Ligand Homogenized Br–I Wide-Bandgap Perovskites for Efficient NiO_<i>x</i>-Based Inverted Semitransparent and Tandem Solar Cells

Abstract

Phase heterogeneity of bromine-iodine (Br-I) mixed wide-bandgap (WBG) perovskites has detrimental effects on solar cell performance and stability. Here, we report a heterointerface anchoring strategy to homogenize the Br-I distribution and mitigate the segregation of Br-rich WBG-perovskite phases. We find that methoxy-substituted phenyl ethylammonium (<i>x</i>-MeOPEA⁺) ligands not only contribute to the crystal growth with vertical orientation but also promote halide homogenization and defect passivation near the buried perovskite/hole transport layer (HTL) interface as well as reduce trap-mediated recombination. Based on improvements in WBG-perovskite homogeneity and heterointerface contacts, NiO_<i>x</i>-based opaque WBG-perovskite solar cells (WBG-PSCs) achieved impressive open-circuit voltage (<i>V</i>_oc) and fill factor (FF) values of 1.22 V and 83%, respectively. Moreover, semitransparent WBG-PSCs exhibit a PCE of 18.5% (15.4% for the IZO front side) and a high FF of 80.7% (79.4% for the IZO front side) for a designated illumination area (da) of 0.12 cm². Such a strategy further enables 24.3%-efficient two-terminal perovskite/silicon (double-polished) tandem solar cells (da of 1.159 cm²) with a high <i>V</i>_oc of over 1.90 V. The tandem devices also show high operational stability over 1000 h during T₉₀ lifetime measurements.