Triazine-Substituted Zinc Porphyrin as an Electron Transport Interfacial Material for Efficiency Enhancement and Degradation Retardation in Planar Perovskite Solar Cells

Motivated by the excellent electron-transfer capability of porphyrin molecules in natural photosynthesis, we introduce here the first application of a porphyrin compound to improve the performance of planar perovskite solar cells. The insertion of a thin layer consisting of a triazine-substituted Zn porphyrin between the TiO₂ electron transport layer and the CH₃NH₃PbI₃ perovskite film significantly augmented electron transfer toward TiO₂ while also sufficiently improved the morphology of the perovskite film. The devices employing porphyrin-modified TiO₂ exhibited a significant increase in the short-circuit current densities and a small increase in the fill factor. As a result, they delivered a maximum power conversion efficiency (PCE) of 16.87% (average 14.33%), which represents a 12% enhancement compared to 15.01% (average 12.53%) of the reference cell. Moreover, the porphyrin-modified cells exhibited improved hysteretic behavior and a higher stabilized power output of 14.40% compared to 10.70% of the reference devices. Importantly, nonencapsulated perovskite solar cells embedding a thin porphyrin interlayer showed an elongated lifetime retaining 86% of the initial PCE after 200 h, while the reference devices exhibited higher efficiency loss due to faster decomposition of CH₃NH₃PbI₃ to PbI₂