Open Access

Understanding how electrolyte composition influences the structural factors governing charge storage in Prussian Blue analogues (PBAs) requires clarifying the coupled effects of ion desolvation, structural disorder, and transport pathway connectivity. Here, we demonstrate that electrolyte identity induces structural disorder, which correlates with transport dispersion measured under identical electrochemical conditions. To establish this relationship, Fe-, Co-, and Ni-based hexacyanoferrate thin films were electrodeposited from chloride electrolytes (KCl, NaCl, NH4Cl, and LiCl), enabling a comparative investigation of structure–transport correlations across multiple length scales. Although all systems crystallize in the cubic PBA structure, pronounced electrolyte-dependent variations in lattice parameters, defect concentration, and local coordination environments are observed. Na+ induces lattice expansion but simultaneously promotes vacancy formation, microstrain, and structural heterogeneity, whereas K+ and NH+4 produce more structurally coherent frameworks with reduced disorder. Raman spectroscopy reveals that increasing structural disorder broadens the distribution of local coordination environments, which is accompanied by increasingly dispersed electrochemical behavior. Electrochemical impedance spectroscopy reveals that charge storage is governed by coupled ion–electron transport processes, with the impedance increasing by more than one order of magnitude from FeHCF to NiHCF. Importantly, the constant phase element (CPE) exponent decreases systematically with increasing Raman band broadening, revealing a strong correlation between structural disorder and transport dispersion. These results demonstrate that electrolyte identity controls not only lattice dimensions but, more importantly, the organization and connectivity of defect networks. Consequently, optimal electrochemical performance arises from a balance between structural coherence and accessible transport pathways rather than from lattice expansion alone.

More than half a century of intense research in modern control theory has not stopped practitioners from continuing to use PID controllers for most real-world control problems. While not a mathematical one, this might be the most convincing proof of their robustness: if necessary, they can be implemented with minimal control engineering experience. Often, controllers are designed by individuals who are experts in their specific domain but are not dedicated control theory specialists. To address the needs of these engineers, this article wants to put an approach known as Active Disturbance Rejection Control (ADRC) in the spotlight—a method that has gradually evolved into an industry-ready alternative to PID control. Reflecting on two decades of improvements, this article portrays ADRC as a solution for everyday control problems that can be both easier to use and richer in out-of-the-box features.

This work investigates the optical stability of formamidinium–cesium lead halide perovskite thin films deposited on fluorine-doped tin oxide substrates and aged under ambient conditions for 21 days. The optical response was analyzed through specular and diffuse transmittance and reflectance measurements, collected with light incident from both sides of the heterostructure. Specular transmittance exhibits nonmonotonic variations with an initial increase followed by a gradual decrease over time, while diffuse transmittance increases systematically across the full spectral range, indicating the progressive formation of scattering centers. Total reflectance decreases monotonically with aging, revealing that degradation is primarily governed by absorption-related optical losses. Despite these changes, the absorption edge remains stable, and the optical bandgap and Urbach tail show no significant variation. Direction-dependent measurements demonstrate that the fluorine-doped tin oxide substrate is the dominant source of initial scattering whereas the perovskite layer initially reduces optical contrast and later introduces disorder as degradation progresses. Haze values remain nearly constant over time, indicating that changes in scattering efficiency are moderate compared to absorption losses. These results demonstrate that integrating sphere-based optical spectroscopy provides a nondestructive and effective framework for monitoring early stage degradation in perovskite thin films.