Synergistic stabilization of CsPbI3 inorganic perovskite via 1D capping and secondary growth

Cesium lead iodide (CsPbI3) perovskite has gained great attention in the photovoltaic (PV) community because of its unique optoelectronic properties, good chemical stability and appropriate bandgap for sunlight harvesting applications. However, compared to solar cells fabricated from organic-inorganic hybrid perovskites, the commercialization of devices based on all-inorganic CsPbI3 perovskites still faces many challenges regarding PV performance and long-term stability. In this work, we discovered that tetrabutylammonium bromide (TBABr) post-treatment to CsPbI3 perovskite films could achieve synergistic stabilization with both TBA+ cation intercalation and Br-doping. Such TBA+ cation intercalation leads to one-dimensional capping with TBAPbI3 perovskite formed in situ, while the Br-induced crystal secondary growth helps effectively passivate the defects of CsPbI3 perovskite, thus enhancing the stability. In addition, the incorporation of TBABr can improve energy-level alignment and reduce interfacial charge recombination loss for better device performance. Finally, the highly stable TBABr-treated CsPbI3-based perovskite solar cells show reproducible photovoltaic performance with a champion efficiency up to 19.04%, while retaining 90% of the initial efficiency after 500 h storage without encapsulation.