Efficient and Stable Inverted Perovskite Solar Cell with 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. A novel solution-processed cathode interlayer material, surfactant encapsulated polyoxometalate complex [(C8H17)4N]4[SiW12O40] (TOASiW12) is employed to modify 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 TOASiW12 layer can effectively obstruct the chemical reaction between Al and perovskite layer, and significantly enhance the device stability. The unencapsulated devices with TOASiW12-modified Al retain more than 80% of the initial PCE after 350 h storage in the ambient atmosphere at 45% relative humidity. This work provides an alternative cathode interlayer material for efficient and stable inverted PVSCs.