Ethacridine lactate additive engineering for defect passivation in HTL-free carbon electrode perovskite solar cells

Hole-transport-layer (HTL)-free carbon electrode perovskite solar cells (C-PSCs) are promising candidates for low-cost photovoltaic applications, but their performance is still limited by defect-induced recombination and insufficient long-term stability. Herein, ethacridine lactate (EAL) is employed as a multifunctional additive in the perovskite precursor solution to regulate film quality and interfacial properties. Owing to the presence of a carboxyl group in the lactate anion and two amino groups in the ethacridine cation, EAL interacts with undercoordinated Pb 2+ and dangling I − species, which stabilizes the perovskite structure and promotes charge transport across the perovskite/carbon interface. Consequently, the EAL-modified films show improved morphology and reduced defect density, resulting in enhanced photovoltaic performance. The optimized device delivers a power conversion efficiency of 16.54% and retains 80% of its initial efficiency after 1200 h without encapsulation. This work highlights an effective additive-engineering strategy for achieving efficient and stable HTL-free carbon electrode PSCs.