Ultralow-Cost Lacunary Metal-Oxo Framework Enables Efficient and Stable Organic Solar Cells

Organic solar cells (OSCs) with p-i-n architecture usually exhibit decent efficiency due to the easily tunable energy levels of organic interfacial layers (ILs). However, their operational lifetime is limited by the morphological instability of organic ILs especially the electron-transporting layer (ETL) that shows strong self-aggregation tendency. Besides, organic ETLs are confronted with significant challenges including large batch-to-batch variations and high costs. Herein, we develop an inorganic lacunary-structure metal-oxo framework as ETL of p-i-n OSCs. The resultant molecule, BSiW₉, not only shows ultralow cost but also leads to significantly enhanced electron extraction in OSCs. Moreover, the redox activity of BSiW₉ allows reinforced electrical conductivity by using a hydroquinone-derivative dopant, HQ. The doping strategy finally results in a remarkable PCE of 20.5% in p-i-n OSC, largely outperforming that using organic ETLs. Meanwhile, an outstanding long-term stability is obtained in this champion device, with 92% of original efficiency maintained after a maximum-power-point tracking for 1250 h, among the longest lifetimes of p-i-n OSCs. This work demonstrates the effectiveness of utilizing rationally tailored low-cost metal-oxo framework as ILs for more industrially compatible OSCs.