Abstract: Carbon-based hole-transport-layer-free CsPbI₂Br perovskite solar cells have attracted widespread attention owing to their low fabrication cost and excellent thermal stability. However， the rapid crystallization of CsPbI₂Br films often leads to a high density of defects， resulting in trap-assisted non-radiative recombination and severe ion migration， which significantly accelerate energy losses and performance degradation of the devices. In this study， a simple and practical additive strategy was adopted to regulate the crystallization and passivate defects in CsPbI₂Br using the synergistic effects of anions （4Cl-BZS^-） and cations （Na⁺） from sodium 4-chlorobenzenesulfonate （Na-4Cl-BZS）. The 4Cl-BZS^- anions coordinate with Pb²⁺ through the —SO₃^- and —Cl functional groups located at both ends of the benzene ring， effectively passivating under-coordinated Pb²⁺ and increasing the formation energy of halide vacancies. This interaction also promotes preferential growth of the perovskite polycrystalline film along the （100） plane， yielding high-quality CsPbI₂Br films. Moreover， Na⁺ cations incorporate into the perovskite lattice via interstitial doping， significantly increasing the migration barrier of halide ions and enhancing the crystal stability of the perovskite. Benefiting from the cooperative action of the cation-anion pair， the resulting carbon-based hole-transport-layer-free CsPbI₂Br perovskite solar cell achieves a power conversion efficiency of 13.07%， along with an open-circuit voltage of 1.18 V and a fill factor of 74.26%.

Key words: all-inorganic perovskite solar cell; CsPbI₂Br perovskite; additive engineering; crystallization regulation; defect passivation; first-principle calculation