Environmental Benign Cl‐Terminated MXene For Buried Interface Engineering in Perovskite Solar Modules

Buried interface is imperative to boost charge carrier extraction and optimize interfacial electronic properties in devices, including perovskite solar cells. Cl‐terminated MXene (Ti 3 C 2 Cl x ) is designed and developed via a hydrofluoric acid‐free, environmentally friendly Lewis acid molten salt (LAMS) methodology, and placed it as a buried interfacial layer between the SnO 2 and the perovskite. The formulated MXene forms a stable colloidal suspension in N , N ′‐dimethylpropyleneurea. The Cl terminations available on the MXene surface effectively passivate oxygen vacancy‐related defects in the SnO 2 layer, which advances the interfacial electronic properties. Ti 3 C 2 Cl x as an interlayer facilitates effective charge transport, promotes crystallinity in perovskite, and lowers defect densities. The MXene‐adjusted perovskite solar cells measured a record PCE of 25.75%, with modules reaching 21.88%, besides excellent stability. After 1200 h, the fabricated solar cells retained 95.5% of their initial performance, compared to 76.9% for control devices, endorsing MXene's effectiveness in suppressing interfacial degradation and pushing device longevity.