows for a comprehensive investigation of electrical losses which is a fundamental prerequisite to unlock the power conversion potential of perovskite/perovskite/silicon triple-junction solar cells.