Monolithic Tandem Solar Cell With Co-Sensitized DSSC and Perovskite Sub-Cells Using Spectral Filtering for High-Efficiency Photon Management

Recent advances in dye-sensitized and perovskite solar technologies have enabled tandem architectures to surpass single-junction efficiency limits. This work reports a high-efficiency monolithic tandem solar cell combining a co-sensitized dye-sensitized solar cell (DSSC) top sub-cell with a triple-cation perovskite bottom sub-cell. The DSSC, based on a mesoporous TiO₂ photoanode co-sensitized with SM315 and ZnTPP dyes, harvests light from 400 to 650 nm. The bottom cell, using a Cs/FA/MA mixed-halide perovskite, targets near-infrared photons (650–850 nm). A dielectric multilayer optical filter facilitates spectral splitting, while a thin indium tin oxide recombination layer ensures efficient series connection and current matching. Under calibrated dual-LED illumination (∼125 mW/cm²), the tandem achieved a lab-measured power conversion efficiency (PCE) of 33.7%, with a simulated maximum of ∼36.8% and an average reproducible PCE of 33.2% ± 0.4% (n = 3). When tested under a class AAA AM1.5G solar simulator (100 mW/cm²), the device produced a baseline PCE of 27.1% (short-circuit current density, J_SC = 16.1 mA/cm², open-circuit voltage, V_OC = 1.95 V, fill factor, FF = 0.72). These values are in-house laboratory results, not certified records. UV–Vis, FTIR, external quantum efficiency, and EIS confirmed effective charge transport and spectral complementarity. Surface and interface morphology were characterized by AFM, SEM, and HRTEM. Stability testing showed > 96% retention after 500 h at 25°C and ∼86% at 60°C. Outdoor field testing under tropical weather confirmed functional robustness. This scalable, solution-processed tandem architecture shows promise for next-generation photovoltaics, including building-integrated and indoor energy applications.