This study presents 1,1′-bis(3-sulfonatopropyl)-viologen (BSP-Vi) as a multifunctional interlayer between TiO2 and CsPbI3 in an inorganic perovskite solar cell, enabling dual-interfacial defect passivation and energy-level tuning. BSP-Vi facilitates carrier extraction, improves device efficiency, and suppresses defect-induced degradation, leading to a significantly enhanced operational stability. The potential of viologen-based molecule is highlighted to advance the performance and stability of perovskite solar cells.
The stability and efficiency of inorganic perovskite solar cells (PSCs) remain limited owing to the presence of interfacial and bulk-related defects. To address this issue, a multifunctional defect-passivating interlayer can be introduced. In this study, 1,1′-bis(3-sulfonatopropyl)-viologen (BSP-Vi) was synthesized for depositing a multifunctional interlayer between a TiO2 electron transport layer (ETL) and CsPbI3 perovskite absorber. The sulfonate group in BSP-Vi effectively interacts with both oxygen vacancies on the TiO2 surface and undercoordinated Pb2+ species in the perovskite, leading to substantial defect passivation in both the ETL and perovskite absorber. BSP-Vi induces a favorable shift in interfacial energy levels and facilitates the formation of a perovskite film with improved crystallinity and reduced defect density. Consequently, the optimized PSC incorporating 0.2 wt% BSP-Vi achieves a power conversion efficiency (PCE) of 16.93%, representing a marked increase from that of the control (PCE = 16.08%). The maximum power point tracking test demonstrates that the PSC with BSP-Vi-treated interlayer maintained 95% of the initial performance after 160 h of continuous operation. This study highlights the potential of introducing sulfonate-group-based materials at the ETL/perovskite interface as a promising route to simultaneously passivate defects in and enhance the efficiency and stability of inorganic perovskite photovoltaic devices.
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