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Perovskite solar cells (pero-SCs) containing lithium bis(trifluoromethane)sulfonimide (LiTFSI)-doped Spiro-OMeTAD-based hole transport layers (HTLs) exhibit outstanding power conversion efficiencies (PCEs). However, the dopant LiTFSI likely causes a severe morphology change and induces ion migration, which can also corrode the underlying perovskite film, owing to its hygroscopicity and small ionic radius. In this study, we developed a Spiro-OMeTAD-like organic salt (Spiro-BD-T) with a large-size cation composed of a Spirobifluorene (Spiro) backbone and phenylpyridin-4-amine (BD) as well as an anion composed of TFSI-. The anion in Spiro-BD-T can promote the oxidation of Spiro-OMeTAD and effectively form a weakly bound Spiro-OMeTAD•+TFSI− system. Moreover, the Spiro-OMeTAD-like cation in Spiro-BD-T exhibits good miscibility with Spiro-OMeTAD, excellent hydrophobicity and does not easily migrate, which diminishes the ingress of humidity and eliminates the detrimental Li+ migration. Ultimately, the Spiro-BD-T-doped Spiro-OMeTAD HTL showed a homogeneous and pinhole-free morphology with improved composition stability. The resultant pero-SCs exhibited an excellent PCE of 24.2% with significantly promoted long-term stability. [Display omitted] • Spiro-BD-T enables to sufficiently promote the oxidation of Spiro-OMeTAD, resulting in an increase in hole density. • Spiro-BD-T can diminish the ingress of humidity, passivate uncoordinated Pb2+ and eliminate the detrimental Li+ migration. • The backbone of Spiro-BD-T is similar to Spiro-OMeTAD, which is beneficial for increasing its miscibility. [ABSTRACT FROM AUTHOR]

Solution-processed perovskite films have high trap densities especially on the perovskite surface that become pathways of moisture invasion, unavoidably leading to perovskite degradation. Although the water resistance or crosslinking organic molecules attached to the perovskite film can partially mitigate the degradation, there is usually a significant trade-off between device power conversion efficiency (PCE) and moisture stability due to the insulating nature of the organic molecules. Here, we designed and synthesized a cross-linkable molecule PETA-G to solve the problem by rationally combining the guanidine and tri-acrylate groups. The guanidine group with three lone pair electrons enables sufficient bonding between lone pair electrons and undercoordinated Pb2+ of the perovskite grain surface; the tri-acrylate group with three crosslink sites has a moderate crosslinking condition that can spatially crosslink, thus forming a compact network on the perovskite surface. The crosslinked PETA-G (CL-PETA-G) can significantly suppress non-radiative recombination and improve the moisture resistance of the perovskite film that even survives when dipped into water, while the charge transport was not influenced. Consequently, the long-term moisture and operational stabilities of the perovskite solar cells based on FA 0.92 MA 0.08 PbI 3 with CL-PETA-G were dramatically increased, and the devices achieved a remarkable PCE as high as 22.6%. We synthesized a cross-linkable molecule PETA-G combining the guanidine and tri-acrylate groups, which can spatially crosslink on the perovskite film to improve the moisture-resistance ability and passivate surface defects of perovskite film. [Display omitted] • PETA-G can crosslink a framework in spatial dimension with high crosslinking degree on perovskite film. • The crosslinking framework improves the water-resistance ability of perovskite film even immersing into water. • PETA-G can repair the perovskite film morphology and electronic defects. [ABSTRACT FROM AUTHOR]