Investigation of Perovskite Solar Cells via a Multi-functional Columnar Cucurbituril Additive Strategy

Organic-inorganic hybrid perovskite solar cells have been lauded as the new hope in the photovoltaic field due to their rapidly increasing efficiency surpassing that of crystalline silicon cells and their cost-effective fabrication. However, they face significant limitations in device performance and long-term stability because the solution-processed polycrystalline films suffer from poor crystallization quality and a high density of defect states. To address this, columnar-structured cucurbit[6]uril (CB[6]) was innovatively introduced as an additive into the perovskite precursor to modulate the crystallization quality of perovskite and passivate internal defects, thereby enhancing the efficiency and stability of devices. The introduction of CB[6] not only promotes uniform grain growth and yields larger-sized perovskite grains with fewer grain boundaries, but also forms multidentate anchoring with uncoordinated Pb²⁺ at grain boundaries/interfaces via Lewis acid-base interactions through its carbonyl-rich ports on the pillared framework, thereby passivating internal defects, stabilizing crystal structure, and suppressing non-radiative recombination. Additionally, stability of the perovskite phase is also improved by blocking ion migration pathways as a result of the suppression of defect generation. Based on this optimization, the n-i-p type devices achieve a power conversion efficiency improvement from 22.92% to 25.14%. Moreover, the hydrophobic cavity of CB[6] enables unencapsulated devices to retain 80.9% of their initial efficiency after continuous aging for 800 hours under conditions of 25 ℃ and 50 ± 5% relative humidity. This study offers valuable insights into defect regulation and stability enhancement of perovskite solar cells.