Uniform phase distribution of wide bandgap perovskite for high-performance perovskite-silicon tandem solar cells

Metal halide perovskite-silicon tandem solar cells offer a promising pathway towards surpassing the efficiency limits of single-junction devices, and the focus remains on the wide bandgap (WBG) perovskite top cell optimization. Here, by incorporating melamine additive into a rubidium-alloyed perovskite composition, we suppress film phase separation and inhomogeneity and enhance charge carrier mobility. Consequently, our modified 1.68 eV WBG perovskite solar cells exhibit superior charge transport and minimized non-radiative recombination losses, achieving state-of-the-art performance with open circuit voltage (VOC) of 1.31 V, fill factor of 86.4% and efficiency of 25%. This also derives an efficient two-terminal perovskite-silicon tandem cell with stabilized efficiency of 33.5% and high VOC of 2.02 V. Both the single-junction and tandem devices show noticeable operational stability that the WBG cells maintain 80% of initial efficiency (T80) after over 3200 hours of 1-sun illumination under 65°C (ISOS-L-2), while the tandem device survive T90 lifetime exceeding 1100 hours under the same conditions. The underlying strategies to tackle A-site inhomogeneity of Rb-alloyed wide bandgap perovskites remain under investigation. Here, authors incorporate a melamine additive as a phase uniformity regulator, achieving stabilized efficiency of 33.5% for two-terminal perovskite/silicon tandem solar cells.