Tailoring Molecular Conjugation Size for Efficient Defect Passivation in Perovskite Photovoltaics

Film surface defects impede the performance of perovskite solar cells. Conjugated molecules with electron-donating/withdrawing groups have demonstrated efficacy in passivating these defects. However, the influence of the conjugated backbone on the passivation state of functional groups has remained insufficiently explored. In this study, we investigated the passivation effectiveness of C═O and N–H groups in different conjugated environments using 2,3-dihydroquinolin-4(1H)-one (DQLO), quinolin-4(1H)-one (QLO), and acridin-9(10H)-one (ADO). Our findings revealed that underconjugated DQLO failed to passivate and even diminished the device performance. Conversely, the larger conjugated ADO led to an averaged electron density distribution and self-aggregation, reducing passivation effectiveness. Optimal passivation was achieved with QLO, resulting in a power conversion efficiency of 23.05% and enhanced stability, retaining 89.0% of initial performance after 1050 h at 30% R.H. and 92.1% after 230 h at 70 °C in N₂. This research underscores the crucial role of conjugated backbones in enhancing the molecular passivation efficiency.