Sulfadiazine Interface Layer-Multisite Passivation and Energy Level Regulation for Inverted Perovskite Solar Cells

Self-assembled molecules (SAMs) are widely used as hole-selective layers (HSLs) in inverted perovskite solar cells (PSCs). However, its uneven film formation and limited passivation ability for buried interface defects hinder further improvements in device performance. This work introduces sulfadiazine (SD), which contains multifunctional groups, as the interface layer between [2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic acid (MeO-2PACz) and perovskite layers. The SD molecules enhance carrier transport through π-π interactions with the MeO-2PACz. And also, SD also achieves improved energy level alignment, facilitating the transfer of holes at the interface. The N atom on the pyrimidine ring and the O atom in the sulfonamide group of SD can coordinate and bind with Pb²⁺ ions. Additionally, the N atom in the -NH₂ group can form hydrogen bonds (N-H···N) with the FA⁺ ions in the perovskite. The multisite passivation effect significantly reduces nonradiative recombination losses in the device. As a result, devices utilizing SD to modify buried interfaces have achieved a power conversion efficiency (PCE) of 23.27%. Furthermore, the target devices demonstrate excellent thermal stability. This study indicates that using SD as an interface layer is an effective strategy for enhancing the efficiency and stability of PSCs.