Photostable wide-bandgap perovskites with enhanced interface coupling for all-perovskite tandems

Abstract

Iodide-bromide mixed wide-bandgap perovskite is prone to halide segregation, particularly near the buried interface in solar cell devices, where the illumination, thermal, and electric field stresses are most intense during operation. However, the commonly used molecular substrates, carbazole-based self-assembled monolayers (SAMs), provide only limited chemical interaction with the perovskite lattice, resulting in structural instability and inefficient charge extraction. Here, we introduce a molecular bridging agent that simultaneously conjugates with the SAM substrate and coordinates to the perovskite surface, thereby reinforcing the chemical and electronic coupling across the hole-collecting heterointerface. Through this approach, photostable 1.76 eV perovskite absorbers with enhanced optoelectronic properties and lattice stability were obtained, enabling single-junction perovskite solar cells to achieve a PCE of 20.79% (certified 20.35%). When integrated with a 1.25 eV Sn-Pb perovskite bottom cell, the resulting two-terminal monolithic all-perovskite tandem solar cells delivered an efficiency of 29.58%, and the encapsulated device retained 90% of its peak efficiency after 613 hours of continuous maximum power point operation.