High-Efficiency, Hysteresis-Less, UV-Stable Perovskite Solar Cells with Cascade ZnO–ZnS Electron Transport Layer

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Abstract
Perovskite solar cells (PSCs) have reached certified efficiencies of up to 23.3% but suffered from frailness and instability when exposed to ambient atmosphere. Zinc oxide (ZnO), when used as electron transport layer (ETL) on PSCs, gives rise to excellent electronic, optic and photonic properties, yet the Lewis basic nature of ZnO surface leads to deprotonation of the perovskite layer, resulting in serious degradation of PSCs using ZnO as ETL. Here, we report a simple but effective strategy to convert ZnO surface into ZnS at the ZnO/perovskite interface by sulfida-tion. The sulfide on ZnO-ZnS surface binds strongly with Pb2+ and creates a novel pathway of electron transport to accelerate electron transfer and reduce interfacial charge recombination, yielding a champion efficiency of 20.7% with improved stability and no appreciable hysteresis. The model devices modified with sulfide maintained 88% of their initial performance for 1,000 h under storage condition and 87% for 500 h under UV radiation. ZnS is demonstrated to act as both a cascade ETL and a passivating layer for enhancing the performance of PSCs.
Funding Information
  • Ministry of Education of the People's Republic of China (20720180061)
  • Ministry of Science and Technology of the People's Republic of China (2017YFA0207302)
  • National Natural Science Foundation of China (21721001, 21805232, 21420102001, 21731005)

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