Interfacial engineering with trivalent cations for efficient and stable inverted inorganic perovskite solar cells

Abstract

Metal halide inorganic perovskites with excellent thermal stability and ideal bandgaps are suitable for constructing inverted-top subcells for tandem devices. However, factors such as defect-induced nonradiative recombination, interfacial energy level mismatch, and halide ion migration hinder the 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 the perovskite surface region. On the one hand, Yb³⁺ ions assist in forming a back-surface electric field, aligning energy levels and suppressing 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 CsPbI_3−xBr_x inorganic PSCs is enhanced from 19.3% to 21.4%, with the 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 using high-valence cations for improving the performance of inverted inorganic PSCs.