Surface Modification of Cs_0.1(CH₃NH₃)_0.9PbI₃ by Isopropanol as Green Antisolvent for Efficiency Enhancement of Perovskite Solar Cells

Abstract

Surface modification of Cs0.1(CH3NH3)0.9PbI3 is investigated by antisolvent‐assisted crystallization (ASAC). The perovskite solar cells (PSCs) of FTO/SnO2/Cs0.1(CH3NH3)0.9PbI3/spiro‐OMeTAD/Ag are also fabricated. It is found that isopropanol‐treated devices exhibit a power conversion efficiency (PCE) of 16.3%, which is higher than chlorobenzene‐ (11.5%) and toluene‐treated devices (12.8%). The efficiency enhancement by isopropanol treatment can be attributed to better surface coverage, larger grain size, and less pinholes confirmed by scanning electron microscopy (SEM) and X‐rays diffraction (XRD) results, indicating an increase in short‐circuit current density (Jsc). In addition, the increase in open‐circuit voltage (Voc) can be confirmed by photoluminescence (PL) spectra, which can be suggested to the reduce the nonradiative recombination loss in the isopropanol‐treated film. The wettability of perovskite films is studied by contact angle measurement, resulting in a higher hydrophobic surface from isopropanol‐treated devices. Also, the charge dynamic behavior of PSC devices is investigated by open‐circuit voltage decay (OCVD) measurement. It is found that the charge carrier lifetime of the isopropanol‐treated device is longer than that of chlorobenzene and toluene. Therefore, surface modification of perovskite by isopropanol treatment can enhance efficiency and isopropanol can be used as an alternative green antisolvent for the perovskite process.