Metal halide inorganic perovskites with excellent thermal stability and ideal bandgaps are suitable for constructing inverted top subcells for tandem devices. However, facts such as defect-induced nonradiative recombination, interfacial energy level mismatch, and halide ion migration hinder further development of high-performance inorganic perovskite solar cells (PSCs). Herein, we use trivalent cation ytterbium (Yb3+) as a modifier for post-treatment of inorganic perovskite surfaces to fabricate highly efficient and stable inorganic PSCs. The incorporation of Yb3+ is found to alleviate strain tension on perovskite surface region. On the one hand, Yb3+ ions assist to form a back-surface electric field, align energy levels and suppress non-radiative recombination of carriers; on the other hand, Yb3+ ions strongly interact with iodide, which reduces interfacial defects and prohibits iodide migration. Ultimately, the efficiency of the inverted CsPbI3-xBrx inorganic PSCs is enhanced from 19.3% to 21.4%, with open circuit voltage increasing from 1.151 V to 1.256 V. Impressively, the Yb3+-treated PSCs show excellent ambient and operational stabilities, by exhibiting only 10% degradation for 1260 h under maximum power point tracking and continuous one sun irradiation. This work emphasizes the importance of interfacial engineering by high-valence cations for improving the performance of inverted inorganic PSCs.