Poly(N,N′-bis-4-butylphenyl-N,N′-bisphenyl)benzidine-Based Interfacial Passivation Strategy Promoting Efficiency and Operational Stability of Perovskite Solar Cells in Regular Architecture

The failure of perovskite solar cells (PSCs) to maintain their maximum efficiency over a prolonged time is due to the deterioration of the light harvesting material under environmental factors such as humidity, heat, and light. Systematically elucidating and eliminating such degradation pathways are critical to imminent commercial use of this technology. Here, a straightforward approach is introduced to reduce the level of defect-states present at the perovskite and hole transporting layer interface by treating the various perovskite surfaces with poly(N,N '-bis-4-butylphenyl-N,N '-bisphenyl)benzidine (polyTPD) molecules. This strategy significantly suppresses the defect-mediated non-radiative recombination in the ensuing devices and prevents the penetration of degrading agents into the inner layers by passivating the perovskite surface and grain boundaries. Suppressed non-radiative recombination and improved interfacial hole extraction result in PSCs with stabilized efficiency exceeding 21% with negligible hysteresis (approximate to 19.1% for control device). Moreover, ultra-hydrophobic polyTPD passivant considerably alleviates moisture penetration, showing approximate to 91% retention of initial efficiencies after 300 h storage at high relative humidity of 80%. Similarly, passivated device retains 94% of its initial efficiency after 800 h under operational conditions (maximum power point tracking under continuous illumination at 60 degrees C). In addition to interfacial passivation function, hole-selective role of dopant-free polyTPD is also evaluated and discussed in this study.

Automated summary

The study addresses the issue of degradation in perovskite solar cells (PSCs) over time, caused by environmental factors such as humidity, heat, and light. By treating the perovskite surfaces with polyTPD molecules, the research significantly suppresses defect-mediated non-radiative recombination in PSCs, resulting in improved efficiency and stability. The ultra-hydrophobic polyTPD passivant also helps to prevent moisture penetration, leading to a high retention of initial efficiencies after storage and operational conditions.