Controlled Formation and AFM Monitoring of Active Layers of Hybrid Perovskites for Solar Cells

Abstract

This paper presents the results of a study on the controlled formation and comprehensive diagnostics of hybrid halide perovskite films for use in solar energy. The main focus is on the development of a technological approach that allows for targeted control of the morphology of the active layer at the synthesis stage. Films of the composition CH₃NH₃PbI₃ (MAPbI₃) modified with monoethanolammonium lead iodide (HOC₂H₄NH₃PbI₃, MEAPbI₃) additives were obtained by centrifugation from dimethylformamide (DMF)-based solutions). It was shown that the electrophysical characteristics, correlating with the experimental values of the fractal dimension, change with changing the concentration of additives and effects on the fractal dimension. Varying the additive concentration of the (0–70%) made it possible to determine the optimal ratio of components (MA_0.8MEA_0.2PbI₃), which provides a significant improvement in the wettability of the precursor on a glass substrate (a decrease in of the contact angle from ~20° to ~12°) without a significant change in the optical band gap (~1.6 eV). Using contact mode atomic force microscopy (AFM) and scanning spreading resistance scanning microscopy (SSRM), it was shown for the first time that the MEAI additive induces the formation of a hierarchical surface with a fractal dimension of 2.21, which corresponds to the formation of a quasi 2D/3D structure. It was found that the boundaries of the elements of this fractal structure have increased resistance, creating a system of barriers for the diffusion of ions. Thus, the article proposes a solution to an important problem related to increasing the stability of perovskite solar cells through targeted control of the active layer morphology at the stage of its synthesis. The proposed approach and set of diagnostic methods represent an effective tool for developing new perovskite materials with controlled properties and increased operational stability for solar energy applications.