Efficient and Stable Inverted Perovskite Solar Cells with TOASiW 12 ‐Modified Al as a Cathode

Inexpensive metal Al is scarcely utilized as the cathode in the perovskite solar cells (PVSCs) because its violent reaction with perovskite active layer results in poor device stability in air. It is urgent to improve the efficiency and stability of PVSCs with Al as the cathode for mass production of low‐cost PVSCs. Herein, a novel solution‐processed cathode interlayer material, surfactant‐encapsulated polyoxometalate complex [(C 8 H 17 ) 4 N] 4 [SiW 12 O 40 ] (TOASiW 12 ) is reported. Using TOASiW 12 ‐modified Al as the cathode, the power conversion efficiency (PCE) of 20.64% has been achieved in the inverted PVSCs. The findings demonstrate that a thin TOASiW 12 layer can effectively obstruct the chemical reaction between Al and perovskite layer, and significantly enhance the device stability. The unencapsulated devices with TOASiW 12 ‐modified Al retain more than 80% of the initial PCE after 350 h storage in the ambient atmosphere at 45% relative humidity. This study provides an excellent alternative cathode interlayer material for efficient and stable inverted PVSCs.