Dual-passivation buried interface molecular bridges for efficient carbon-based CsPbIxBr3−x perovskite solar cells

Abstract

Despite the advantages of good thermal stability and low cost, CsPbI_xBr_3−x all-inorganic carbon-based perovskite solar cells (C-IPSCs) still experience significant non-radiative recombination at the buried interface between the electron transport layer (ETL) and the perovskite, resulting in substantial energy losses that limit the power conversion efficiency (PCE) of C-IPSCs. Herein, a dual-passivation buried interface molecular bridge was constructed between the SnO₂ and CsPbI_xBr_3−x layers by introducing 1-carboxymethyl-3-methylimidazolium chloride (HOOCMIMCl) to minimize interface defects and reduce non-radiative recombination. The results demonstrated the COOH groups and imidazolium cations in HOOCMIMCl can be simultaneously anchored on the surfaces of SnO₂ and CsPbI_xBr_3−x perovskite layers, effectively passivating oxygen vacancies (V_o) on the SnO₂ surface and the uncoordinated Pb²⁺ in the perovskite film. Meanwhile, after introducing dual-passivation buried interface molecular bridges, the energy barrier between the SnO₂ and CsPbI_xBr_3−x layers was reduced, facilitating rapid carrier transport, while the crystallization of the perovskite film was also promoted, resulting in larger grain sizes and smoother films. In addition, the hydrogen bonding formed between the N–H groups and the CsPbI_xBr_3−x perovskite can suppress I⁻ migration, releasing residual stress and enhancing the stability of the crystal structure. Compared to control CsPbI_xBr_3−x C-IPSCs with a PCE of 12.89% and V_oc of 1.09 V, the champion target C-IPSCs exhibited significantly higher performance, with a PCE of 15.51% and V_oc of 1.19 V. The unencapsulated target C-IPSCs can maintain 82% of their initial PCE after 1000 hours in a low-humidity air environment (T = 25 °C, RH = 20–25%), and 83.5% of the initial PCE after aging 200 hours in an N₂ atmosphere at T = 85 °C.