Perovskite Solar Cells with ZnO-MgO-SnO2 Multilayer Electron Transport Layers

Organic–inorganic hybrid perovskite solar cells (PSCs) have attracted significant attention in recent years due to their exceptionally high theoretical photoelectric conversion efficiency. Although substantial breakthroughs have been made in controlling the bandgap by adjusting the ratio of organic–inorganic compounds, research on the electron transport layer (ETL) and hole transport layer has been largely overlooked, which greatly limits the further development of PSCs. In this study, a multilayer electron transport layer (ETL) was constructed based on ZnO nanofilms, utilizing MgO and SnO₂ with similar lattice dimensions to create a multilayer nanofilm structure. This design achieved energy level alignment, reduced exciton migration energy, and suppressed nonradiative recombination. Compared to the ZnO-SnO₂ bilayer ETL, the ZnO-MgO-SnO₂ multilayer ETL demonstrated a 142% improvement in photoelectric conversion efficiency. Finite element analysis from a microscopic perspective revealed the influence of MgO on carrier concentration. Additionally, first-principles calculations elucidated the transition of MgO from an insulator to a wide-bandgap semiconductor as it transformed from bulk crystal to nanofilm. The ZnO-MgO-SnO₂ multilayer model explained the changes in the energy band structure of the multilayer ETL, providing a theoretical foundation for continuously enhancing the photoelectric conversion efficiency of PSCs.