Atomic Layer Deposited ZnO–SnO2 Electron Transport Bilayer for Wide‐Bandgap Perovskite Solar Cells

High‐quality electron transport layer (ETL) is a prerequisite for high‐performance wide‐bandgap mixed‐halide perovskite solar cells (PSCs), which is critical for efficient perovskite/silicon tandem solar cells. Herein, an atomic layer deposited ZnO–SnO 2 bilayer ETL for wide‐bandgap PSCs is reported, featuring a high uniformity and conformality over a large area. The ZnO–SnO 2 bilayer shows a matched band alignment with wide‐bandgap perovskite for efficient electron extraction and transport, with a lower nonradiative recombination. As a result, a champion power conversion efficiency of 18.1% is achieved on the ZnO–SnO 2 bilayer‐based wide‐bandgap PSCs featuring an ultrahigh open‐circuit voltage ( V oc ) of 1.233 V, which is the highest value for wide‐bandgap PSCs without any surface passivation. In addition, the atomic layer deposition ZnO–SnO 2 bilayer exhibits very good surface passivation and conformality on crystalline silicon surfaces, which makes it attractive to be applied for perovskite/silicon tandem solar cells with a higher V oc and textured surfaces.