Enhancing the Optical Properties of MAPbI ₃ Perovskites Passivated with Coordinating and Hydrogen Bond Donor Ligands

MAPbI3 (MA; methylammonium) perovskite films were treated with both fluorinated (trifluoroacetamidine, TFA, and trifluoroacetamide, TFAM) and nonfluorinated (oxamide, Oxa) hydrogen bond donors as additives. The corresponding films named Oxa-MAPbI3, TFA-MAPbI3, and TFAM-MAPbI3 were thoroughly characterized to evaluate the influence of the type of additive on the structure, morphology, thermal stability, and optical properties of the resulting films. Powder X-ray diffraction (PXRD) studies confirmed the preservation of the MAPbI3 perovskite structure for the three types of additives. The decomposition kinetics at 100 °C in air highlight the high thermal stability of the TFAM-MAPbI3 film, compared to the behavior of films treated with other additives. An increase in binding energy was observed by XPS for the additives owing to their perturbation of Pb2+. MAPbI3 perovskite films containing different additives exhibited similar emissions as the MAPbI3 pristine films; however, their excited-state lifetimes were increased by roughly 40%.