The oxygen evolution reaction is known to be a kinetic bottleneck for water splitting. Triggering the lattice oxygen oxidation mechanism (LOM) can break the theoretical limit of the conventional adsorbate evolution mechanism and enhance the oxygen evolution reaction kinetics, yet the unsatisfied stability remains a grand challenge. Here, we report a high-entropy MnFeCoNiCu layered double hydroxide decorated with Au single atoms and O vacancies (Au_SA-MnFeCoNiCu LDH), which not only displays a low overpotential of 213 mV at 10 mA cm⁻² and high mass activity of 732.925 A g⁻¹ at 250 mV overpotential in 1.0 M KOH, but also delivers good stability with 700 h of continuous operation at ~100 mA cm⁻². Combining the advanced spectroscopic techniques and density functional theory calculations, it is demonstrated that the synergistic interaction between the incorporated Au single atoms and O vacancies leads to an upshift in the O 2p band and weakens the metal-O bond, thus triggering the LOM, reducing the energy barrier, and boosting the intrinsic activity.

The hole transport layer (HTL)-free carbon-based perovskite solar cells (C-PSCs) are promising for commercialization owing to their excellent operational stability and simple fabrication process. However, the power conversion efficiencies (PCE) of C-PSCs are inferior to the metal electrode-based devices due to their open-circuit voltage (V _oc) loss. Herein, time-resolved confocal photoluminescence microscopy reveals that grain boundary defects at the perovskite/carbon interface are very likely to function as nonradiative recombination centers in HTL-free C-PSCs. A versatile additive Li₂CO₃ is used to modify the conformal tin oxide electron transport layer for HTL-free C-PSCs. Li₂CO₃ modification can result in enhanced charge extraction and optimized energy alignment at electron transport layer/perovskite interface, as well as suppressed defects at perovskite top surface due to Li₂CO₃-induced formation of PbI₂ crystallites. Such dual interfacial passivation ultimately leads to significantly improved V _oc up to 1.142 V, which is comparable to the metal electrode-based devices with HTL. Moreover, a record-high PCE of 33.2% is achieved for Li₂CO₃-modified C-PSCs under weak light illumination conditions, demonstrating excellent indoor photovoltaic performance. This work provides a practical approach to fabricate low-cost, highly efficient carbon-based perovskite solar cells.