Iodine-doped g-C₃N₄ modified zinc titanate electron transporting layer for highly efficient perovskite solar cells

The development of excellent ternary metal oxides as electron transporting layers (ETLs) is highly challenging for perovskite solar cells (PSCs). In this study, ZnTiO₃ (ZTO) nanoparticles are synthesized via a facile sol-gel method, and used as an ETL in PSCs. Furthermore, for the first time, iodine-doped g-C₃N₄ (ICN) is introduced into ZnTiO₃-based ETL as additive via a glass-assisted annealing route. Characterizations demonstrate that the ZnTiO₃-based ETL with the addition of ICN will enhance the PCE, which is attributed to the improved crystalline quality and more favorable energy level alignment. Moreover, the existence of ICN will strengthen the interfacial cohesion between perovskite layer and ETL as well as retard the perovskite crystals from decomposing, leading to the high quality capping light-harvesting layer upon ICN-modified ZnTiO₃ (ZTO-ICN) film. Consequently, a champion device fabricated with ZTO-ICN ETL achieves a maximum PCE of 19.17 % with an open circuit voltage (V_oc) of 1.012 V, a short-circuit current density (J_sc) of 26.32 mA cm^-2 and a fill factor (FF) of 0.720 under AM 1.5 G sunlight (100 mW cm^-2).