Liq interlayer as electron extraction layer for highly efficient and stable perovskite solar cells

Summary Halide perovskite solar cells (PSCs) have gained enormous attention due to their favorable features such as bandgap tunability, considerable free carrier diffusion length, low‐cost fabrication, and comparable efficiency to that of conventional silicon solar cells. Among several PSCs' structures, the inverted structure is the most suitable candidate for diverse portable applications since they can take advantage of the previously developed organic solar cells' structure. However, the single transporting layer system of the inverted‐structured PSCs makes it challenging to achieve high efficiency and operational stability. Here, we introduce a unique transporting layer system that adopts 8‐hydroxyquinolinolato‐lithium (Liq) as a buffer layer at the interface between [6,6]‐phenyl C71 butyric acid methyl ester (PC70BM) and Ag electrode. By introducing the Liq, we effectively decreased the potential energy barrier and iodide accumulation at the interface between PC70BM and Ag electrode, which resulted in an efficient and stable PSC. In the optimized structure, the power conversion efficiency and stability (T80) increased from 9.5% and 100 h to 10.13% and 200 h, respectively. This article reports a unique electron extraction system that adopts 8‐hydroxyquinolinolato‐lithium (Liq) to improve the photovoltaic performance of perovskite solar cells. We have provided deep insights into the physical characteristics of the functional layer by investigating atomic force microscopy and scanning Kelvin probe microscopy. Furthermore, stability improvement of Liq adopted cells was investigated through an atomic distribution analysis.