Polyoxometalate-Based Inorganic–Organic Hybrid [Cu(phen)₂]₂[(α-Mo₈O₂₆)]: A New Additive to Spiro-OMeTAD for Efficient and Stable Perovskite Solar Cells

It is quite meaningful for improving the properties of Spiro-OMeTAD-based hole transport materials (HTMs) to realize high-efficiency and stable perovskite solar cells. In this work, a polyoxometalate (POM)-based inorganic–organic hybrid [Cu(phen)2]2[(α-Mo8O26)](CMP) with strong electron-accepting properties was successfully synthesized and for the first time introduced into Spiro-OMeTAD to achieve quantitative and controllable oxidation of Spiro-OMeTAD, which presents obviously increased conductivity in comparison to its counterpart. Accordingly, the corresponding perovskite solar cells’ (PSCs) performance shows a substantial improvement. The optimal device achieves a power conversion efficiency (PCE) as high as 18.72%, which is higher than that of the ever-reported POMs-based PSCs. Meanwhile, CMP-based PSCs also show long-term stability. This work provides a feasible and efficient approach for further development of PSCs.