Four‐Terminal Tandem Based on a PM6:L8‐BO Transparent Solar Cell and a 7 nm Ag Layer Intermediate Electrode

To overcome transmission and thermalization losses from single‐junction solar cells, the two‐terminal tandem cell configuration is one of the most widely followed approaches. Unfortunately, the need to match the current from both cells, in addition to the fabrication of an interlayer with excellent optical and electronic performances, makes such two‐terminal configurations a challenging approach. Herein, the fabrication of a four‐terminal tandem incorporating a front transparent cell made using a 7 nm Ag back electrode and a PM6:L8‐BO blend which exhibits a bandgap close to the optimal according to the detailed balance theory is reported. For the opaque back cell in such tandem, a PTB7‐Th:O6T‐4F blend is used. A 16.94% power conversion efficiency is achieved when such two cells are configured in a four‐terminal device separated by a WO ₃ /LiF/WO ₃ multilayer providing an optimal light absorption distribution among the two cells.