A Multi-Electron Transporting Layer for Efficient Perovskite Solar Cells

In this work, a multi-electron transporting layer (ETL) for efficient perovskite solar cells is investigated. The multi-ETL consists of five conditions including SnO2, SnO2/SnOx, TiO2, TiO2/SnO2, and TiO2/SnO2/SnOx. The best performance of PSC devices is found in the SnO2/SnOx double-layer and exhibits a power conversion efficiency equal to 18.39% higher than the device with a TiO2 single-layer of 14.57%. This enhancement in efficiency can be attributed to a decrease in charge transport resistance (Rct) and an increase in charge recombination resistance (Rrec). In addition, Rct and Rrec can be used to explain the comparable power conversion efficiency (PCE) between a PSC with a SnO2/SnOx double-layer and a PSC with a triple-layer, which is due to the compensation effect of Rct and Rrec parameters. Therefore, Rct and Rrec are good parameters to explain the efficiency enhancement in PSC. Thus, the Rct and Rrec from the electrochemical impedance spectroscopy (EIS) technique is an easy and alternative way to obtain information to understand and characterize the multi-ETL on PSC