An Exploration of the Role of Acetamidinium Substitution in Methylammonium Lead Iodide Perovskites

Halide perovskite (HP) versatility for optoelectronic and electrochemical applications is mainly due to their ability to engineer cation mixtures at the A-site within the ABX₃ stoichiometry. Acetamidinium (AC⁺) is a common cation used in these mixed compositions, but its effects on the material's properties have not been addressed in detail. In this work, prototypical methylammonium lead iodide (MAPbI₃) compositions partially substituted with AC⁺ are synthesized and analyzed for structural, electrical, optoelectronic, and stability properties. Results reveal a solubility limit of around 10% AC⁺, lower than encountered in the literature, with slight effects on the phase transition temperatures. As expected, substitution with AC⁺ significantly reduces electronic conductivity and I-V hysteresis but only marginally increases the bandgap energy. Contrary to literature results, light-accelerated degradation tests show that AC⁺ incorporation does not significantly enhance the materials' stability. Among several reasons, this might be related to weak interactions between AC⁺ cations and the inorganic framework. This study establishes the effects of AC⁺ substitution in halide perovskites and provides insights into optimizing A-site compositions for optoelectronic and electrochemical applications.