Spectral Splitting Solar Cells Combining Planar Heterojunction Wide-Bandgap and Inverted Narrow-Bandgap Perovskite Architectures

Bandgap-tunable perovskite solar cells (PSCs) are highly advantageous for constructing multijunction solar cells. Among these, double-junction four-terminal (4-T) solar cells offer significant benefits due to the absence of constraints related to current matching or the structural integration of top and bottom cells, making them an effective approach for achieving higher efficiencies. In this study, a spectral splitting system was investigated to optimize the performance of 4-T solar cells. The system incorporated a Pb-based PSC with a planar heterojunction structure as the top cell, paired with a SnPb-based PSC with an inverted structure as the bottom cell. Spectral splitting was examined across five discrete wavelengths within the 700–850 nm range to identify the optimal splitting wavelength for maximizing power conversion efficiency (PCE). Ultimately, the 4-T system achieved a peak PCE of 27.8% when employing spectral splitting at 775 and 785 nm.