Deep‐Level Transient Spectroscopy for Effective Passivator Selection in Perovskite Solar Cells to Attain High Efficiency over 23%

Abstract Most studies choose passivators essentially in a trial‐and‐error fashion in an attempt to attain high efficiency in perovskite solar cells (PSCs). Using deep‐level transient spectroscopy (DLTS) measurements, the type of defects in perovskite films was determined to guide the passivator selection for PSCs. Three kinds of positively charged defects were found in the target PSC system. Fluorinated phenylethylamine hydroiodide (FPEAI) was chosen to passivate the surface defects due to the electronegativity and hydrophobicity of fluorine. Due to the decreased surface roughness, increased hydrophobicity, lowered defect density, and improved carrier dynamics as observed by ultrafast transient absorption spectroscopy (TAS), a PSC with meta ‐F‐PEAI had the best efficiency over 23 % with open‐circuit voltage of 1.155 V and fill factor of 80.15 %. In addition, the long‐term stability of the PSC was significantly improved. The present work provides a new means to select the best passivator for different types of defects.