Monolithic All-Perovskite Triple-Junction Solar Cells with Suppressed Non-Radiative and Optical Losses

Multijunction solar cells represent an effective approach to surpassing the ~33% power conversion efficiency limit of ideal single-junction devices by paring multiple absorber layers with cascaded bandgaps. Optical simulations suggest that monolithic all-perovskite triple-junction solar cell comprising 2.0 eV, 1.5 eV, and 1.2 eV perovskite absorbers has the potential to reach a high efficiency of 36.6%. Reducing <i>V</i>_oc-to-bandgap loss in the wide-bandgap sub-cell and enhancing optical response in the narrow-bandgap sub-cell are key to the performance of such devices.<br/><br/>In this contribution, we report effective strategies to manipulate defects at the buried and top interfaces of wide-bandgap perovskites. A dual surface treatment technique helps reduce the non-radiative recombination losses at the perovskite/charge transport layer heterojunctions, yielding a high open-circuit voltage of over 1.4 V and fill factor of 85% with a 1.98 eV perovskite absorber. Furthermore, an optically benign transparent electrode significantly improves near-infrared absorption in the 1.2 eV narrow-bandgap perovskite sub-cell, resulting in current-matched triple-junction solar cells with a short-circuit current density of over 10 mA cm^-2. After optimization, we demonstrate efficient all-perovskite triple-junction solar cells with power conversion efficiencies of over 26%.