In Situ Formation of Ag2MoO4 in a Ag/MoO3 Buffer Layer Enables Highly Efficient Inverted Perovskite Cell for a Tandem Structure

The tandem structure using perovskite front cells is a very promising strategy to overcome the Shockley–Queisser limit. The transparency of the front cell window layer is the key to maximize incident light utilization efficiency. A buffer layer is required to prevent the organic materials from sputtering damage when conducting metal oxides are used as the window layer. Here, we report a combination of Ag (1 nm) and MoO3 (3 nm) as a buffer layer to fabricate a highly efficient inverted perovskite front cell. Characterizations show MoO3 reacts with predeposited Ag and forms Ag2MoO4, resulting in a dense, continuous, and uniform protection layer. Importantly, the intrinsic electron-transport property and matched energy levels of Ag2MoO4 with adjacent layer materials greatly improve charge carrier collection efficiency, resulting in a 65% enhancement in efficiency compared to the Ag-only buffer layer. Our results demonstrate that the in situ reaction of an oxide with a metal is a simple strategy to build functional ultrathin films.