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-SnO2 bilayer ETL for wide-bandgap PSCs is reported, featuring a high uniformity and conformality over a large area. The ZnO-SnO2 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-SnO2 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-SnO2 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.